Progress 10/01/08 to 09/30/13
Outputs
OUTPUTS: Mutation of the ECERIFERUM9 (CER9) gene in Arabidopsis (Arabidopsis thaliana) causes elevated amounts of 18-carbon-length cutin monomers and a dramatic shift in the cuticular wax profile (especially on leaves) toward the very-long-chain free fatty acids tetracosanoic acid (C24) and hexacosanoic acid (C26). Relative to the wild type, cer9 mutants exhibit elevated cuticle membrane thickness over epidermal cells and cuticular ledges with increased occlusion of the stomatal pore. The cuticular phenotypes of cer9 are associated with delayed onset of wilting in plants experiencing water deficit, lower transpiration rates, and improved water use efficiency measured as carbon isotope discrimination. The CER9 protein thus encodes a novel determinant of plant drought tolerance-associated traits, one whose deficiency elevates cutin synthesis, redistributes wax composition, and suppresses transpiration. Map-based cloning identified CER9, and sequence analysis predicted that it encodes an E3 ubiquitin ligase homologous to yeast Doa10 (previously shown to target endoplasmic reticulum proteins for proteasomal degradation). To further elucidate CER9 function, the impact of CER9 deficiency on interactions with other genes was examined using double mutant and transcriptome analyses. For both wax and cutin, cer9 showed mostly additive effects with cer6, long-chain acyl-CoA synthetase1 (lacs1), and lacs2 and revealed its role in early steps of both wax and cutin synthetic pathways. Transcriptome analysis revealed that the cer9 mutation affected diverse cellular processes, with primary impact on genes associated with diverse stress responses. The discovery of CER9 lays new groundwork for developing novel cuticle-based strategies for improving the drought tolerance and water use efficiency of crop plants. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Molecular biologists and plant scientists. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Environmental challenges to plants typically entail retardation of vegetative growth and delay or cessation of flowering. Here we report a link between the flowering time regulator, GIGANTEA (GI), and adaptation to salt stress that is mechanistically based on GI degradation under saline conditions, thus retarding flowering. GI, a switch in photoperiodicity and circadian clock control, and the SNF1-related protein kinase SOS2 functionally interact. In the absence of stress, the GI:SOS2 complex prevents SOS2-based activation of SOS1, the major plant antiporter mediating adaptation to salinity. GI overexpressing, rapidly flowering, plants show enhanced salt sensitivity, whereas gi mutants exhibit enhanced salt tolerance and delayed flowering. Salt-induced degradation of GI confers salt tolerance by the release of the SOS2 kinase. The GI-SOS2 interaction introduces a higher order regulatory circuit that can explain in molecular terms, the long observed connection between floral transition and adaptive environmental stress tolerance in Arabidopsis.
Publications
- Barra L, Aiese-Cigliano R, Cremona G, De Luca P, Zoppoli P, Bressan RA, Consiglio FM, Conicella C (2012) Transcription profiling of laser microdissected microsporocytes in an Arabidopsis mutant (Atmcc1) with enhanced histone acetylation. J. Plant Biol 55:281-289.
- Kim W-Y, Ali Z, Park HJ, Park SJ, Cha J-Y, Perez-Hormaeche J, Quintero FJ, Shin G, Kim MR, Qiang Z, Ning L, Park HC, Lee SY, Bressan RA, Pardo JM, Bohnert HJ, Yun D-J (2012) Release of SOS2 kinase from sequestration with GIGANTEA determines salt tolerance in Arabidopsis. Nature Communications (In Press).
- Lu S, Zhao H, Des Marais DL, Parsons EP, Wen X, Xu X, Bangarusamy DK, Wang G, Rowland O, Juenger T, Bressan RA, Jenks MA (2012) Arabidopsis ECERIFERUM9 involvement in cuticle formation and maintenance of plant water status. Plant Physiol. 159:930-944.
- Xu Z-Y, Lee KH, Dong T, Jeong JC, Jin JB, Kanno Y, Kim DH, Kim SY, Seo M, Bressan RA, Yun D-J, Hwang I (2012) A vacuolar -glucosidase homolog that possesses glucose-conjugated abscisic acid hydrolyzing activity plays an important role in osmotic stress responses in Arabidopsis. Plant Cell 24:2184-2199
- Ali Z, Park HC, Ali A, Oh D-H, Aman R, Kropornicka A, Hong H, Choi W, Chung WS, Kim W-Y, Bressan RA, Bohnert HJ, Lee SY, Yun D-J (2012) TsHKT1;2, a HKT1 homolog from the extremophile Arabidopsis relative Thellungiella salsugienea, shows K+ specificity in the presence of NaCl. Plant Physiol. 158:1463-1474.
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Progress 10/01/10 to 09/30/11
Outputs
OUTPUTS: Dr. Ray Bressan was on medical leave during this reporting period. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Molecular biologists and basic plant scientists. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Manuscripts completed and submitted for review during previous reporting periods were published during this reporting period.
Publications
- Arsenescu V, Narasimhan ML, Halide T, Bressan RA, Barisione C, Cohen, DA, de Villiers WJS, Arsenescu R. 2011. Adiponectin and Plant-Derived Mammalian Adiponectin Homolog Exert a Protective Effect in Murine Colitis. Digestive Diseases and Sciences 56:2818-2832.
- Bressan RA, Reddy MP, Chung SH, Yun DJ, Hardin LS, Bohnert HJ. 2011. Stress-adapted extremophiles provide energy without interference with food production. Food Security 3:93-105.
- Choi W, Baek D, Oh DH, Park J, Hong H, Kim WY, Bohnert HJ, Bressan RA, Park HC, Yun DJ. 2011. NKS1, Na(+)- and K(+)-sensitive 1, regulates ion homeostasis in an SOS-independent pathway in Arabidopsis. Phytochemistry 72:330-336.
- Dassanayake M, Oh D-H, Haas, JS, Hernandez A, Hong H, Ali S, Yun DJ, Bressan RA, Zhu JK, Bohnert HJ, Cheeseman JM. 2011. The genome of the extremophile crucifer Thellungiella parvula. Nature Genetics 43:913-U137.
- Kim, JI, Murphy AS, Baek D, Lee SW, Yun DJ, Bressan RA, Narsimhan ML. 2011. YUCCA6 over-expression demonstrates auxin function in delaying leaf senescence in Arabidopsis thaliana. Journal of Experimental Botany 62:3981-3992.
- Lei M, Zhu C, Liu YD, Karthikeyan AS, Bressan RA, Raghothama KG, Liu D. 2011. Ethylene signalling is involved in regulation of phosphate starvation-induced gene expression and production of acid phosphatases and anthocyanin in Arabidopsis. New Phytologist 189:1084-1095.
- Park HC, Choi W, Park HJ, Cheong MS, Koo YD, Shin G, Chung WS, Kim WY, Kim MG, Bressan RA, Bohnert HJ, Lee SY, Yun DJ. 2011. Identification and molecular properties of SUMO-binding proteins in Arabidopsis. Molecules and Cells 32:143-151.
- Lu SY, Zhao HY, Parsons EP, Xu CC , Kosma DK, Xu XJ, Chao D, Lohrey G, Bangarusamy DK, Wang G, Bressan RA, Jenks MA. 2011. The glossyhead1 Allele of ACC1 Reveals a Principal Role for Multidomain Acetyl-Coenzyme A Carboxylase in the Biosynthesis of Cuticular Waxes by Arabidopsis. Plant Physiol. 157:1079-1092.
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Progress 10/01/09 to 09/30/10
Outputs
OUTPUTS: Salinity is an abiotic stress that limits both yield and the expansion of agricultural crops to new areas. In the last 20 years our basic understanding of the mechanisms underlying plant tolerance and adaptation to saline environments has greatly improved owing to active development of advanced tools in molecular, genomics, and bioinformatics analyses. However, the full potential of investigative power has not been fully exploited, because the use of halophytes as model systems in plant salt tolerance research is largely neglected. The recent introduction of halophytic Arabidopsis-Relative Model Species (ARMS) has begun to compare and relate several unique genetic resources to the well-developed Arabidopsis model. In a search for candidates to begin to understand, through genetic analyses, the biological bases of salt tolerance, 11 wild relatives of Arabidopsis thaliana were compared: Barbarea verna, Capsella bursa-pastoris, Hirschfeldia incana, Lepidium densiflorum, Malcolmia triloba, Lepidium virginicum, Descurainia pinnata, Sisymbrium officinale, Thellungiella parvula, Thellungiella salsuginea (previously T. halophila), and Thlaspi arvense. Among these species, highly salt-tolerant (L. densiflorum and L. virginicum) and moderately salt-tolerant (M. triloba and H. incana) species were identified. Only T. parvula revealed a true halophytic habitus, comparable to the better studied Thellungiella salsuginea. Major differences in growth, water transport properties, and ion accumulation are observed and discussed to describe the distinctive traits and physiological responses that can now be studied genetically in salt stress research. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Molecular biologists and basic plant scientists. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
A mutation of AtSOS1 (Salt Overly Sensitive 1), a plasma membrane Na+/H+-antiporter in Arabidopsis thaliana, leads to a salt-sensitive phenotype accompanied by the death of root cells under salt stress. Intracellular events and changes in gene expression were compared during a non-lethal salt stress between the wild type and a representative SOS1 mutant, atsos1-1, by confocal microscopy using ion-specific fluorophores and by quantitative RT-PCR. In addition to the higher accumulation of sodium ions, atsos1-1 showed inhibition of endocytosis, abnormalities in vacuolar shape and function, and changes in intracellular pH compared to the wild type in root tip cells under stress. Quantitative RT-PCR revealed a dramatically faster and higher induction of root-specific Ca2+ transporters, including several CAXs and CNGCs, and the drastic down-regulation of genes involved in pHhomeostasis and membrane potential maintenance. Differential regulation of genes for functions in intracellular protein trafficking in atsos1-1 was also observed. The results suggested roles of the SOS1 protein, in addition to its function as a Na+/H+ antiporter, whose disruption affected membrane traffic and vacuolar functions possibly by controlling pH homeostasis in root cells.
Publications
- Oh, D-H, Dassanayake m, Haas JS, Kropornika A, Wright C, d-Urzo, MP, Hong H, Ali S, Hernandez A, Lambert GM, Inan G, Galbraith DW, Bressan RA, Yun D-J, Zhu J-K, Cheeseman JM, Bohnert HJ (2010) Genome Structures and Halophyte-Specific Gene Expression of the Extremophile Thellungiella parvula in Comparison with Thellungiella salsuginea (Thellungiella halophila) and Arabidopsis. Plant Physiol 154:1040-1052.
- Kim H-S, Kim SJ, Abbasi N, Bressan RA, Yun D-J, Yoo S-D, Kwon S-Y, Choi S-B (2010) The DOF transcription factor Dof5.1 influences leaf axial patterning by promoting Revoluta transcription in Arabidopsis. Plant J 64:524-535.
- Park HC, Kim H, Koo SC, Park HJ, Cheong MS, Hong H, Baek D, Chung WS, Kim DH, Bressan RA, Lee SY, Bohnert HJ, Yun DJ (2010) Functional characterization of the SIZ/PIAS-type SUMO E3 ligases, OsSIZ1 and OsSIZ2 in rice. Plant Cell Environ 33:1923-1934.
- Orsini F; D'Urzo MP; Inan G, Serra S, Oh DH, Mickelbart MV, Consiglio F, Li X, Jeong JC, Yun DJ, Bohnert HJ, Bressan RA, Maggio A (2010) : A comparative study of salt tolerance parameters in 11 wild relatives of Arabidopsis thaliana. J Exp Bot 61:3787-3798.
- Zhu, JH; Verslues, PE; Zheng, XW, Lee Bh, Zhan XQ, Manabe Y, Sokolchik I, Zhu YM, Dong CH, Zhu JK, Hasegawa PM, Bressan RA (2010) HOS10 encodes an R2R3-type MYB transcription factor essential for cold acclimation in plants (Retraction of vol 102, 9966, 2005). Proc Natl Acad Sci USA 107:13972-13972.
- Perrella G, Consiglio MF, Aiese-Cigliano R, Cremona G, Sanchez-Moran E, Barra L, Errico A, Bresan RA, Franklin FCH, Conicella C (2010) Histone hyperacetylation affects meiotic recombination and chromosome segregation in Arabidopsis. Plant J 62:796-806.
- Lee H, Damsz B, Woloshuk CP, Bressan RA, Narasimhan ML (2010) Use of the plant defense protein osmotin to identify Fusarium oxysporum genes that control cell wall properties. Eukaryotic Cell 9:558-568.
- Oh D-H, Lee SY, Bressan RA, Yun D-J, Bohnert HJ (2010) Intracellular consequences of SOS1 deficiency during salt stress. J Exp Bot 61:1205-1213.
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Progress 10/01/08 to 09/30/09
Outputs
OUTPUTS: Dr. Ray A. Bressan has been on a special leave of absence from Purdue University during FY2009-10. There has been continued progress toward the principal goals of this project in terms of elucidating the genetic and biochemical mechanisms that confer stress tolerance in plants. This has derived primarily from the analysis of research data obtained during 2008 and subsequently published in 2009 (see below: Publications not previously reported). PARTICIPANTS: See "Outputs" TARGET AUDIENCES: See "Outputs" PROJECT MODIFICATIONS: See "Outputs"
Impacts
See "Outputs"
Publications
- Rosado A, Sohn EJ, Drakakaki G, Pan S, Swidergal A, Xiong Y, Kang BH, Bressan RA, Raikhel NV. 2010. Auxin-Mediated Ribosomal Biogenesis Regulates Vacuolar Trafficking in Arabidopsis. Plant Cell. Jan 8, 2010.
- Oh DH, Lee SY, Bressan RA, Yun DJ, Bohnert HJ. 2010. Intracellular consequences of SOS1 deficiency during salt stress. J Exp Bot. Jan 6, 2010.
- Cheong MS, Park HC, Hong MJ, Lee J, Choi W, Jin JB, Bohnert HJ, Lee SY, Bressan RA, Yun DJ. 2009. Specific domain structures control abscisic acid-, salicylic acid-, and stress-mediated SIZ1 phenotypes. Plant Physiol. 151(4):1930-42.
- Leidi EO, Barragan V, Rubio L, El-Hamdaoui A, Ruiz MT, Cubero B, Fernandez JA, Bressan RA, Hasegawa PM, Quintero FJ, Pardo JM. 2009. The AtNHX1 exchanger mediates potassium compartmentation in vacuoles of transgenic tomato. Plant J. Nov 14, 2009.
- Oh DH, Zahir A, Yun DJ, Bressan RA, Bohnert HJ. SOS1 and halophytism. 2009. Plant Signal Behav. 4(11):1081-3.
- Mang HG, Laluk KA, Parsons EP, Kosma DK, Cooper BR, Park HC, AbuQamar S, Boccongelli C, Miyazaki S, Consiglio F, Chilosi G, Bohnert HJ, Bressan RA, Mengiste T, Jenks MA. 2009. The Arabidopsis RESURRECTION1 gene regulates a novel antagonistic interaction in plant defense to biotrophs and necrotrophs. Plant Physiol. 151(1):290-305.
- Oh DH, Leidi E, Zhang Q, Hwang SM, Li Y, Quintero FJ, Jiang X, D'Urzo MP, Lee SY, Zhao Y, Bahk JD, Bressan RA, Yun DJ, Pardo JM, Bohnert HJ. 2009. Loss of halophytism by interference with SOS1 expression. Plant Physiol. 151(1):210-22.
- Quist TM, Sokolchik I, Shi H, Joly RJ, Bressan RA, Maggio A, Narsimhan M, Li X. 2009. HOS3, an ELO-like gene, inhibits effects of ABA and implicates a S-1-P/ceramide control system for abiotic stress responses in Arabidopsis thaliana. Mol Plant. 2(1):138-51.
- Hernandez A, Jiang X, Cubero B, Nieto PM, Bressan RA, Hasegawa PM, Pardo JM. 2009. Mutants of the Arabidopsis thaliana cation/H+ antiporter AtNHX1 conferring increased salt tolerance in yeast: the endosome/prevacuolar compartment is a target for salt toxicity. J Biol Chem. 284(21):14276-85.
- Cubero B, Nakagawa Y, Jiang XY, Miura KJ, Li F, Raghothama KG, Bressan RA, Hasegawa PM, Pardo JM. 2009. The phosphate transporter PHT4;6 is a determinant of salt tolerance that is localized to the Golgi apparatus of Arabidopsis. Mol Plant. 2(3):535-52.
- He XJ, Hsu YF, Pontes O, Zhu J, Lu J, Bressan RA, Pikaard C, Wang CS, Zhu JK. 2009. NRPD4, a protein related to the RPB4 subunit of RNA polymerase II, is a component of RNA polymerases IV and V and is required for RNA-directed DNA methylation. Genes Dev. 23(3):318-30.
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Progress 10/01/07 to 09/30/08
Outputs
OUTPUTS: Phenotypes associated with several stress sensitive mutants such as morphological, anatomical or developmental alterations will also be examined in the segregating F2 population. Many sensitive mutants from the F2 population displayed particular anatomical phenotype - and we have concluded that often anatomical and stress sensitive phenotypes are caused by the same mutation. Different mutant lines have been crossed pairwise to determine whether any of them are allelic. Mutants from different complementation groups also have been crossed to each other in order to construct double mutants. For appropriate phenotypic analyses of double mutants it appears that epistatic relationships between several genetic loci exist. Many mutant loci have been identified by Thermal asymmetric interlaced (TAIL)-PCR. We have already identified a number of loci in the salt cress insertion mutant population by this approach. Plasmid has been used as an alternative for isolating genes from T-DNA mutants. For this purpose, T-DNA include an E. coli replication origin. Plant DNA was extracted and digested with appropriate restriction enzymes for rescue of left- or right-border flanking DNA sequences. After digestion, reactions were subjected to phenol/chloroform and chloroform extractions and DNA was recovered by ethanol precipitation. Samples were then ligated and DNA aliquots were used for E. coli transformation by electroporation. Positive clones were selected on LB agar media containing 50 mg/L ampicillin. The rescued DNA was sequenced either from inside the left or the right borders. After using these methods, salt cress sequences obtained by TAIL-PCR or plasmid rescue were "Blasted" against the Arabidopsis database. In most cases, sequences matched Arabidopsis genes. cDNAs corresponding to cloned genes were obtained by library screening or reverse transcription-PCR. In some cases gene organization has been deduced by comparing genomic and cDNA sequences. The genome of salt cress is now being sequenced and this information is expected to be available in the next year or so. To confirm that a cloned gene is responsible for the mutant phenotype, mutant complementation was carried out. For this purpose, a cloned gene fragment provides a probe for screening the 'small insert' TAC library of salt cress. Several overlapping short TACs that cover the region of the gene of interest were introduced into mutant salt cress for complementation tests. Alternatively, we have used a cDNA clone obtained from cDNA library we have made from Thellungiella. Several genes have been identified in this way - including those encoding short chain dehydrogenase and a pyruvate kinase. PARTICIPANTS: Research was conducted by scientists in training and these individuals are identified as authors on published reports. TARGET AUDIENCES: Plant Biologists and Agriculturists PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
There has been a critical need for a halophytic genetic model system for salt tolerance research. The lack of such a model system has limited progress towards mechanistic understanding of salt tolerance in naturally salt tolerant plants. Halophytic plant systems such as the ice plant, Atriplex, Suaeda and Salicornia that have been studied are not amenable to either forward or reverse genetic analysis. Just like the Arabidopsis model system has revolutionized plant biology, the salt cress model system has the potential to revolutionize salt tolerance research. The value of salt cress is not limited to salt or drought tolerance research. This plant possesses several other traits that are of potential use to plant biologists. Its obligate requirement for vernalization makes it an attractive model to study control of flowering by low temperature. Features of salt cress root, leaf, silique and seed morphology or structure are of interest to researchers working on plant development. Salt cress seeds have been provided to a number of developmental biologists for detailed examination. As we develop the genetic infrastructure for salt cress, more biologists will use the plant in their studies. Because salt cress is a close relative of Arabidopsis and shares many of the features that have made Arabidopsis such an attractive model, studies on salt cress will be able to take full advantage of the genetic and genomic resources of Arabidopsis. As we enter a post-Arabidopsis era, it is important that we find ways to capitalize on the Arabidopsis resources. Salt cress is ideally suited for this purpose since all tools, protocols and the genetic infrastructure developed for Arabidopsis can be put to use. This project has greatly progressed the use of relatives of Arabidopsis to study various important agronomic traits. Some major agronomic traits such as extreme salt, drought, and cold or freezing tolerance, the obligate vernalization requirement, short day photoperiodism, biannualism and perrenialism are not present in Arabidopsis. However, these traits may be found in the various Arabidopsis relatives, which like salt cress can be amenable to genetic dissection. Genetics analysis in Arabidopsis relatives and the development of such a model system as we have done on this project could bring a post-Arabidopsis revolution to plant biology since the traits that can be studied will not be limited by Arabidopsis thaliana mutations or ecotype variations.
Publications
- Oh DH, Gong Q, Ulanov A, Zhang Q, Li Y, Ma W, Yun D-J, Bressan RA, Bohnert HJ (2007) Sodium stress in the halophyte Thellungiella halophila and transcriptional changes in a thsos1-RNA interference line. J Integr Plant Biol 49:1484-1483
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Progress 10/01/06 to 09/30/07
Outputs
OUTPUTS: A Thellungiella halophila T-DNA activation tagged population was screened for mutants with high germination capacity (hgc) under high NaCl stress and hgc1-1 was identified. hgc1-1 accumulates an elevated transcript that contains a putative ThHGC1 open reading frame (ORF). ThHGC1 encodes a putative pyruvate kinase (PK). ThHGC1 share high identity (98%) with AtHGC1, a homolog in Arabidopsis. Overexpression of AtHGC1 cDNA gene in Arabidopsis enhanced salt tolerance during germination of Wild-Type.
TARGET AUDIENCES: Plant Scientists working on Plant Stress.
Impacts
High salt inhibits seed germination and does harm to vegetative growth. Since T. halophila is very sensitive to salt stress during germination, several salt-tolerant lines have been generated in our lab by producing T-DNA activation tagged pools. Research on one line indicated that HGC/PK genes control seed germination responses to NaCl and ABA in plants. All plants have their PK protein copies. It is safe to generate elevated PK trascripts by using their native genes in, especially, crop plants to improve their ability of germination power under stresses.
Publications
- Maggio, A., J.K. Zhu, P.M. Hasegawa, R.A. Bressan. 2006. Osmogenetics: Aristotle to Arabidopsis. Historical Essay. Plant Cell 18:1542-1557
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Progress 10/01/05 to 09/30/06
Outputs
Accumulation and analysis of expressed sequence tags (ESTs) data from halophytic plant is a relatively rapid and cheap way for discovering new genes related to salinity tolerance. We constructed a NaCl-treated cDNA library of Thellungiella halophila and sequenced more than 1500 randomly selected clones. By sequence analysis, 813 unique clones were identified: 549 showed homology to previously identified genes, 264 matched uncharacterized genes. All our EST data are available on the Internet. The identity between T. halophila and Arabidopsis thaliana cDNA sequences in our EST collection are 95.76% in total ESTs and 95.36% in non-redundant clones. At least eight classes of genes were related to the salt-tolerance, which accounted for about 18.89% of total sequenced ESTs. T. halophila that has many features similar to Arabidopsis can be adopted as a halophytic model for stress-tolerance research.
Impacts
This project is expected to provide basic information regarding the molecular genetic bases of tolerance of plants to osmotic-based stresses including salinity, drought and freezing. Some genetic determinants controlling tolerance to these stresses have already been discovered and their usefulness in agricultural production should be determined in the next few years.
Publications
- Rus AM, Bressan RA, Hasegawa PM (2005) Unraveling salt tolerance in crops. Nature Genetics 37:1029-1030
- Shi HZ, Bressan RA, Hasegawa PM, Zhu J-K (2005) Sodium. Plant Nutritional Genomics. 127-149
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Progress 10/01/04 to 09/30/05
Outputs
We report the identification and characterization of an Arabidopsis mutant, hos10-1 (for high expression of osmotically responsive genes), in which the expression of RD29A and other stress-responsive genes is activated to higher levels or more rapidly activated than in wild-type by low temperature, exogenous abscisic acid (ABA), or salt stress (NaCl). The hos10-1 plants are extremely sensitive to freezing temperatures, completely unable to acclimate to the cold, and are hypersensitive to NaCl. Induction of NCED3 (the gene that encodes the rate-limiting enzyme in ABA biosynthesis) by polyethylene glycol-mediated dehydration and ABA accumulation are reduced by this mutation. Detached shoots from the mutant plants display an increased transpiration rate compared with wild-type plants. The hos10-1 plants exhibit several developmental alterations, such as reduced size, early flowering, and reduced fertility. The HOS10 gene encodes a putative R2R3-type MYB transcription
factor that is localized to the nucleus. Together, these results indicate that HOS10 is an important coordinating factor for responses to abiotic stress and for growth and development.
Impacts
This project is expected to provide basic information regarding the molecular genetic bases of tolerance of plants to osmotic-based stresses including salinity, drought and freezing. Some genetic determinants controlling tolerance to these stresses have already been discovered and their usefulness in agricultural production should be determined in the next few years.
Publications
- Zhu, J., P.E. Verslues, X. Zheng, B.-h. Lee, X. Zhan, Y. Manabe, I. Sokolchik, Y. Zhu, C.-H. Dong, J.-K. Zhu, P.M. Hasegawa, R.A. Bressan 2005. HOS10 encodes an R2R3-type MYB transcription factor essential for cold acclimation in plants. Proc. Natl. Acad. Sci. USA. 102:9966-9971.
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Progress 10/01/03 to 09/29/04
Outputs
Progress in discovering functional salt/osmotic and freezing tolerance mechanisms and genes that make halophytic and cryophytic species extremely well adapted to stress environments has been limited because of their marginal tractability for genetic analysis. The extremophile, Thellungiella halophila (salt cress) can complete its life cycle in seawater concentrations of NaCl and is capable of tolerating freezing temperature extremes. Salt cress provides the ideal salt/osmotic and freezing tolerant genetic model system because it is closely related to Arabidopsis. T. halophila EST sequences are more than 90% identical to those of Arabidopsis. Several other features add attractiveness to salt cress as a genetic model, e.g. small plant size, high seed yield, short life cycle and a small genome. Simple and efficient transformation through floral dipping has been achieved. Furthermore, we have identified several mutants from an EMS-mutagenized M2 population of salt cress
with similar salt sensitivity of Arabidopsis, indicating that individual loci may contribute to extreme tolerance of this plant species. We will identify on a genomic scale, salt tolerance genes from salt cress through loss-of-function genetic analyses by generating and screening T-DNA insertion lines. We will take advantage of an effective genetic transformation system to increase our collection of 35,000 T-DNA insertion mutant lines to at least 200,000. Salt-sensitive mutants will then be screened from the insertion lines and the corresponding tolerance genes cloned via a TAIL PCR, or a plasmid rescue approach. Substantial genetic, physiological, biochemical and morphological characterization of the salt cress mutants will then be performed to establish mechanisms that contribute to its capacity to tolerate extreme salt stress. Furthermore, since T. halophila is also freezing tolerant, our analyses may reveal common mechanistic determinants that make this extremophile tolerant to
both salt and freezing extremes.
Impacts
This project is expected to provide basic information regarding the molecular genetic bases of tolerance of plants to osmotic-based stresses including salinity, drought and freezing. Some genetic determinants controlling tolerance to these stresses have already been discovered and their usefulness in agricultural production should be determined in the next few years.
Publications
- Inan G, Zhang H, Li P, Wang Z, Cao Z, Zhang C, Quist TM, Goodwin SM, Zhu J, Shi H, Damsz B, Charbaji T, Gong Q, Ma S, Fredricksen M, Galbraith DW, Jenks MA, Rhodes D, Hasegawa PM, Bohnert HJ, Joly RJ, Bressan RA, Zhu J-K (2004) Salt Cress (Thellungiella halophila): A halophyte and cryophyte Arabidopsis relative model system (ARMS) and its applicability to molecular genetic analyses of growth and development of extremophiles. Plant Physiol 135:1718-1737
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Progress 10/01/02 to 09/30/03
Outputs
To investigate the essential components mediating stress signaling in plants, we initiated a large scale screen for stress response mutants using Arabidopsis plants that carry the firefly luciferase reporter gene under the control of the stress-responsive RD29A promoter. Several mutants have been identified and two have been characterized in detail. One of these is hos9-1 (for high expression of osmotically responsive genes), in which the RD29A::LUC was hyperactivated by low temperature, but not by abscisic acid (ABA), or salinity stress. The accumulation of transcripts of the endogenous RD29A gene and other stress responsive genes was hyperinduced in hos9-1 mutant plants compared to wild type plants. However, the CBF (CRT binding factor) transcription factor genes that mediate cold acclimation in Arabidopsis did not have altered expression in hos9-1 mutant plants. Microarray analysis revealed that none of the genes with expression that is disrupted by the hos9-1
mutation are controlled by the CBF family. The hos9-1 plants are substantially more sensitive to freezing treatment both before and after cold acclimation. The mutant plants also grow more slowly and flower later than wild type plants. The HOS9 gene encodes a putative homeodomain transcription factor that is localized to the nucleus. HOS9 is constitutively expressed and not further induced by cold stress. Together, these results suggest that HOS9 is important for plant growth and development, and freezing tolerance by affecting a signal pathway separate from that mediated by CBF. Another mutant, hos15-1 (for high expression of osmotically responsive genes), displays the super-induction of luminescence by low temperature, exogenous abscisic acid (ABA), or osmotic stress (NaCl). The expression of the endogenous RD29A and other stress responsive genes but not the stress-induced transcription regulator, CBF, was super-induced in the hos15-1 mutant plants compared to wild type plants. The
hos15-1 plants are more sensitive to freezing treatment. The seed germination of hos15-1 appears to be more sensitive to inhibition by ABA or NaCl. In addition, the hos15-1 plants flower late. The HOS15 locus was identified by TAIL-PCR and it encodes an unknown protein. Introducing the genomic fragment, which contains the wild type HOS15 gene into hos15-1 mutant plants complemented hos15-1 mutant phenotype. HOS15 is localized to the nucleus. Together, these results suggest that HOS15 is an important component of the stress signaling system of plants.
Impacts
This project is expected to provide basic information regarding the molecular genetic bases of tolerance of plants to osmotic-based stresses including salinity, drought and freezing. Some genetic determinants controlling tolerance to these stresses have already been discovered and their usefulness in agricultural production should be determined in the next few years.
Publications
- Koiwa, H. , F. Li, M. G. McCully, I. Mendoza, N. Koizumi, Y. Manabe, Y. Nakagawa, J. Zhu, A. Rus, J.M. Pardo, R.A. Bressan and P.M. Hasegawa. 2003. The STT3a Subunit Isoform of the Arabidopsis Oligosaccharyltransferase Controls Adaptive Responses to Salt/Osmotic Stress. Plant Cell. 15:2273-2284.
- Zhu-Salzman, K. , P. K. Hammen, R. A. Salzman, H. Koiwa, R.A. Bressan, L.L. Murdock and P.M. Hasegawa. 2002. Calcium modulates protease resistance and carbohydrate binding of a plant defense legume lectin, Griffonia simplicifolia lectin II (GSII). Comparative Biochemistry and Physiology Part B. 132:327-334.
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