Progress 10/01/03 to 09/30/08
Outputs
OUTPUTS: We have demonstrated that PKL promotes the repressive epigenetic mark trimethylation of lysine 27 histone H3 (H3K27me3). We have shown that PKR2, a homolog of PKL only expressed in seeds, prevents premature expression of seed-associated developmental programs. PARTICIPANTS: Joe Ogas (PI) Heng Zhang (graduate student) TARGET AUDIENCES: Biochemists PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Our studies reveal that plant CHD3 remodeling factors affect gene expression via a mechanism that is distinct from that characterized for animal CHD3 proteins. We are now in the process of determining how PKL contributes to deposition of H3K27me3. This work may lead to novel strategies to controlling gene expression in plants and/or to new insights into regulation of gene expression in animal systems.
Publications
- Zhang H, Rider SD, Henderson J, Fountain M, Chuang K, Kandachar K, Simons A, Edenberg HJ, Romero-Severson J, Muir WM, and Ogas J (2008). The CHD3 remodeler PICKLE promotes trimethylation of histone H3 lysine 27. J Biol Chem 283:22637
|
Progress 10/01/06 to 09/30/07
Outputs
OUTPUTS: We have demonstrated that PKL and GA act in separate pathways to repress expression of seed-associated genes during germination. We have shown that PKL interacts with histone tails. We have produced full-length recombinant PKL and shown that it is a nucleosome-stimulated ATPase.
PARTICIPANTS: Joe Ogas (PI) Heng Zhang (graduate student) Yinglin Bai (research associate)
Impacts
Our studies indicate that plant CHD3 remodeling factors affect gene expression via a mechanism that is distinct from that characterized for animal CHD3 proteins. We are now in the process of characterizing this mechanism. This mechanism may lead to novel strategies to controlling gene expression in plants and/or to new insights into regulation of gene expression in animal systems.
Publications
- Ogas J (2007). Preface to special issue on plant chromatin: Structure and expression. Biochim Biophys Acta 1769:267-8.
- Muir WM, Romero-Severson J, Rider SD, Simons A, and Ogas J (2006). Application of One Sided t-tests and a Generalized Experiment Wise Error Rate to High-Density Oligonucleotide Microarray Experiments: An Example Using Arabidopsis. J Data Sci 4:323.
|
Progress 10/01/05 to 09/30/06
Outputs
We have demonstrated that PKL and GA act in a synergistic fashion to repress expression of seed-associated genes during germination. We have shown that PKL primarily exists as a monomer in planta. We have produced full-length recombinant PKL that is biochemically active.
Impacts
We now know how GA levels affect expression of embryonic traits in pkl seedlings. As a result, we are now in a position to start studying the affect of GA on gene expression during germination. We are also now in a position to undertake biochemical characterization of the PKL remodeling factor. Our studies indicate that plant CHD3 remodeling factors affect gene expression via a mechanism that is distinct from that characterized for animal CHD3 proteins.
Publications
- Li H-C, Chuang K., Henderson J. T., Rider S. D. Jr., Bai Y., Zhang H., Fountain M., Gerber J. and Ogas J. PICKLE acts during germination to repress expression of embryonic traits. Plant J. 44:1010 (2005).
|
Progress 10/01/04 to 09/30/05
Outputs
We have generated an inducible version of PKL, the first time this feat has been accomplished for a CHD3 chromatin remodeling factor. We used this inducible version to demonstrate that PKL acts during germination to repress the ability of the plant to express embryonic traits. We also used the inducible version of PKL to demonstrate that the shoot phenotype of mutant pkl plants is due to the action of PKL after germination; i.e. that PKL's role during germination as a repressor of embryonic traits does not appear to contribute substantially to PKL's role during subsequent development of the shoot. We also found that PKL acts continuously in the shoot to repress expression of PHE1, a transcription factor normally expressed in developing seeds. Thus we have shown that PKL acts at multiple points in the life cycle of the plant to regulate plant growth and development.
Impacts
We have now demonstrated when PKL acts to repress embryonic traits. Thus, we now know when to undertake the necessary biochemistry to determine the mechanism by which PKL acts to facilitate this critical developmental switch.
Publications
- Falcone DL, Ogas JP, and Somerville CR (2004) Regulation of membrane fatty acid composition by temperature in mutants of Arabidopsis with alterations in membrane lipid composition. BMC Plant Biology 4:17.
|
Progress 10/01/03 to 09/29/04
Outputs
In the pickle (pkl) mutant of Arabidopsis, the primary root can fail to differentiate properly and continue to express embryonic differentiation characteristics after germination. Primary roots from pkl plants that continue to express embryonic differentiation characteristics are referred to as "pickle roots". Expression of the pickle root phenotype is dependent on the plant hormone gibberellin (GA). In addition, GA responses are altered in the pkl mutant, suggesting that PKL is involved in GA signal transduction. We have three main objectives: We will determine the role of PKL. We will investigate how the pickle root phenotype is generated. We will identify factors and mechanisms involved in GA signal transduction and/or in regulation of plant cell identity. Previous observations have also suggested that PKL mediates some aspects of GA responsiveness in the adult plant. To investigate possible mechanisms by which PKL and GA might act to repress the embryonic state,
we further characterized the ability of PKL and GA to repress embryonic traits and reexamined the role of PKL in mediating GA-dependent responses. We found that PKL acts throughout the seedling to repress expression of embryonic traits. Although the ability of pkl seedlings to express embryonic traits is strongly induced by inhibiting GA biosynthesis, it is only marginally responsive to abscisic acid (ABA) and SPINDLY (SPY), factors that have previously been demonstrated to inhibit GA-dependent responses during germination. We also observed that pkl plants exhibit the phenotypic hallmarks of a mutation in a positive regulator of a GA response pathway including reduced GA responsiveness and increased synthesis of bioactive GAs. These observations indicate that PKL may mediate a subset of GA-dependent responses during shoot development. In an attempt to examine the breadth of PKL-dependent repression of embryo-specific differentiation pathways, we determined the extent to which a
variety of embryo-specific compounds accumulate in pickle roots. We found that pickle roots accumulate triacylglycerol (TAG) with a fatty acid composition that is similar to that found in seeds. The major seed storage proteins are also present in pickle roots. In addition to these two well-characterized seed storage compounds, we observed that pickle roots accumulate phytate, a form of stored phosphate that is preferentially accumulated in seeds. Surprisingly, the levels of secondary metabolites in pickle roots were not suggestive of an embryonic differentiation state, but did reveal that a mutation in PKL results in substantial changes in root secondary metabolism. Taken together, these data suggest that PKL is responsible for regulating some but not all aspects of the embryonic program as it relates to the accumulation of embryo-specific metabolites.
Impacts
The intent of the proposed experiments is to elucidate the role of PKL and to identify factors and mechanisms that govern GA signal transduction and developmental transitions in plants. Insight gained from these studies may be useful in increasing agricultural productivity and / or in the generation of new crops. The genes that we have identified as exhibiting PKL-dependent transcriptional regulation during germination may be novel regulators of embryonic identity that have the potential to be utilized to modify important agronomic characteristics of seed crops. In particular, we are testing the hypothesis that we may have identified positive regulators of seed oil accumulation. In addition, the demonstration that PKL functions during germination now allows us to focus our efforts during this developmental time to engineer new traits into crops through expression of modified forms of PKL.
Publications
- Rider, S.D., Henderson, J.T., Jerome, R.E., Edenberg, H.J., Romero-Severson, J., and Ogas, J. Coordinate repression of regulators of embroyonic identity by PICKLE during germination in Arabidopsis The Plant Journal 35: 33-43. (2003)
- Henderson JT, Li H-C, Rider SD, Mordhorst AP, Romero-Severson J, Cheng J-C, Robey J, Sung ZR, de Vries SC, and Ogas J Pickle acts throughout the plant to repress expression of embryonic traits and may play a role in gibberellin-dependent responses Plant Physiology 134: 995-1005 (2004)
- Rider Jr SD, Hemm MR, Hostetler HA, Li H-C, Chapple C, and Ogas J Metabolic profiling of the Arabidopsis pkl mutant reveals selective derepression of embryonic traits Planta 219: 480-499 (2004)
- Hemm, M.R., Rider, S.D., Ogas, J., Murry, D.J., and Chapple, C. Light induces phenylpropanoid metabolism in Arabidopsis roots Plant J. 38: 765-778 (2004)
|
Progress 10/01/02 to 09/30/03
Outputs
OBJECTIVES: In the pickle (pkl) mutant of Arabidopsis, the primary root can fail to differentiate properly and continue to express embryonic differentiation characteristics after germination. Primary roots from pkl plants that continue to express embryonic differentiation characteristics are referred to as "pickle roots". Expression of the pickle root phenotype is dependent on the plant hormone gibberellin (GA). In addition, GA responses are altered in the pkl mutant, suggesting that PKL is involved in GA signal transduction. We have three main objectives: We will determine the role of PKL. We will investigate how the pickle root phenotype is generated. We will identify factors and mechanisms involved in GA signal transduction and/or in regulation of plant cell identity. APPROACH: Molecular biology, biochemistry, genomics, and genetics will be utilized to address the stated objectives. We have identified new factors involved in GA signal transduction and/or regulation
of cell identity through genomic and genetic screens and are using the tools of molecular biology and biochemistry to determine the function of these new factors. PROGRESS: 2000/10 TO 2001/09 We have demonstrated that PKL does function during germination to repress embryonic traits. We have used microarrays to identify over 700 genes that exhibit PKL-dependent transcription during germination. Many of these genes are preferentially expressed in embryos. Observations to date suggest that we have identified novel regulators of embryonic development that may be directly regulated by PKL. Experiments to test these hypotheses are underway. We have also identified mutants that are defective in perception of GA with respect to repression of embryonic identity. One mutant in particular, kissing cotyledon1 (kic1), exhibits a delayed germination phenotype that is consistent with a positive role in GA response. We are further characterizing the phenotype of kic1 plants and trying to clone the
wild-type locus based on its map position.
Impacts
The intent of the proposed experiments is to elucidate the role of PKL and to identify factors and mechanisms that govern GA signal transduction and developmental transitions in plants. Insight gained from these studies may be useful in increasing agricultural productivity and / or in the generation of new crops. The genes that we have identified as exhibiting PKL-dependent transcriptional regulation during germination may be novel regulators of embryonic identity that have the potential to be utilized to modify important agronomic characteristics of seed crops. In particular, we are testing the hypothesis that we may have identified positive regulators of seed oil accumulation. In addition, the demonstration that PKL functions during germination now allows us to focus our efforts during this developmental time to engineer new traits into crops through expression of modified forms of PKL.
Publications
- Rider, S.D., Henderson, J.T., Jerome, R.E., Edenberg, H.J., Romero-Severson, J., and Ogas, J. 2003. Coordinate repression of regulators of embroyonic identity by PICKLE during germination in Arabidopsis The Plant Journal 35: 33-43.
|
Progress 10/01/01 to 09/30/02
Outputs
OBJECTIVES: In the pickle (pkl) mutant of Arabidopsis, the primary root can fail to differentiate properly and continue to express embryonic differentiation characteristics after germination. Primary roots from pkl plants that continue to express embryonic differentiation characteristics are referred to as "pickle roots". Expression of the pickle root phenotype is dependent on the plant hormone gibberellin (GA). In addition, GA responses are altered in the pkl mutant, suggesting that PKL is involved in GA signal transduction. We have three main objectives: We will determine the role of PKL. We will investigate how the pickle root phenotype is generated. We will identify factors and mechanisms involved in GA signal transduction and/or in regulation of plant cell identity. APPROACH: Molecular biology, biochemistry, and genetics will be utilized to address the stated objectives. In general, we will identify new factors involved in GA signal transduction and/or regulation
of cell identity through genetic screens and then use the tools of molecular biology and biochemistry to determine the function of these new factors. PROGRESS: We have used microarrays to identify genes that exhibit PKL-dependent transcription during germination. Some of these genes are known regulators of embryo development, in particular the LEAFY COTYLEDON (LEC) genes, whereas other genes may be novel regulators of embryonic identity. In particular, we have identified a transcriptional regulator that exhibits PKL-dependent transcription that is preferentially expressed in developing siliques. Thus evidence to date suggests that we have identified novel regulators of embryonic development that may be directly regulated by PKL. Experiments to test these hypotheses are underway. We have also identified mutants that are defective in perception of GA with respect to repression of embryonic identity. The implication of this finding is that we may have identified genes that are involved
in GA signal transduction. We are now attempting to clone these genes.
Impacts
The intent of the proposed experiments is to elucidate the role of PKL and to identify factors and mechanisms that govern GA signal transduction and developmental transitions in plants. Insight gained from these studies may be useful in increasing agricultural productivity and / or in the generation of new crops. The genes that we have identified as exhibiting PKL-dependent transcriptional regulation during germination may be novel regulators of embryonic identity that have the potential to be utilized to modify important agronomic characteristics of seed crops. In addition, transgenic strategies employing these genes may be useful in obtaining embryogenic explants from crops that are typically recalcitrant to such experimental manipulation.
Publications
- No publications reported this period
|
Progress 10/01/00 to 09/30/01
Outputs
In the pickle (pkl) mutant of Arbabidopsis, the primary root can fail to differentiate properly and continue to express embryonic differentiation characteristics after germination. Primary roots from pkl plants that continue to express embryonic differentiation characteristics are referred to as "pickle roots". Expression of the pickle root phenotype is dependent on the plant hormone gibberellin (GA). In addition, GA responses are altered in the pkl mutant, suggesting that PKL is involved in GA signal transduction. We have three main objectives: We will determine the role of PKL. We will investigate how the pickle root phenotype is generated. We will identify factors and mechanisms involved in GA signal transduction and / or in regulation of plant cell identity.
Impacts
The intent of the proposed experiments is to elucidate the role of PKL and to identify factors and mechanisms that govern GA signal transduction and developmental transitions in plants. Insight gained from these studies may be useful in increasing agricultural productivity and / or in the generation of new crops.
Publications
- No publications reported this period
|
Progress 10/01/99 to 09/30/00
Outputs
In the pickle (pkl) mutant of Arabidopsis, the primary root can fail to differentiate properly and continue to express embryonic differentiation characteristics after germination. Primary roots from pkl plants that continue to express embryonic differentiation characteristics are referred to as "pickle roots". Expression of the pickle root phenotype is dependent on the plant hormone gibberellin (GA). In addition, GA responses are altered in the pkl mutant, suggesting that PKL is involved in GA signal transduction. We have three main objectives: We will determine the role of PKL. We will investigate how the pickle root phenotype is generated. We will identify factors and mechanisms involved in GA signal transduction and/or in regulation of plant cell identity.
Impacts
The intent of the proposed experiments is to elucidate the role of PKL and to identify factors and mechanisms that govern GA signal transduction and developmental transitions in plants Insight gained from these studies may be useful in increasing agricultural productivity and/or in the generation of new crops.
Publications
- Ogas, Joe: "Gibberellins" Current Biology 10:2 2000.
|
Progress 10/01/98 to 09/30/99
Outputs
In the pickle (pkl) mutant of Arabidopsis, the primary root can fail to differentiate properly and continue to express embryonic differentiation characteristics after germination. Primary roots from pkl plants that continue to express embryonic differentiation characteristics are referred to as "pickle roots". Expression of the pickle root phenotype is dependent on the plant hormone gibberellin (GA). In addition, GA responses are altered in the pkl mutant, suggesting that PKL is involved in GA signal transduction. We have three main objectives: We will determine the role of PKL. We will investigate how the pickle root phenotype is generated. We will identify factors and mechanisms involved in GA signal transduction and/or in regulation of plant cell identity.
Impacts
The intent of the proposed experiments is to elucidate the role of PKL and to identify factors and mechanisms that govern GA signal transduction and developmental transitions in plants Insight gained from these studies may be useful in increasing agricultural productivity and/or in the generation of new crops.
Publications
- Joe Ogas, Jin-Chen Cheng, S. Renee Sung, and Chris Somerville: Cellular Differentiation Regulated by Gibberline in the Arabidopsis thaliana pickle Mutant, American Association for the Advancement of Science 277:91-94 (1997)
- Ogas, J., Kaufmann, S., Henderson, J., Somerville, C. (1999) PICKLE is a chromatin remodeling factor that regulates the transition from embryonic to vegetative development in Arabidopsis. Proc. Natl. Acad. Sci. 96:13839-13844
|
|