Progress 01/01/11 to 12/31/11
Outputs
OUTPUTS: Progress in 2011: 1. Established a corn earworm Cry1Ac-resistant strain (Named GAR1) by laboratory selection of field populations collected from Georgia; 2. Bioassays of corn earworm field populations from Georgia showed that many populations had 20-40 fold resistance to Cry1Ac relative to our susceptible strain; 3. Cloned cadherin, APN, Alkaline phosphatase and five proteases from the Cry1Ac susceptible Benson strain and Cry1Ac-resistant GAR1 strain; 4. Sequence analyses of these genes allow us to identify consistent point mutations between resistant and susceptible alleles of cadherin and APN genes; 5. Transposon display shows that Hztransib has been active in the corn earworm laboratory and field populations; 6. Identification of flavone and xanthotoxin-responsive elements from corn earworm P450 gene CYP321A1; 7. Tested the efficacy of edible oils on ear pests of sweet corn; 8. Confirmed foliage resistance to fall armyworm in corn germplasm lines that confer resistance to root- and ear-feeding insects. Dissemination: Some of the results obtained are published in scientific journals; others are presented at professional meetings or Universities in USA and China. PARTICIPANTS: Min Zhang, Andrew Wong, Qingli Shang. TARGET AUDIENCES: Corn growers, people working on ecology and management of corn pests, and people working on transposable elements and gene regulation. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
1. Cry1Ac resistance in corn earworm is most likely due to point mutations in cadherin and APN genes; 2. The transposable element Hztransib and its host corn earworm have co-evolved a regulatory mechanism to silence Hztransib in normal conditions and reactivate it upon uncharacterized stress; 3. The essential flavone-responsive element (called XRE-Fla) also regulate xanthotoxin induction of the corn earworm P450 gene CYP321A1.
Publications
- 1. Ni, X., A. N. Sparks, Jr., D. G. Riley, and X. Li. 2011. Impact of edible oils on ear pests of sweet corn. Journal of Economic Entomology 104: 956-964 (doi: 10.1603/EC10356).
- 2. Ni, X., Chen, Y., Hibbrad, B., Wilson, J., Williams, W., Buntin, G. D., Ruberson, J., and X. Li. 2011. Foliage resistance to fall armyworm in corn germplasm lines that confer resistance to root- and ear-feeding insects. Florida Entomologist 94(4): 971-981.
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Progress 01/01/10 to 12/31/10
Outputs
OUTPUTS: Progress made in this year: 1. We have continuously selected our Cry1Ac-resistant strain. 2. We have obtained the full-length sequence of the Bt target genes cadherin and APN from from both the susceptible and Cry1AC-resistant strain. No major indels have been found between the resistant and susceptible alleles. 3. We have characterized the essential cis-acting element for flavone induction of H. zea P450 gene CYP321A1; 4. We have confirmed that Hztransib is functiona active. DISSEMINATION: Some of results have been published or in press. Some of results were presented in various meetings or seminars. PARTICIPANTS: 1. Chonglie Ma, Research Scientist. 2. Chunni Zhang, PhD student. 3. Erxia Du, PhD student 4. Min Zhang, PhD student. 5. Andy Wong, Research Technician. 6 Qingli Shang, Postdoc. TARGET AUDIENCES: People work on Pest Management, Plant-Insect interactions, Gene Regulation, and Transposons. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
1. Cloning of the corn earworm cadherin, APN, and trpsin genes is an important step for understanding the genetic and molecular mechanisms of corn earworm to Bt-transgenic crops; 2. Characterization plant allelechemical-responsible cis elements and transcriptionfactors will not only promote our understanding of signaling interactions between plants and insects, but will also provide new avenues for insecticide development and pest control; 3. The identification of corn earworm genes for RNAi-based control of corn earworm may be used to produce the next generation of transgenic crops for controlling Bt-resistant lepidopteran pests and non-lepidopteran pests.
Publications
- Zhang, C., Luo, X., Ni, X., Zhang, Y. and Li, X. 2010. Functional characterization of cis-acting elements mediating flavone-inducible expression of CYP321A1. Insect Biochemistry and Molecular Biology. doi:10.1016/j.ibmb.2010.09.003
- Du, E., Ni, X., Zhao, H. and Li, X. 2010. Natural history and intragenomic dynamics of the Transib transposon Hztransib in the cotton bollworm Helicoverpa zea. Insect Molecular Biology (in press)
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Progress 01/01/09 to 12/31/09
Outputs
OUTPUTS: Progress made in this year: 1. We have generated a laboratory resistant strain with approximately 150-fold resistance to Cry1Ac by laboratory selection. Selection is still ongoing to further increase resistance; 2. We have tested resistance of several corn earworm field populations collected from Georgia in 2009 to Cry1Ac and Cry2Ab by diet incorporation and/or leaf bioassays; 3. We have obtained the full-length sequence of the Bt target gene cadherin from the susceptible strain; 4. We have confirmed that the transposon insertion previously found in the resistant populations didn't disrupt the splicing of cadherin mRNA; 5 We have cloned partial sequence Bt toxin target gene APN by degerate RTPCR; 6. We have cloned partial sequences of several trpsin genes; We have cloned partial sequence the candidate positive regulator for flavone induction of CYP321A1; 7. We have produced over 20 Arabidopsis lines that express double-strand RNA of corn earworm genes; several of these lines killed over 85% of corn earworm larvae; 8. We have examined the natural history and intragenomic dynamics of Hztransib in H. zea by PCR and DNA transposon Display. DISSEMINATION: Some of the results have been submitted to journals and are currently under review. Some of the results were presented in various meetings or seminars. PARTICIPANTS: 1. Chonglie Ma, Research Scientist. 2. Chunni Zhang, PhD student. 3. Erxia Du, PhD student 4. Min Zhang, PhD student. 5. Andy Wong, Research Technician TARGET AUDIENCES: People working on Pest Management, Plant-Insect interactions, Gene Regulation, and Transposons. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
1. Cloning of the corn earworm cadherin, APN, and trpsin genes is an important step for understanding the genetic and molecular mechanisms of corn earworm to Bt-transgenic crops; 2. Characterization plant allelechemical-responsible cis elements and transcription factors will not only promote our understanding of signaling interactions between plants and insects, but will also provide new avenues for insecticide development and pest control; 3. The identification of corn earworm genes for RNAi-based control of corn earworm may be used to produce the next generation of transgenic crops for controlling Bt-resistant lepidopteran pests and non-lepidopteran pests.
Publications
- Li, X. & Ni, X. 2009. Deciphering the plant-insect phenotypic arms race. In Recent Advances in Entomological Research: From Molecular Biology to Pest Management, Liu, T-X. and Kang, L. (eds.), Higher Education Press, Beijing, China (in press).
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: Progress made in this year: 1. Continue to select resistance of the corn earworm to Bt toxin Cry1Ac and Cry2Ab in the lab(ongoing); 2. We have tested resistance of several corn earworm field populations collected from Georgia in 2008 to Cry1Ac and Cry2Ab by diet incorporation and/or leaf bioassays; 3. We have cloned and compared the partial sequence of the Bt target gene cadherin between resistant populations and our susceptible lab strain. A transposon-like insertion that disrupts the splicing of cadherin mRNA has been found in the resistant populations but not in the susceptible lab strain; 4. We have idetified the basal, xanthotoxin-, and flavone-responsible cis-elements for regualtion of CYP321A1 expression by testing the promoter activities of those constructs; 5. We have fully characterized the first intact Transib transposon from the corn earworm; and 6. We have conducted a transposon display to estimate the duplication and transposion activity of Hztransib in several corn earworm lab strains. DISSEMINATION: Some of results have been published and we are currently writing several manuscripts. Some of results were presented in various meetings or seminars. PARTICIPANTS: 1. Song Chen, postdoc. 2. Chunni Zhang, PhD student 3. Erxia Du, PhD student 4. Min Zhang, PhD student. TARGET AUDIENCES: People work on Pest Management, Plant-Insect interactions, Gene Regulation, and Transposons. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
1. Partial cloning of the corn earworm cadherin gene is an important step for understanding the genetic and molecular mechanisms of corn earworm to Bt-transgenic crops; 2 Identification of a cadherin transposon insertion allele from the resistant populations will provide a powerful DNA marker for monitoring corn earworm resistance to Bt crops and studying Bt resistance in this pest; 3. Characterization plant allelechemical-responsible cis elements will not only promote our understanding of signaling interactions between plants and insects, but will also provide new avenues for insecticide development and pest control; 4. The characterized first intact Transib element Hztransib from the corn earworm can be used as a model element to dissect the transposition mechanism of Transib transposons; and 5. Hztranisb can be developed as a novel DNA vector that targets on GC-rich sequence. The current widely used vectors target on TA-rich sequence.
Publications
- Chen, S. and Li, X. 2008. Molecular characterization of the first intact Transib transposon from Helicoverpa zea. Gene 408:51-63.
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Progress 01/01/07 to 12/31/07
Outputs
Progress made in this year: 1. Select resistance of the corn earworm to Bt toxin Cry1Ac in the lab(ongoing). 2. Compared the toxicities of Cry1Ac, Cry 1Ab, modified Cry1Ac, and modified Cry1Ab to the corn earworm. 3. Tested the allelochemical inducibility of the corn earworm cytochrome P450 CYP321A2 and CYP321A1 by qRTPCR; 4. Found twelve novel transposons inserted in six allelochemical-metabolizing corn earworm P450 genes (CYP6B8, CYP6B27, CYP321A1, CYP321A2, CYP9A12v3, and CYP9A14). 5. Characterized the first intact Transib transposon (named Hztransib) from corn earworm.
Impacts
1. The Cry1Ac resistant strain currently under lab selection can be used for studying cross resistance and resistance mechanisms 2. Identification of twelve novel transposons in six xenobiotic-metabolizing H. zea P450 genes present for the first time evidence that transposons are selectively retained within or in close proximity to xenobiotic-metabolizing P450 genes. 3. Characterization of Hztransib, the first intact and active Transib transposons found in any organisms, has at least two important impacts. First, It can be used as a model element to dissect the transposition mechanism of Transib transposons. Second, it can be developed as a novel DNA vector that targets on GC-rich sequence. The current widely used vectors target on TA-rich sequence.
Publications
- Song Chen and Xianchun Li. 2007. Transposable elements are enriched within or in close proximity to xenobiotic-metabolizing cytochrome P450 genes. BMC Evolutionary Biology 2007, 4:46
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