Progress 07/01/08 to 06/30/13
Outputs
Progress Report Objectives (from AD-416): The objective of this research is to increase understanding of the molecular basis of host resistance and insect virulence in the wheat/ Hessian fly system. The long-term goal is to develop strategies for durable resistance to this important insect pest. Approach (from AD-416): The molecular basis of host resistance will be approached by cloning and characterizing a wheat resistance gene for Hessian fly known as Hdic from Triticum turgidum subsp. dicoccum. This resistance gene resides in a region of wheat chromosome 1A that contains at least 14 other resistance genes for Hessian fly. Candidate genes will be identified by fine mapping and sequencing of BAC contigs. Candidate genes will be tested initially by gene silencing using RNA interference. A cosmid library from the donor of Hdic will be constructed to isolate the resistance allele. Expression vectors will be constructed for the candidate gene and tested for ability to confer resistance to Hessian fly. The molecular basis of Hessian fly virulence/avirulence will be approached by determining the functions of secreted salivary gland proteins (SSGP) of Hessian fly in virulence or avirulence to wheat. Differential gene expression of SSGPs will be tested in different biotypes of Hessian fly using a custom-designed microarray. Candidate genes for virulence or avirulence effectors will be identified. Candidate genes will be tested by gene silencing using RNA interference. Hessian fly is a major insect pest of wheat. The insect is mainly controlled through host plant resistance. Therefore, understanding the mechanisms of wheat defense against Hessian fly may provide useful information to improve wheat resistance to Hessian fly. One potential target for plant defense against insects is the digestive enzymes, particularly proteases, in the insect gut. This research took advantage of the availability of the Hessian fly genome sequence and systematically analyzed the composition and expression of all digestive proteases in the Hessian fly larval gut. Major putative digestive trypsins, chymotrypsins, and cysteine proteases were identified and their expression profiles among tissues and different developmental stages were determined. The study should provide a foundation for future research for utilization of plant protease inhibitors for management of this insect pest. Plant parasites, including many insects, manipulate plants in order to utilize the host resources. Here, we show that the Mayetiola destructor susceptibility gene-1 (Mds-1) of wheat encodes a small heat-shock protein and is a major susceptibility gene for infestation of wheat by the gall midge M. destructor, commonly known as the Hessian fly. Transcription of Mds-1 increased upon insect infestation. Silencing of Mds-1 transcript levels by RNA interference conferred immunity to all Hessian fly biotypes on normally susceptible wheat genotypes. Over-expression or induction by heat shock of Mds-1 suppressed resistance mediated by the resistance gene H13. Mds-1-silenced plants were also found to be resistant to the powdery mildew fungus, and Mds-1 expression was up-regulated during the fungal infection of normal wheat plants, suggesting that Hessian fly and powdery mildew exploit a common stress response pathway for parasitism. Modification of susceptibility genes may provide a potentially broad and durable source of resistance to Hessian fly and powdery mildew.
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Progress 10/01/11 to 09/30/12
Outputs
Progress Report Objectives (from AD-416): The objective of this research is to increase understanding of the molecular basis of host resistance and insect virulence in the wheat/Hessian fly system. The long-term goal is to develop strategies for durable resistance to this important insect pest. Approach (from AD-416): The molecular basis of host resistance will be approached by cloning and characterizing a wheat resistance gene for Hessian fly known as Hdic from Triticum turgidum subsp. dicoccum. This resistance gene resides in a region of wheat chromosome 1A that contains at least 14 other resistance genes for Hessian fly. Candidate genes will be identified by fine mapping and sequencing of BAC contigs. Candidate genes will be tested initially by gene silencing using RNA interference. A cosmid library from the donor of Hdic will be constructed to isolate the resistance allele. Expression vectors will be constructed for the candidate gene and tested for ability to confer resistance to Hessian fly. The molecular basis of Hessian fly virulence/avirulence will be approached by determining the functions of secreted salivary gland proteins (SSGP) of Hessian fly in virulence or avirulence to wheat. Differential gene expression of SSGPs will be tested in different biotypes of Hessian fly using a custom-designed microarray. Candidate genes for virulence or avirulence effectors will be identified. Candidate genes will be tested by gene silencing using RNA interference. Hessian fly is mainly controlled through host plant resistance. Therefore, understanding the mechanisms of wheat defense may provide useful information to improve wheat resistance to Hessian fly. One potential target for plant defense against insects is the digestive enzymes, particularly proteases, in the insect gut. This research took advantage of the availability of the Hessian fly genome sequence and systematically analyzed the composition and expression of all digestive proteases in the Hessian fly larval gut. Major putative digestive trypsins, chymotrypsins, and cysteine proteases were identified and their expression profiles among tissues and different developmental stages were determined. This work should provide a foundation for future research for utilization of plant protease inhibitors for management of this insect pest. One of the promising new means for insect control is based on small, non- coding RNA molecules known as small interfering RNAs (siRNAs) and microRNAs (miRNAs). Small RNAs can silence insect genes, resulting in the death of the insect. This work identified and characterized a large number of miRNAs for the first time in Hessian fly. Some of the miRNAs were found to be Hessian fly-specific and their expression was affected by host plant genotypes. Further research will be directed toward testing different delivery methods so that miRNAs can be tested for ability to control this insect pest.
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Progress 10/01/10 to 09/30/11
Outputs
Progress Report Objectives (from AD-416) The objective of this research is to increase understanding of the molecular basis of host resistance and insect virulence in the wheat/Hessian fly system. The long-term goal is to develop strategies for durable resistance to this important insect pest. Approach (from AD-416) The molecular basis of host resistance will be approached by cloning and characterizing a wheat resistance gene for Hessian fly known as Hdic from Triticum turgidum subsp. dicoccum. This resistance gene resides in a region of wheat chromosome 1A that contains at least 14 other resistance genes for Hessian fly. Candidate genes will be identified by fine mapping and sequencing of BAC contigs. Candidate genes will be tested initially by gene silencing using RNA interference. A cosmid library from the donor of Hdic will be constructed to isolate the resistance allele. Expression vectors will be constructed for the candidate gene and tested for ability to confer resistance to Hessian fly. The molecular basis of Hessian fly virulence/avirulence will be approached by determining the functions of secreted salivary gland proteins (SSGP) of Hessian fly in virulence or avirulence to wheat. Differential gene expression of SSGPs will be tested in different biotypes of Hessian fly using a custom-designed microarray. Candidate genes for virulence or avirulence effectors will be identified. Candidate genes will be tested by gene silencing using RNA interference. We have cloned and characterized the Hessian fly resistance gene Hdic from wheat. Interestingly, the gene has homology to typical disease resistance genes. A manuscript is in preparation. We analyzed bacteria associated with Hessian fly at different developmental stages. Diverse bacteria were found in Hessian fly larvae, pupae, and adults. Most of the bacteria were transferred to the next generation through eggs. Removal of bacteria from the insect through antibiotics resulted in high mortality of Hessian fly larvae, indicating that symbiotic bacteria were essential for the insect to survive on wheat seedlings. Similar bacteria were also found in Hessian fly-infested wheat, suggesting that Hessian fly larvae transmit bacteria into plant tissue, and that these transmitted bacteria may play a role in the wheat- Hessian fly interaction. This research provides a foundation for future research on the role of bacteria in Hessian fly biology and virulence. Phytohormones were investigated for their possible role in parasitism of the Hessian fly on wheat. Salicylic acid and 12-oxo-phytodienoic acid were increased in both a resistant wheat variety and rice, which is a non- host. This suggests that phytohormones may be important components of the defense response. This research provides a foundation for future work on the role of phytohormones and fatty acids in the defense response against Hessian fly. Small interfering RNA (siRNA) has recently been found to play an important role in gene expression in eukaryotic organisms. Work was initiated on siRNA species in Hessian fly, and their potential roles in wheat/Hessian fly interactions. Progress on this agreement is monitored by regularly discussing program goals, approaches, and results (teleconference, email) and by reviewing annual accomplishments reports.
Impacts
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Progress 10/01/09 to 09/30/10
Outputs
Progress Report Objectives (from AD-416) The objective of this research is to increase understanding of the molecular basis of host resistance and insect virulence in the wheat/Hessian fly system. The long-term goal is to develop strategies for durable resistance to this important insect pest. Approach (from AD-416) The molecular basis of host resistance will be approached by cloning and characterizing a wheat resistance gene for Hessian fly known as Hdic from Triticum turgidum subsp. dicoccum. This resistance gene resides in a region of wheat chromosome 1A that contains at least 14 other resistance genes for Hessian fly. Candidate genes will be identified by fine mapping and sequencing of BAC contigs. Candidate genes will be tested initially by gene silencing using RNA interference. A cosmid library from the donor of Hdic will be constructed to isolate the resistance allele. Expression vectors will be constructed for the candidate gene and tested for ability to confer resistance to Hessian fly. The molecular basis of Hessian fly virulence/avirulence will be approached by determining the functions of secreted salivary gland proteins (SSGP) of Hessian fly in virulence or avirulence to wheat. Differential gene expression of SSGPs will be tested in different biotypes of Hessian fly using a custom-designed microarray. Candidate genes for virulence or avirulence effectors will be identified. Candidate genes will be tested by gene silencing using RNA interference. The objective of this research is to increase understanding of the molecular basis of host resistance and insect virulence in the wheat/Hessian fly system. Progress continued on the effort to clone the wheat resistance gene Hdic, which confers resistance to Hessian fly. Candidate genes have been identified and are being tested. We discovered a rapid mobilization of membrane lipids in resistant plants in response to Hessian fly attack. Mobilized lipids are likely converted into defense signaling molecules and components for cell wax. This discovery suggests that lipid mobilization and conversion might be a necessary molecular basis for plants to be resistant to Hessian fly. This work is among the first studies for systematic analysis of membrane lipids in plant defense. Progress on this agreement is monitored by regularly discussing program goals, approaches, and results (teleconference, email) and by reviewing annual accomplishments reports.
Impacts
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Progress 10/01/08 to 09/30/09
Outputs
Progress Report Objectives (from AD-416) The objective of this research is to increase understanding of the molecular basis of host resistance and insect virulence in the wheat/Hessian fly system. The long-term goal is to develop strategies for durable resistance to this important insect pest. Approach (from AD-416) The molecular basis of host resistance will be approached by cloning and characterizing a wheat resistance gene for Hessian fly known as Hdic from Triticum turgidum subsp. dicoccum. This resistance gene resides in a region of wheat chromosome 1A that contains at least 14 other resistance genes for Hessian fly. Candidate genes will be identified by fine mapping and sequencing of BAC contigs. Candidate genes will be tested initially by gene silencing using RNA interference. A cosmid library from the donor of Hdic will be constructed to isolate the resistance allele. Expression vectors will be constructed for the candidate gene and tested for ability to confer resistance to Hessian fly. The molecular basis of Hessian fly virulence/avirulence will be approached by determining the functions of secreted salivary gland proteins (SSGP) of Hessian fly in virulence or avirulence to wheat. Differential gene expression of SSGPs will be tested in different biotypes of Hessian fly using a custom-designed microarray. Candidate genes for virulence or avirulence effectors will be identified. Candidate genes will be tested by gene silencing using RNA interference. Significant Activities that Support Special Target Populations The objective of this research is to increase understanding of the molecular basis of host resistance and insect virulence in the wheat/Hessian fly system. The long-term goal is to develop strategies for durable resistance to this important insect pest. The most significant accomplishment of the past year was the finding that reactive oxygen species (ROS) are part of plant defense against Hessian fly larval attack. This finding is important because in the literature, a previous report indicated that NADPH-dependent oxidases are not involved in wheat defense against Hessian fly larval attack. Since NADPH-dependent oxidases are key enzymes responsible for generation of ROS in many plant-pathogen systems, the lack of involvement of NADPH-oxidase in the wheat-Hessian fly interaction suggested that ROS are not part of wheat defense against Hessian fly. We discovered a high level of ROS, particularly hydrogen peroxide, accumulated in plants during resistant interactions, but no change in ROS in plants during susceptible interactions. This information increases our understanding of resistance and susceptibility in this insect-plant system. Progress on this agreement is monitored by regularly discussing program goals, approaches, and results (teleconference, email) and by reviewing annual accomplishments reports.
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Progress 10/01/07 to 09/30/08
Outputs
Progress Report Objectives (from AD-416) The objective of this research is to increase understanding of the molecular basis of host resistance and insect virulence in the wheat/Hessian fly system. The long-term goal is to develop strategies for durable resistance to this important insect pest. Approach (from AD-416) The molecular basis of host resistance will be approached by cloning and characterizing a wheat resistance gene for Hessian fly known as Hdic from Triticum turgidum subsp. dicoccum. This resistance gene resides in a region of wheat chromosome 1A that contains at least 14 other resistance genes for Hessian fly. Candidate genes will be identified by fine mapping and sequencing of BAC contigs. Candidate genes will be tested initially by gene silencing using RNA interference. A cosmid library from the donor of Hdic will be constructed to isolate the resistance allele. Expression vectors will be constructed for the candidate gene and tested for ability to confer resistance to Hessian fly. The molecular basis of Hessian fly virulence/avirulence will be approached by determining the functions of secreted salivary gland proteins (SSGP) of Hessian fly in virulence or avirulence to wheat. Differential gene expression of SSGPs will be tested in different biotypes of Hessian fly using a custom-designed microarray. Candidate genes for virulence or avirulence effectors will be identified. Candidate genes will be tested by gene silencing using RNA interference. Significant Activities that Support Special Target Populations This is a new cooperative project on Hessian fly resistance in wheat that began 7/01/2008. Experiments have been initiated to clone and characterize a wheat resistance gene for Hessian fly known as Hdic from Triticum turgidum subsp. dicoccum. This resistance gene resides in a region of wheat chromosome 1A that contains at least 14 other resistance genes for Hessian fly. Information on this gene cluster may be valuable for developing strategies for more durable resistance to Hessian fly. Progress on this agreement is monitored by regularly discussing program goals, approaches, and results (teleconference, email) and by reviewing annual accomplishments reports.
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