Location: Molecular Plant Pathology Laboratory2014 Annual Report
The goal of this project is to devise, develop, and implement novel, advanced biotechnologies to improve pest and disease resistance in sugar beet that will lead to an improvement in yield and sugar production. Molecular understanding of how plants protect themselves from insect attack and the complementary insect responses to interactions with host plants will be deciphered. Specific objectives are: 1) identify and characterize genes associated with enhanced tolerance to the sugar beet root maggot with focus on the sugar beet taproot; 2) define sugar beet gene promoters for targeting beneficial gene expression to taproot tissues most prone to pest and pathogen attack; and 3) characterize and improve screening of sugar beet for resistance to the sugar beet root maggot by identifying sugar beet root maggot genes that are essential in resistant and susceptible interactions with the host plant.
Sugar beet root defense genes incited by the root maggot, a destructive pest of sugar beet, will be characterized using molecular approaches to facilitate screening of sugar beet germplasm for resistance and to devise novel strategies for pest and disease control. Root genes identified as being important in plant defense will be expressed in susceptible plants and screened for enhanced levels of insect pest and phytopathogen resistance. Two resistance genes that preferentially respond to maggot feeding in a moderately resistant germplasm will be studied. One of these genes codes for a serine proteinase inhibitor (PI; BvSTI), and the other for a cell wall polygalacturonase inhibitor (PGIP, BvPGIP). BvSTI is a wound-inducible Kunitz trypsin PI with specificity for the root maggot digestive enzymes that mediate release of essential nutrients from ingested plant tissues. The second gene, BvPGIP, codes for a leucine-rich repeat glycoprotein PGIP associated with cell wall structure and plant defense responses. The role of the sugar beet BvSTI and BvPGIP genes in mediating resistance will be determined by transferring the recombinant genes into sugar beet hairy roots and model whole plants (Nicotiana and Arabidopsis). Genetically modified plants will be bioassayed for resistance to insect pests and phytopathogens. Insect bioassays will include fall armyworm, beet armyworm, or tobacco hornworm larvae and phytopathogens Aphanomyces cochlioides and Fusarium oxysporum that cause root rot in sugar beet. To more precisely target the expression of resistance genes to root cells and tissues most prone to pest and pathogen attack, root tissue-specific and temporal promoters will be identified, cloned, and functionally characterized by differential screening of sugar beet root EST libraries. Cloned promoters will be fused with a reporter gene (GUS) in a plant transformation vector and introduced into sugar beet hairy roots and model whole plants. Various biotic and abiotic stresses such as infestation with insect pests, infection with phytopathogens, mechanical wounding, and treatment with defense response elicitors such as methyl jasmonate and salicylic acid will be used to localize GUS gene expression driven by the selected sugar beet promoters. In complementary studies of insect responses, root maggot genes that are important in resistant and susceptible interactions with the sugar beet root will be identified. Root maggot genes will be profiled, sequenced, and functionally annotated to gain new knowledge of how insects adapt to host plants and surmount host resistance. Expression patterns of identified root maggot genes will be examined to confirm that the selected insect genes are specificity-expressed as a response to feeding on the sugar beet root.
Delivering a safe and secure supply of food to a rising global population, while minimizing harmful impacts on cropping ecosystems, will require that the world’s major crops have increased capacity to resist diseases and insect pests. Sugar beet is an economically important plant that is attacked by numerous insects and pathogens that damage the plant and reduce sugar yields. To improve resistance to insect pests and microbial pathogens, novel resistance traits need to be introduced to sugar beet. A sugar beet gene was identified that is involved in the assembly of the outer protective layer (cell wall) of the root. This outer layer of the plant serves as a barrier and first line of defense against invading insect pests and microbial pathogens. This cell wall gene was cloned and rebuilt for further analysis of its role in plant defense capabilities. The newly gained knowledge will be used to develop plants with stronger outer protective barriers that will improve pest and disease resistance in economically important plants. To effectively steer the production of insecticidal compounds to plant parts most prone to insect attack, characterization of regulatory switches (plant promoters) is needed. Several interesting sugar beet switches were identified that have the capability of directing insect and pathogen fighting compounds to the root surfaces, the root itself or to the leaves. This information will be used to develop safer approaches of insect control in plants and lead to increased yields and reduced usage of chemical pesticides. Sugar beet root maggot is a destructive pest of sugar beet that is not easily controlled without the use of harmful chemical pesticides. To identify root maggot genes that are important in the interaction of the insect with the resistant and susceptible sugar beet roots, a library of root maggot genes was prepared. These root maggot response genes will be sequenced and functionally annotated to gain new knowledge of how insects adapt to host plants and surmount host resistance.
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