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Submitted to: Annual Beet Sugar Development Foundation Research Report
Publication Type: Other Publication Acceptance Date: 1/1/2006 Publication Date: 1/1/2006 Citation: Smigocki, A.C. 2006. Cloning of beta vulgaris root ests modulated by sugar beet root maggot feeding: role of proteinase inhibitors in insect resistance. Annual Beet Sugar Development Foundation Research Report. Res. E2-6. Interpretive Summary: Damage from sugar beet root maggot is a serious problem in the north-central and western United States and Canada. More than two-thirds of the l.5 million sugar beet-producing acres in the United States are infested with the root maggot. A handful of chemical insecticides have been in use for over 30 years, and recent concerns about pesticide safety and potential for resistance development have serious implications for the profitability of sugar beet production in the future. Alternative methods of control need to be identified and pursued since germplasm with complete resistance to the maggot is not available. We identified sugar beet traits (genes) that are associated with root responses to root maggot feeding in both susceptible and moderately resistant sugar beet varieties. One of the genes is specifically associated with resistance and targets the major digestive enzymes in root maggot stomachs. To functionally characterize the role of this gene in mediating resistance to the root maggot, we used biotechnological approaches to overproduce the gene in sugar beet roots. Scientists will use this information to identify plant resistance mechanisms that will lead to new approaches for increasing resistance to root maggot in economically important sugar beet varieties without the use of harmful pesticides. Technical Abstract: Damage from sugar beet root maggot, Tetanops myopaeformis von Röder (SBRM), is a serious problem in the north-central and -western United States and Canada. More than two-thirds of the l.5 million sugar beet-producing acres in the United States are infested with SBRM. A handful of chemical insecticides have been in use for over 30 years, and recent concerns with regards to pesticide safety and potential for resistance development have serious implications for the profitability of sugar beet production in the future. Alternative methods of control need to be identified and pursued since germplasm with complete resistance to SBRM is not available. We recently identified sugar beet root ESTs that are modulated by SBRM feeding in both a moderately resistant (F1016) and a susceptible parental (F1010) line. One of the genes, BvSTI, is specifically up-regulated in the moderately resistant F1016 germplasm by SBRM infestations. BvSTI encodes a protein with a conserved motif denoting it a member of the Kunitz trypsin (serine) proteinase inhibitor family. BvSTI also shares similarity with a tomato gene that is primarily expressed in the root, secreted to the rhizosphere and induced by nematodes. Since we showed that serine and aspartyl proteases comprise the major digestive enzymes in root maggot midguts, our findings suggest that BvSTI may form a zone of protection surrounding the moderately resistant roots and act as a first line of defense in the peripheral cell layers. To functionally characterize the role of BvSTI in mediating resistance to SBRM, we cloned the full length coding sequence of BvSTI and over-expressed it in sugar beet hairy roots. |
