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Title: A Beta vulgaris serine proteinase inhibitor gene (BvSTI) regulated by sugar beet root maggot feeding on moderately resistant F1016 roots.

Author
item Smigocki, Anna
item PUTHOFF, D - MPPL
item IVIC-HAYMES, S - TOWSON UNIV TOWSON MD
item ZUZGA, S - WARSAW POLAND

Submitted to: American Society of Sugarbeet Technologists
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/9/2007
Publication Date: 7/13/2007
Citation: Smigocki, A.C., Puthoff, D.P., Ivic-Haymes, S.D., Zuzga, S. 2007. A beta vulgaris serine proteinase inhibitor gene (bvsti) regulated by sugar beet root maggot feeding on moderately resistant f1016 roots. American Society of Sugarbeet Technologists Proceedings. 34:143-150.

Interpretive Summary: Disease and pest problems are responsible for decreases in production of sugar from sugar beet. One of the most devastating insect pests of sugar beet is the sugar beet root maggot that is currently found in more than half of all U.S. sugar beet fields. Chemical insecticides are the only available measure for control of the maggot and a strong drive exists for development of alternative, environmentally friendly control measures. To gain a better understanding of how plants protect themselves from insect attack, we identified sugar beet genes that respond to sugar beet root maggot infestation in either root maggot-susceptible or moderately resistant sugar beet varieties. Based on molecular characterization, one gene in particular was selected for further analysis of its role in root maggot resistance. Overproduction of the gene in a laboratory model of a sugar beet root system is being utilized to assess this gene's function in insect resistance. This information will be used by scientists to increase our knowledge of plant insect resistance mechanisms and lead to environmentally safer approaches of insect control by reducing the use of harmful pesticides.

Technical Abstract: Damage from the sugar beet root maggot (SBRM) is a serious problem and control of this devastating pest ultimately relies on environmentally damaging insecticides. To explore novel strategies for management of SBRM and gain knowledge of root defense response mechanisms, we examined root gene expression incited by SBRM in a moderately resistant F1016 and a susceptible parental F1010 line. A gene of particular interest, coding for a serine (trypsin) protease inhibitor (BvSTI), was identified in the F1016 EST library. BvSTI shares sequence similarity with a tomato gene that is primarily expressed in the maturing epidermis of the root, is induced by invading nematodes, and is secreted to the rhizosphere. Since serine proteases comprise the major digestive enzymes in root maggot midguts, our findings suggest that BvSTI may be involved in the resistance mechanism of F1016. To elucidate the functional role of BvSTI , its coding region was fused to the CaMV 35S promoter for over-expression in sugar beet hairy root cultures. Trypsin inhibitory activity increased 2 to 4-fold in the transformed roots. Studies on the effects of the inhibitor on insect mortality and growth rates are in progress. Cloning of BvSTI suggests that the proteinase inhibitor may form a zone of protection surrounding the moderately resistant F1016 roots and act as a first line of defense in the peripheral cell layers.