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Title: Insect resistance to sugar beet pests mediated by a Beta vulgaris proteinase inhibitor transgene

Author
item Smigocki, Anna
item IVIC-HAYMES, SNEZANA - TOWSON UNIV, TOWSON, MD
item ZUZGA, SABINA - WARSAW, POLAND
item SAVIC, JELENA - BELGRADE, SERBIA

Submitted to: American Society of Sugarbeet Technologists
Publication Type: Proceedings
Publication Acceptance Date: 7/27/2010
Publication Date: 7/27/2010
Citation: Smigocki, A.C., Ivic-Haymes, S.D., Zuzga, S., Savic, J. Insect resistance to sugar beet pests mediated by a Beta vulgaris proteinase inhibitor transgene. Proceedings of the American American Society of Sugarbeet Technologists 35th General Meeting, ASSBT, Denver, CO.

Interpretive Summary: Disease and pest problems are responsible for decreases in production of sugar from sugar beet. Over 26 million tons of sugar beet valued at over 1.2 billion dollars are produced each year in the U.S. To gain a better understanding of how plants protect themselves from insect attack, in our past studies we identified sugar beet genes that respond to sugar beet root maggot infestation in root maggot-susceptible and moderately resistant sugar beet varieties. One of the genes (BvSTI) was selected for further analysis to assess its effectiveness in controlling insect pests of sugar beet. In this study, we report new findings on production of a model plant (Nicotiana benthamiana) and a model sugar beet root system that are genetically modified to overproduce the sugar beet gene (BvSTI) product. Our results indicate that when beet armyworm, fall armyworm and tobacco hornworm insects feed on these plants they have a higher mortality rate than ones that feed on unmodified plants. Of the insects that survive, their size and weight is reduced in comparison to insects that feed on the unmodified plants. These results suggest that the BvSTI sugar beet gene contributes to insect resistance and may be useful for control of insect damage in plants other than sugar beet. Scientists will use this information to identify components of plant resistance mechanisms that will lead to new approaches for increasing pest and disease resistance in plants.

Technical Abstract: We transformed sugar beet (Beta vulgaris) hairy roots and Nicotiana benthamiana plants with a Beta vulgaris root gene (BvSTI) that codes for a serine proteinase inhibitor. BvSTI is a root gene cloned from the F1016 breeding line that has moderate levels of resistance to the sugar beet root maggot (Tetanops myopaeformis), a major pest of sugar beet. Root maggot damage deforms roots and predisposes them to other pests and pathogens that reduce yield and quality. Transformants had high levels of BvSTI or GUS gene expression driven by the constitutive 35S or the BvSTI gene specific promoter, respectively. Polyacrylamide gel electrophoresis zymograms revealed clear zones that corresponded to proteinase inhibitor (PI) activities at ~24, 26 and 28 kDa in the sugar beet BvSTI transformants and 26 and 28 kDa in the N. benthamiana plants. Several insect pests of sugar beet and tobacco were bioassayed for resistance on the BvSTI-transgenic plant materials. Spodoptera frugiperda (fall armyworm), Spodoptera exigua (beet armyworm) and Manduca sexta (tobacco hornworm) larvae that were fed tobacco leaves or sugar beet roots that express the BvSTI gene exhibited higher mortality rates or were delayed in growth and development relative to control larvae. Since serine proteases comprise the major digestive enzymes in root maggot midguts, our findings suggest that the BvSTI gene is likely involved in root maggot resistance mechanisms in the F1016 genotype.