Beta vulgaris L. serine proteinase inhibitor gene expression in insect resistant sugar beet

Expression pattern of a sugar beet serine proteinase inhibitor gene, BvSTI, was characterized in response to mechanical and fall armyworm (FAW; Spodoptera frugiperda J.E. Smith) induced wounding. BvSTI expression was analyzed in three breeding lines moderately resistant to sugar beet root maggot (Tetanops myopaeformis Roder) and in a susceptible line, F1010. Increased mechanical wound induced levels of BvSTI expression were observed in all resistant lines as compared to F1010 during the first 24 h. The most intensive response to wounding was observed in one of the resistant lines, F1016, with a maximum 5- and 2.5-fold increase of BvSTI transcript levels over non-wounded roots and leaves, respectively. In contrast, slight increase of BvSTI transcript levels in leaves and even an initial decrease in roots were observed in F1010. BvSTI transcript accumulation in F1016 and F1010 tissues wounded by FAW showed a similar gene expression pattern, but it was delayed and less intense than the response incited by abiotic wounding. On the protein level, BvSTI specific antibody confirmed increased accumulation of the 30 kDa BvSTI protein in wounded leaves but not in roots of F1016 and F1010. Using trypsin inhibition assays, the activity of BvSTI was confirmed in F1016 roots and leaves and F1010 leaves. In F1010 roots BvSTI activity was completely lacking. We conclude that BvSTI gene expression was wound induced in the insect resistant germplasm suggesting that BvSTI can be used in biotechnological approaches or in breeding programs for improving insect resistance.