Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Recent advances in functional genomics for sugar beet (Beta vulgaris L.) improvement: progress in determining the role of BvSTI in pest resistance in roots.

Abstract

We recently reported root-specific gene expression incited by sugarbeet root maggot (SBRM; Tetanops myopaeformis) feeding on moderately resistant (F1016) and susceptible (parental F1010 line) sugarcane genotypes. A cDNA expressed sequence tag (EST) coding for a serine (trypsin-type) protease [proteinase] inhibitor (BvSTI) was identified. BvSTI shared sequence similarity with a root-specific tomato gene whose expression was induced by insect feeding. Since serine proteases comprise the major digestive enzymes in root maggot midguts, we hypothesized that BvSTI may be involved in resistance. To elucidate the functional role of BvSTI, its coding region was fused to the CaMV 35S promoter and constitutively expressed in sugarbeet (line F1010) hairy roots and Nicotiana benthamiana plants. In BvSTI-transformed F1010 hairy roots, trypsin inhibitory activity increased by 2- to 4-fold. Using a polyacrylamide gel assay, new trypsin-like PI activity was detected in BvSTI-N. benthamiana plants. Since SBRM cannot be reared in vitro, two other insects that utilize serine digestive proteases, fall armyworm (Spodoptera frugiperda) and tobacco hornworm (Manduca sexta), were screened for resistance. Fall armyworm fed on sugarbeet hairy roots. Tobacco hornworm that fed on BvSTI-N. benthamiana leaves showed reduced weight and pupal size. These results suggested that BvSTI may contribute to moderate resistance in F1016 roots to SBRM. The functional analysis of additional ESTs will further support efforts to characterize the components of sugarbeet root resistance mechanisms.