Characterization of STP4 promoter in Indian mustard Brassica juncea for use as an aphid responsive promoter

Brassica juncea, a major oilseed crop, suffers substantial yield losses due to infestation by mustard aphids (Lipaphis erysimi). Unavailability of resistance genes within the accessible gene pool underpins significance of the transgenic strategy in developing aphid resistance. In this study, we aimed for the identification of an aphid-responsive promoter from B. juncea, based on the available genomic resources.

A monosaccharide transporter gene, STP4 in B. juncea was activated by aphids and sustained increased expression as the aphids colonized the plants. We cloned the upstream intergenic region of STP4 and validated its stand-alone aphid-responsive promoter activity. Further, deletion analysis identified the putative cis-elements important for the aphid responsive promoter activity.

The identified STP4 promoter can potentially be used for driving high level aphid-inducible expression of transgenes in plants. Use of aphid-responsive promoter instead of constitutive promoters can potentially reduce the metabolic burden of transgene-expression on the host plant.