Drought stress occurs intermittently and severely constrains plant growth and production. Constitutive overexpression of stress-responsive genes can improve drought tolerance but often imposes unnecessary metabolic costs under favorable conditions. Stress-inducible promoters therefore represent an important regulatory resource for precision engineering of drought tolerance. In this study, a drought-inducible promoter from switchgrass ( Panicum virgatum L.), PvHVA1pro , derived from the late embryogenesis abundant gene PvHVA1 ( Hordeum vulgare aleurone 1 ) was identified and functionally validated. Transcript analysis showed that PvHVA1 expression is strongly induced by PEG-mediated osmotic stress, with minimal basal expression under non-stress conditions. Stable transgenic switchgrass expressing PvHVA1pro::GUS exhibited drought-dependent and reversible promoter activity in vegetative tissues. To demonstrate its practical utility, PvHVA1pro was used to drive the aquaporin gene PvPIP2;9 in switchgrass that the inducible expression of PvPIP2;9 enhanced drought tolerance, photosynthetic performance, and water-use efficiency compared with wild-type plants, without pronounced growth penalties. Together, these results establish PvHVA1pro as a sensitive, low-basal, drought-inducible promoter resource for switchgrass, providing an enabling regulatory tool for functional genomics and precision drought-tolerance engineering in bioenergy crops. • PvHVA1pro has a low basal activity and enables drought inducible gene expression in switchgrass. • PvHVA1pro activity is drought-dependent and reversible upon rewatering. • PvHVA1pro represents a regulatory resource for precision drought engineering in grasses.
Wen et al. (Sun,) studied this question.