Analysis of the promoter activity of late embryogenesis abundant protein genes in barley seedlings under conditions of water deficit

Promoters of the late embryogenesis abundant protein genes, HVA1s, Dhn8s and Dhn4s from barley and wsi18j and rab16Bj from rice, were analysed in barley seedlings to assess their strength and timing of induction under water deficit conditions using a transient expression system. Of the drought-inducible promoters, Dhn4s exhibited the highest activity, followed by HVA1s, wsi18j and rab16Bj. Dehydration-induced #-glucuronidase expression levels driven by the Dhn4s, HVA1s and wsi18j promoters were higher than or comparable to that induced by a strong constitutive rice Act1 promoter. The expression patterns of wsi18j and Dhn8s differed from those of their homologous genes (wsi18 and Dhn8): the wsi18j promoter was strongly induced by abscisic acid, while the Dhn8s promoter was highly active in hydrated seedlings. HVA1s- and wsi18j-driven green fluorescent protein expression was induced within 1 h of drying under water deficit stress, while Dhn4s promoter activity was not detectable until 3 h, thus showing a difference in the timing of induction.