Stress induction and developmental regulation of a rice chitinase promoter in transgenic tobacco

Abstract

SummaryA 1.5 kb promoter fragment from the rice (Oryza sativa L.) RCH10 gene, which encodes a basic endochitinase inducible by wounding and fungal elicitor, was translationally fused to the β‐glucuronidase (GUS) reporter gene and transferred to tobacco by Agrobacterium tumefaciens‐mediated leaf disc transformation. Wounding of leaves induced GUS activity from low basal levels, and addition of fungal elicitor to the wounded tissue caused a further marked activation of the gene fusion. During vegetative development high levels of GUS activity were observed in roots and moderate levels in stems. Histochemical analysis indicated that the promoter was active in vascular and epidermal tissue, and the root apical tip. In flowers, high levels of GUS activity were observed in stigmas, ovaries and pollen‐containing anthers, but only low levels in sepals and petals. The promoter 5′‐deleted to −160 exhibited the same patterns of expression in floral organs, and was also strongly induced by wounding and elicitor, but GUS activity was markedly reduced in vegetative organs. More detailed 5′ deletions showed that a cis‐element required for floral expression was located between −160 and −74, and a cis element sufficient for stress induction was located 3′ of −74. This proximal region 3′ of −74 was also sufficient for expression in transfected rice protoplasts derived from suspension cultured cells. These data indicate that the complex developmental and environmental regulation of RCH10 promoter activity involves several distinct cis‐elements for vegetative expression, floral expression and stress induction, and that signal pathways for wound and elicitor induction are conserved between monocotyledonous and dicotyledonous plants.