Expression of selected nuclear genes during leaf development in barley

Abstract

AbstractGroups of cDNA clones encoding abundant leaf proteins or derived from genes (gene families) with other features of interest have been selected from a barley leaf cDNA library. The characteriaztion of nine of the groups is summarized and includes information on the tissue specificity and light dependence of expression of their corresponding genes. Different types of control of gene expression are represented in the collection: leaf‐specific expression, both stimulated and inhibited by light, constitutive expression, and expression that is maximal in one case in coleoptiles and in two cases in meristematic tissue. For the light‐stimulated genes (gene families) encoding chloroplast proteins (Cab, RbcS, and plastocyanin), relative and absolute levels of messengers were determined as a function of cell age in sections of 7‐day‐old barley leaves grown under diurnal conditions. Key parameters of cell growth (protein, RNA, and DNA accumulation) were determined in the same leaf sections. The main conclusions of the expression studies are as follows: (1) Light is in no case a requirement for gene expression although it has significant stimulatory effect on some genes; (2) weak expression of some genes coding for chloroplast proteins was detected in the leaf‐like, white coleoptiles, whereas expression in roots could not be detected; (3) The cab, rbcS, and plastocyanin genes are expressed very early during leaf cell differentiation, when the plastids morphologically are still in their amyloplast‐amoeboid stages; (4) The expression of the cab, rbcS, and plastocyanin genes is not coordinated during leaf cell development.