Differential Regulation of Transcripts Encoding Cytosolic NADP-Malic Enzyme in C3 and C4 Flaveria Species

Abstract

Abstract A cytosolic NADP-malic enzyme (CYTME) has been described previously in several plants, all C3 species. CYTME is distinct from the chloroplastic NADP-malic enzyme (CHLME) that is highly active in C4 species. We show that at least oneCytMe gene is present in all Flaveriaspp., including C3, C4, and C3-C4 intermediate types. Based on theCytMe expression patterns in Flaveria pringlei (C3) and Flaveria trinervia(C4), we suggest CYTME has several distinct roles, including the supplying of NADPH for cytosolic metabolism, the supporting of wound response or repair, and the balancing of cellular pH in illuminated leaves. These three roles are likely correlated withCytMe mRNAs of apparent sizes 2.0, 2.2, and 2.4 kb, respectively, which differ in the length of the 5′ untranslated regions. Various regulatory mechanisms involving RNA processing and translational efficiency are discussed.