Expression of an NADP-malic enzyme gene in rice (Oryza sativa. L) is induced by environmental stresses; over-expression of the gene in Arabidopsis confers salt and osmotic stress tolerance

Abstract

NADP-malic enzyme (NADP-ME, EC 1.1.1.40) functions in many different pathways in plants, and has recently been implicated in plant defense such as in responses to wounding and UV-B radiation. In this study, we isolated a complementary DNA (cDNA) clone by using the differential display method and screening of a root cDNA library of rice (Oryza sativa. L) under carbonate (NaHCO3) stress, and identified it as one of the rice NADP-ME genes (we named it NADP-ME2, GenBank accession no. AB053295). The 5' end of NADP-ME2 was obtained by the 5'-RACE method, and the full-length cDNA had a length of 2217 bp encoding 593 amino acids. Expression of NADP-ME2 mRNA in roots was induced by stress from carbonates (NaHCO3 and Na2CO3, NaCl, and environmental pH changes. NADP-ME2 transcripts increased during 72-h exposures to NaHCO3, NaCl, and PEG stresses. Furthermore, NADP-ME activities in leaves and roots of rice seedlings increased by more than 50% in the presence of carbonates (NaHCO3 and Na2CO3), NaCl, and PEG. These results indicate that rice NADP-ME2 responds to salts and osmotic stresses. Transgenic Arabidopsis plants over-expressing NADP-ME2 were obtained through transformation, screening, Northern analysis and in situ NADP-ME activity assay. Transgenic Arabidopsis plants over-expressing NADP-ME2 grew well in 1/2 x MS medium with 100 mM NaCl or 4% mannitol, whereas growth of wild-type (WT) Arabidopsis seedlings was strongly inhibited. In addition, under 125 mM NaCl stress, the root lengths of transgenic lines were about twice as long as those of the WT. These results suggest that NADP-ME2 has a role in enhancing tolerance of plants to salt and osmotic stress.

Arbuscular mycorrhizal fungi enhances salinity tolerance ofPanicum turgidumForssk by altering photosynthetic and antioxidant pathways

“…Earlier enhanced NADP-ME activity has been reported to be correlated with enhanced stress tolerance. For example, in Oryza sativa, it has been demonstrated that exposure of stress enhances the transcript levels of NADP-ME (Cheng & Long 2007;Liu et al 2007). NADP malic enzymes are believed to participate in several important metabolic pathways and plant defense through malate metabolism (Casati et al 1999).…”

Three Different and Tissue-specific NAD-Malic Enzymes Generated by Alternative Subunit Association in Arabidopsis thaliana

“…To rule out the possibility of a nonspecific interaction of NAD-ME2 with the affinity column, E. coli expressing only NAD-ME2 without the His tag was similarly treated (Fig. 1A, lanes [5][6][7]. In this case, NAD-ME2 mature protein was detected in bacterial extracts (Fig.…”

Pathogen-induced changes in malate content and NADP-dependent malic enzyme activity in C3 or CAM performing Mesembryanthemum crystallinum L. plants

“…Malate decarboxylation by NADP-malic enzyme is associated with plant responses to biotic or abiotic stresses (Maurino et al 2001;Chi et al 2004;Smeets et al 2005;Liu et al 2007). This metabolic pathway was speculated to be involved as energy source for plant defense through the generation of pyruvate and NADPH (Casati et al 1999;Schaaf et al 1995).…”