Cloning, identification, expression analysis and phylogenetic relevance of two NADP-dependent malic enzyme genes from hexaploid wheat

Abstract

The NADP-dependent malic enzyme (NADP-ME; EC1.1.1.40) found in many metabolic pathways catalyzes the oxidative decarboxylation of L-malate, producing pyruvate, CO 2 and NADPH. The NADP-MEs have been well studied in C4 plants but not well in C3 plants. In this study, we identified the NADP-ME isoforms from hexaploid wheat (Triticum aestivum L). Two different NADP-ME transcripts were first identified in this C3 plant. The first is named TaNADP-ME1 [NCBI: EU170134] and encodes a putative plastidic isoform, while the second is named TaNADP-ME2 [NCBI: EU082065] and encodes a cytosolic counterpart. Sequence alignment shows that the two NADP-ME isoforms share an identity of 73.26% in whole amino acids and 64.08% in nucleotide sequences. The phylogenetic analysis deciphers the two NADP-MEs as belonging to the monocots (Group II), which closely resemble OschlME6 and OscytME2, respectively. Tissue-specific analyses indicate that the two NADP-ME genes are both expressed in root, stem and leaf, and that TaNADP-ME1 is a leaf-abundant isoform. Semi-quantitative RT-PCR analysis show that the two NADP-ME transcripts in wheat leaves respond differently to low temperature, salt, dark and drought stresses stimuli and to exogenous abscisic acid (ABA) and salicylic acid (SA). Our results demonstrate that exogenous hormones (ABA and SA), as well as salt, low temperature, dark and drought stresses can regulate the expressions of TaNADP-ME1 and TaNADP-ME2 in wheat. This indicates that the two NADP-ME genes may play an important role in the response of wheat to ABA, SA, low temperature, salt, dark and drought stress.

Evolutionary Insights on C4 Photosynthetic Subtypes in Grasses from Genomics and Phylogenetics

“…2), emphasizes the predispositions of this gene lineage to become C 4 specific. This lineage encodes the only plastidic isoform in rice (Chi et al 2004), maize (Tausta et al 2002), and wheat (Fu et al 2009). This is also the only gene lineage with a plastid transit peptide in Brachypodium and sorghum (fig.…”

“…Some NADP-me isoforms are expressed in the cytosol, whereas others, among which stand the C 4 ones, act in the chloroplasts (Edwards and Andreo 1992; Drincovich et al 2001). Nonphotosynthetic NADP-me plastid isoforms seem to be constitutively expressed and have been suggested to be involved in plastid biogenesis, fatty acid synthesis, defence pathways, and other nonphotosynthetic housekeeping functions (Maurino et al 2001; Lai, Wang et al 2002; Tausta et al 2002; Fu et al 2009). On the other hand, plastid isoforms of NADP-me acting in the C 4 pathway are highly expressed and upregulated by light in bundle–sheath cells of C 4 plants that use the NADP-me pathway (Maurino et al 1996; Drincovich et al 1998; Tausta et al 2002).…”

The corresponding relationship between roles of NADP-malic<br>enzymes and abiotic stress in plants

“…They will affect the CO 2 fixed, destroy the structure of chloroplast and reduce the content of chlorophyll. The last result is suppressing the photosynthesis and lowing the photosynthetic rate in wheat under drought stress (Ahmad et al, 2007;Sun et al, 2004;Fu et al, 2009).…”

“…It may be the first cytoplasmic NADP-ME gene found in C 3 plant. It is proved that TaNADP-ME 1 and TaNADP-ME 2 may play important role in stress tolerance (Fu et al, 2009).…”

Expression, purification and characterization of Oryza sativa L. NAD-malic enzyme in Escherichia coli

“…Moreover, it was considered that plant NADP-malic enzymes (NADP-MEs) were involved in plant defense responses. Plant NADP-MEs were induced by many biotic or abiotic stresses, such as pathogen (Sutherland, 1991), wounding, UV-B radiation (Casati et al, 1999), ABA, SA, low temperature, dark, salt and drought stress (Fu et al, 2009). The mechanism about stress resistance was postulated that the enzyme was implicated in defense-related deposition of lignin and flavonoid by providing NADPH for steps in their biosynthesis pathway requiring reductive power (Casati et al, 1999).…”