Primary Metabolism in Plant Defense (Regulation of a Bean Malic Enzyme Gene Promoter in Transgenic Tobacco by Developmental and Environmental Cues)

Abstract

NADP-dependent malic enzyme (NADP-ME, EC 1.1.1.40) catalyzes the oxidative decarboxylation of malate to pyruvate, producing CO, and NADPH. We have examined regulatory properties of a 2.8-kb promoter-leader fragment of a bean (Pbaseolus vurgaris 1.) NADP-ME gene (PvME1) predicted to encode a cytosolic form of the enzyme by expression analysis of promoter-P-glucuronidase fusions in transgenic tobacco plants. l h e PvMEl promoter directed strong expression in stems, which was confined to vascular and pith tissues, and was also active in floral and reproductive tissues. Wounding caused a marked induction of promoter activity, which was further strongly enhanced upon application of stimuli related to pathogen defense. Clutathione (reduced form) was the strongest inducer, but oxidized glutathione, funga1 elicitor, cellulase, catalase, ascorbic acid, and NADPH were additional potent promoterstimulating agents. Responsiveness to reduced glutathione was also shown at the leve1 of PvMEl mRNA accumulation in bean plants. l h e putative contributions of NADP-ME gene expression to the plant defense response and possible mechanisms of defense gene regulation by conditions of oxidative stress as well as by H,O, and antioxidant levels are discussed.

Loss of cytosolic NADP‐malic enzyme 2 in Arabidopsis thaliana is associated with enhanced susceptibility to Colletotrichum higginsianum

“…It has been known for quite a while that NADP-ME is induced in various abiotic stress conditions (Maurino et al, 2001;Liu et al, 2007) and during elicitor treatment and plant-pathogen interactions (Walter et al, 1988;Schaaf et al, 1995;Casati et al, 1997Casati et al, , 1999Maurino et al, 2001;Parker et al, 2009) and recently it was shown that NADP-ME induction proceeds more rapidly in incompatible compared with compatible interactions with B. distachyon (Parker et al, 2009). Consequently, the sites of NADP-ME induction and ROS production coincided during early infection with this hemibiotrophic fungus (Parker et al, 2009).…”

“…It has also been long speculated that nonphotosynthetic NADP-MEs would be involved in defence responses. It was shown that transcription of an NADP-ME gene in bean (Phaseolus vulgaris) was rapidly and transiently activated by fungal elicitor treatment in cell-suspension cultures (Walter et al, 1988) and that wounding caused a marked induction of NADP-ME promoter activity, which was also strongly induced upon application of stimuli related to pathogen defence, for example, reduced glutathione, fungal elicitor, cellulase and NADPH (Schaaf et al, 1995). NADP-ME was also shown to respond to plant defence elicitors in bean (Walter et al, 1994), wheat (Triticum aestivum; Casati et al, 1997) and maize (Zea mays; Maurino et al, 2001).…”

A Comprehensive Analysis of the NADP-Malic Enzyme Gene Family of Arabidopsis

“…Plastidic nonphotosynthetic isoforms were suggested to be involved in plant defense responses (Casati et al, 1999) and in lipid biosynthesis by providing carbon skeletons and reducing power (Smith et al, 1992;Eastmond et al, 1997). Cytosolic isoforms have also been linked to plant defense responses (Schaaf et al, 1995) and, in addition, to lignin biosynthesis by providing NADPH (Schaaf et al, 1995) and to control the cytosolic pH by balancing the synthesis and degradation of malate (Martinoia and Rentsch, 1994). Another suggested role for the NADP-ME is the control of stomatal closure by degrading malate during the day (Outlaw et al, 1981;Laporte et al, 2002).…”

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

“…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). The NADP-ME is widely distributed among all types of plants.…”