Abstract
Malate dehydrogenases (MDHs) are key metabolic enzymes that play important roles in plant growth and development. In the present study, we isolated the full-length and coding sequences of BraMDH from Chinese cabbage [Brassica campestris L. ssp. pekinensis (Lour) Olsson]. We conducted bioinformatics analysis and a subcellular localization assay, which revealed that the BraMDH gene sequence contained no introns and that BraMDH is localized to the chloroplast. In addition, the expression pattern of BraMDH in Chinese cabbage was investigated, which revealed that BraMDH was heavily expressed in inflorescence apical meristems, as well as the effect of BraMDH overexpression in two homozygous transgenic Arabidopsis lines, which resulted in early bolting and taller inflorescence stems. Furthermore, the fresh and dry weights of aerial tissue from the transgenic Arabidopsis plants were significantly higher than those from the corresponding wild-type plants, as were plant height, the number of rosette leaves, and the number of siliques produced, and the transgenic plants also exhibited stronger aluminum resistance when treated with AlCl3. Therefore, our results suggest that BraMDH has a dramatic effect on plant growth and that the gene is involved in both plant growth and aluminum resistance.
Highlights
Malate plays a key role in plant nutrition and metabolism, as an important intermediate product (Schulze et al, 2002; Scheibe, 2004) and is generated by malate dehydrogenases (MDHs: EC 1.1.1.82 or EC 1.1.1.37), which function as oxidoreductases that catalyze the reversible reactions of malate and oxaloacetic acid, using NAD+ or NADP+ as coenzymes
Localization of BraMDH in Chloroplast. Both iPSORT and TargetP identified a putative chloroplast transit peptide in the BraMDH amino acid sequence, and the colocalization of chlorophyll autofluorescence and BraMDH-GFP fusion protein fluorescence in Arabidopsis protoplasts confirmed that BraMDH was a chloroplast protein (Figure 2)
The expression level of BraMDH was highest in the inflorescence apical meristem, followed by the levels observed in flower buds, flower, young siliques, leaves, and inflorescence stems, respectively (Figure 3), and the expression level in inflorescence apical meristem was more than twice that in leaves
Summary
Malate plays a key role in plant nutrition and metabolism, as an important intermediate product (Schulze et al, 2002; Scheibe, 2004) and is generated by malate dehydrogenases (MDHs: EC 1.1.1.82 or EC 1.1.1.37), which function as oxidoreductases that catalyze the reversible reactions of malate and oxaloacetic acid, using NAD+ or NADP+ as coenzymes. The occurrence of MDHs is widespread in plants, animals, and microorganisms. Several MDH isoforms possess specific subcellular locations and coenzymes. According to their subcellular location, plant MDHs are classified as mitochondrial, peroxisomal, plastidial, and cytosolic MDHs (Gietl, 1992). In the model plant Arabidopsis thaliana, nine MDHs have been identified, including two peroxisomal MDHs (Pracharoenwattana et al, 2007; Eubel et al, 2008), two mitochondrial MDHs
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