Molecular cloning and characterization of a cotton phosphoenolpyruvate carboxylase gene

Phosphoenolpyruvate carboxylase (PEPC) plays diverse physiological functions during plant development. In this study, a new phosphoenolpyruvate carboxylase gene GhPEPC2 is isolated from cotton (Gossypium hirsutum cv. zhongmian 35) by RACE-PCR. The cloned cDNA of GhPEPC2 is 3364 bp in length, and has an open reading frame of 2913 bp, encoding for 971 putative amino acids with a calculated molecular mass of 110.6 kD and pI of 5.56. The deduced amino acid sequence of GhPEPC2 shares high similarity with other reported plant PEPCs. Southern blot analysis indicates that the cotton PEPC exists as a small gene family and the GhPEPC2 might have two copies in the cotton genome. The semi-quantitative RT-PCR reveals that GhPEPC2 constitutively expresses in all the tissues of cotton and accumulated highly in roots, flowers and embryos but relatively low in stems and fibers. In addition, the recombinant GhPEPC2 has been purified by expressing it in Escherichia coli and the catalytic properties of it were also investigated. The results showed that GhPEPC2 is a typical C3 PEPC with a higher Km (83.6 μM) and lower Vmax (8.0 μmol min−1 mg−1) compared with the C3 PEPCs previously reported.