Molecular characterization and primary functional analysis of PeMPEC, a magnesium-protoporphyrin IX monomethyl ester cyclase gene of bamboo (Phyllostachys edulis).

KEY MESSAGE: A homologous gene of MPEC from Phyllostachys edulis was isolated and characterized. Its overexpression in Arabidopsis thaliana increased chlorophyll concentration and photosynthesis efficiency, indicating it is involved in chlorophyll biosynthesis. Magnesium-protoporphyrin IX monomethyl ester cyclase (MPEC) is an essential enzyme in the biosynthesis of chlorophyll, which plays an important role in photosynthesis. However, limited information is available on the roles of MPEC gene in bamboo. A homologous gene, PeMPEC was identified from Phyllostachys edulis, which comprised 1474 bp and contained an open reading frame encoding 415 amino acids. PeMPEC was transcribed abundantly in leaf blade where photosynthesis predominantly occurs, which agreed with the protein accumulation pattern confirmed by Western blotting. The PeMPEC transcription was promoted by continuous darkness for 24 h, and was suppressed by increasing light intensity (100-1500 µmo1 m(-2) s(-1)) and high temperature (42 °C). However, transcription was induced within 0.5 h and thereafter declined with prolonged treatment (up to 12 h) under low temperature (4 °C). Although PeMPEC expressed weakly in etiolated leaves, transcript levels increased gradually with subsequent light treatment (200 µmol m(-2) s(-1)). Overexpression of PeMPEC in Arabidopsis thaliana resulted in increased chlorophyll concentration and photosynthesis efficiency in sense transgenic plants compared with a reduction in antisense transgenic plants. These changes were consistent with the transcript levels of PeMPEC. These results indicated that PeMPEC might be involved in chlorophyll biosynthesis and play important roles in maintaining the stability of photosystems, and provide a basis for the study of chlorophyll biosynthesis and dissection of photosynthesis in bamboo.