Cloning and Transcription Expression Analysis of Magnesium-Protoporphyrin IX Monomethyl Ester Cyclase Gene in Cymbidium Hybrid

Magnesium-protoporphyrin IX monomethyl ester cyclase has been considered to be an important enzyme which related to chlorophyll biosynthesis. In order to explore the function of MPEC (Mg-protoporphyrin IX rnonomethyl ester cyclase) gene in leaf color variation, the cDNA of MPEC gene was successfully cloned from the leaves of Cymbidium hybrid ‘Purple Element’ (K21) and its new strain K21-3 by RT-PCR on the basis of transcriptome sequencing results in this study. Meanwhile, the biological information and expression of gene were analyzed. The ORF sequence lengths of ChMPEC1 and ChMPEC2 were both 1 221 bp, and they encoded 406 amino acids. There were two different amino acids in ChMPEC1 and ChMPEC2. Bioinformatics analysis showed that ChMPEC1 and ChMPEC2 might be stable hydrophilic proteins, and they belonged to the Ferritin-like family. The phylogenetic tree analysis showed that ChMPEC1 and ChMPEC2 of Cymbidium hybrid were closely related to that of Cymbidium sinense, Phalaenopsis equestris and Dendrobium catenatum from Orchidaceae. qPCR results indicated that the relative expression of ChMPEC in different tissues was as follows: leaves>stems>roots. The expression level of ChMPEC in descending order was at middle seedling stage, seedling stage and test-tube plantlets stage in the comparison of different development stages. Among the different strains, the expression level of ChMPEC in K21 was significantly higher than that of K21-3. Correlation analysis results showed that there were close correlations among ChMPEC gene expression, chlorophyll a, chlorophyll b and total chlorophyll. It was speculated that this gene was involved in the synthetic pathway of chlorophyll in Cymbidium hybrid and played a role in the formation of K21-3 leaf color variation. The above research results can provide a reference for the study on the formation mechanism of leaf color variation in Cymbidium hybrid.