Molecular cloning, expression and computational analysis of a water stress inducible copper-containing amine oxidase gene (CuAO) from tea plant [Camellia sinensis (L.) O. Kuntze]

Abstract

Copper-containing amine oxidase (CuAO) is the enzyme known to play diversity of function in plant responses to environmental stresses through its reaction products. Here, for the first time we report full length cDNA encoding CuAO protein from a drought tolerant tea cultivar. It was found to be 785 bp long with a 70 bp 5.-UTR, 193 bp 3.-UTR, 522 bp mORF and a polyA adenylational signal. It codes for a poly-peptide of 173 amino acids having predicted molecular weight and isoelectric point of 19 KDa and 7.75 respectively. Heterologous expression and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis of the protein in Escherichia coli revealed similar size as predicted by in silico analysis. Blastp analysis and template based homology modeling in Phyre2 has identified a copper amine oxidase domain with ligand binding site for copper at residue 123 (Histidine) which suggests its probable role in plant responses to environmental stresses. Interestingly, no signal peptide sequence was detected in the predicted protein which is in contrast to the CuAO so far reported in plants. Although, in slico analysis of the protein have indicated its probable structure and functions, further functional characterization is needed to better understand its role during drought and other environmental stresses in tea.

Key words: Camellia sinensis, copper amine oxidase, homology modeling, molecular cloning.