Genome-wide analysis of 1-amino-cyclopropane-1- carboxylate synthase gene family in <i>Arabidopsis</i>, rice, grapevine and poplar

Abstract

Ethylene is an important hormone that is involved in a number of developmental processes and stress responses in higher plants. 1-Aminocyclopropane-1-carboxylate synthase (ACC) synthase as a key enzyme of the ethylene biosynthesis pathway, is in great need to be well studied. Though some efforts have been made to elucidate the structure, catalytic activity and evolutionary relationships of ACC synthase, there has not been a comprehensive study performed to statistically evaluate sequence conservation and functional divergence in this family. Our study was performed in four sequenced species, Arabidopsis, rice, grapevine and poplar, to determine the evolution mode in ACS gene family. Genome wide screening identified 12 ACS genes in Arabidopsis, six in rice, 10 in grapevine and 11 in poplar, while evolutionary pattern, site-specific dN/dS ratio tests, branch-site dN/dS ratio tests and diverge analysis were employed on their sequence. The results show that evolutionary pattern were quiet different in these four species, while strong purifying selection played the most important roles during evolution of the ACS gene family, and altered functional constraints may have taken place at some amino acid residues among main lineages (A1, A2, A3 and B). Besides, we mapped 11 residues that were probably involved in functional diverge of ACS family onto the sequence logo and threedimensional structure of Arabidopsis ACS1 to get more understanding of their functional diversity. In all, our results provide solid information for better understanding of the function and evolution of the ACS gene family in higher plants.

Key words: ACC synthase, phylogenetic, positive selection, functional divergence.