Systematic Analysis and Biochemical Characterization of the Caffeoyl Shikimate Esterase Gene Family in Poplar

Abstract

Caffeoyl shikimate esterase (CSE) hydrolyzes caffeoyl shikimate into caffeate and shikimate in the phenylpropanoid pathway. In this study, we performed systematic analysis of CSE gene family in poplar and investigated the possible roles of CSEs and CSE-like genes in Populus. We performed a genome-wide analysis of the CSE family, including functional and phylogenetic analyses of CSE and CSE-like genes using the poplar (Populus trichocarpa) genome. Eighteen CSE and CSE-like genes were identified in the Populus genome and five phylogenetic groups were identified from phylogenetic analysis. CSEs in Group Ia, which were proposed as bona fide CSEs, have probably been lost in most monocots except Oryza sativa. Primary functional classification showed that PoptrCSE1 and PoptrCSE2 had putative function in lignin biosynthesis. In addition, PoptrCSE2, along with PoptrCSE12 might also respond to stress with a function in cell wall biosynthesis. Enzymatic assay of Populus tomentosa (Popto) CSE1, -2 and -12 showed that PoptoCSE1 and -2 kept CSE activity. PoptoCSE1 and 2 had similar biochemical properties, tissue expression pattern and subcellular localization. Most of the PoptrCSE-like genes are homologs of AtMAGL (monoacylglycerol lipase) genes in Arabidopsis and may function as MAG lipase in poplar. Our study provides systematic understanding of this novel gene family and suggests the CSE function in monolignol biosynthesis in Populus.