Genome-Wide Identification and Functional Analysis of Carboxylesterase and Methylesterase Gene Families in Peach (Prunus persica L. Batsch).

Xiangmei Cao,Kunsong Chen,Bo Zhang,Chunyan Wei,Wenyi Duan,Don Grierson

doi:10.3389/fpls.2019.01511

Xiangmei Cao, Kunsong Chen + Show 4 more

Open Access

https://doi.org/10.3389/fpls.2019.01511

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Abstract

Carboxylesterases (CXE) and methylesterases (MES) are hydrolytic enzymes that act on carboxylic esters and are involved in plant metabolic processes and defense responses. A few functions of plant CXE and MES genes have been identified but very little information is available about the role of most members. We made a comprehensive study of this gene family in a commercially important species, peach (Prunus persica L. Batsch). A total of 33 peach CXE genes and 18 MES genes were identified and shown to be distributed unevenly between the chromosomes. Based on phylogenetic analysis, CXEs and MESs clustered into two different branches. Comparison of the positions of intron and differences in motifs revealed the evolutionary relationships between CXE and MES genes. RNA-seq revealed differential expression patterns of CXE/MESs in peach flower, leaf, and ripening fruit and in response to methyl jasmonate (MeJA) and ultraviolet B treatment. Transcript levels of candidate genes were verified by real-time quantitative PCR. Heterologous expression in Escherichia coli identified three CXEs that were involved in the hydrolysis of volatile esters in vitro. Furthermore, two recombinant MES proteins were identified that could hydrolyze MeJA and methyl salicylate. Our results provide an important resource for the identification of functional CXE and MES genes involved in the catabolism of volatile esters, responses to biotic and abiotic stresses and activation of signaling molecules such as MeJA and methyl salicylate.

Highlights

Carboxylesterases (CXEs, EC 3.1.1.1) are ubiquitous enzymes which are present in all domains of life including some viruses
Plant CXEs were divided into three classes in previous literature (Gershater and Edwards, 2007), class I mainly contains the previously annotated plant CXE family, including tobacco hsr203J and AtCXE1-20 in Arabidopsis (Marshall et al, 2003); class II contains SA-binding protein (SABP2) from tobacco and methyl jasmonate esterase (MJE) from tomato; class III CXEs are related to the GDS lipases
20 genes with high sequence similarities to SABP2 were identified in Arabidopsis and phylogenetic analysis showed that they cluster into a clade that is distant from previously named AtCXEs (Yang et al, 2008)

Summary

Introduction

Carboxylesterases (CXEs, EC 3.1.1.1) are ubiquitous enzymes which are present in all domains of life including some viruses. 20 genes with high sequence similarities to SABP2 were identified in Arabidopsis and phylogenetic analysis showed that they cluster into a clade that is distant from previously named AtCXEs (Yang et al, 2008). Due to their specific hydrolysis activity towards methyl jasmonate (MeJA), methyl salicylate (MeSA), and methyl indole-3-acetate (MeIAA), they were named the methylesterase (MES) family (Yang et al, 2008). For the sake of distinction and understanding, we name these two classes as CXE and MES families respectively, following the Arabidopsis nomenclature

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