Characterization and analysis of CCR and CAD gene families at the whole-genome level for lignin synthesis of stone cells in pear (Pyrus bretschneideri) fruit.

Xi Cheng,Lingling Sheng,Manli Li,Jinyun Zhang,Yi Lin,Yongping Cai,Dahui Li,Qing Jin

doi:10.1242/bio.026997

Abstract

ABSTRACTThe content of stone cells has significant effects on the flavour and quality of pear fruit. Previous research suggested that lignin deposition is closely related to stone cell formation. In the lignin biosynthetic pathway, cinnamoyl-CoA reductase (CCR) and cinnamyl alcohol dehydrogenase (CAD), dehydrogenase/reductase family members, catalyse the last two steps in monolignol synthesis. However, there is little knowledge of the characteristics of the CCR and CAD families in pear and their involvement in lignin synthesis of stone cells. In this study, 31 CCRs and 26 CADs were identified in the pear genome. Phylogenetic trees for CCRs and CADs were constructed; key amino acid residues were analysed, and three-dimensional structures were predicted. Using quantitative real-time polymerase chain reaction (qRT-PCR), PbCAD2, PbCCR1, -2 and -3 were identified as participating in lignin synthesis of stone cells in pear fruit. Subcellular localization analysis showed that the expressed proteins (PbCAD2, PbCCR1, -2 and -3) are found in the cytoplasm or at the cell membrane. These results reveal the evolutionary features of the CCR and CAD families in pear as well as the genes responsible for regulation of lignin synthesis and stone cell development in pear fruit.

Highlights

Pear, an important fruit species of Rosaceae, is widely distributed throughout the world
Twenty-six members of the pear cinnamyl alcohol dehydrogenase (CAD) family were identified from the pear genome database based on the conserved domains of nine members of the CAD family in Arabidopsis (Raes et al, 2003)
With the completion of genome sequencing of several species, screening and identification of the two families of lignin biosynthesis-related members have been performed in P. trichocarpa, O. sativa, Lolium perenne and other plants (Shi et al, 2010; Hirano et al, 2012; Carocha et al, 2015; Van Parijs et al, 2015)

Summary

Introduction

An important fruit species of Rosaceae, is widely distributed throughout the world. Dangshan Su), originating in Dangshan County, Anhui Province, China, is a well-known diploid cultivar (2n=34) due to its high value in the fresh fruit market as well as for its medicinal properties (Konarska, 2013; Wu et al, 2013; Yan et al, 2014). Factors such as the size, content and density of stone cells in pear are thought to greatly affect pear quality (Jin et al, 2013; Cheng et al, 2016).

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