Analysis of xyloglucan endotransglycosylase/hydrolase (XTH) genes and diverse roles of isoenzymes during persimmon fruit development and postharvest softening.

Ye Han,Qinggang Zhu,Yali Hou,Jingping Rao,Qiuyan Ban,Kun Meng,Jiangtao Suo,Zhengke Zhang

doi:10.1371/journal.pone.0123668

Ye Han, Qinggang Zhu + Show 6 more

Open Access

https://doi.org/10.1371/journal.pone.0123668

Copy DOI

Abstract

Xyloglucan endotransglycosylase/hydrolase (XTH) enzymes have played a role in the remodeling of cell wall hemicelluloses. To investigate the function of XTHs in persimmon (Diospyros kaki L.) fruit development and postharvest softening, five cDNAs (DkXTH1 to DkXTH5), whose putative proteins contained the conserved DEIDFEFLG motif of XTH, were cloned. Real time quantitative PCR analysis revealed that DkXTH1, DkXTH4, and DkXTH5 peaked in immature expanding fruit, and their higher expression was observed along with higher fruit firmness in cold-treated fruit or firmer cultivar fruit during storage. The opposite gene expression patterns were observed in DkXTH2 and DkXTH3, which reached maxima concomitance with pronounced fruit softening. Meanwhile, the xyloglucan endotransglycosylase (XET) enzymes play important roles in both the rapid growth and ripening of persimmon fruit. Furthermore, the recombined DkXTH1 and DkXTH2 proteins showed significant XET activity without any detected XEH activity. However, the XET activity of recombined DkXTH2 protein had a higher affinity for small acceptor molecules than that of recombined DkXTH1 protein. The former might prefer to participate in cell wall restructuring, and the latter is more inclined to participate in cell wall assembly. Besides, DKXTH proteins could function by targeting to the cell wall under regulation of a signal peptide. The data suggested that individual DKXTHs could exhibit different patterns of expression, and the encoded products possessed specific enzymatic properties conferring on their respective functions in growth and postharvest softening of persimmon fruit.

Highlights

Persimmon (Diospyros kaki L.) is an important horticultural commodity with high market value because of its favorable flavor, distinct taste and components, and high nutritional value [1,2]
Three full-length sequences, designated DkXTH3–5, were isolated from persimmon fruit and all genes were deposited in GenBank with the accession numbers shown in Table 1, column 2
Full-length DkXTH2 fusion protein (DkXTH2Full) was located in the cell wall. These results indicated that the coding proteins of DkXTH1 and DkXTH2 were targeted to the cell wall by their N-terminal signal peptide

Summary

Introduction

Persimmon (Diospyros kaki L.) is an important horticultural commodity with high market value because of its favorable flavor, distinct taste and components, and high nutritional value [1,2]. The fruit is quite perishable and susceptible to softening after harvest, which. Diverse Roles of XTH Isoenzymes in Persimmon Fruit leads to deteriorated quality and major economic losses [3,4]. Fruit softening is considerably attributed to the catabolism of cell wall components. During fruit ripening and softening, pectic and hemicellulosic polysaccharides are the predominant cell wall components undergoing depolymerization and solubilization [5]. These processes involve the coordinated and interdependent action of some cell wall hydrolytic enzymes, including polygalacturonase, pectin methylesterase, pectate lyase, β-galactosidase, expansin, and xyloglucan endotransglycosylase/ hydrolase (XTH) [5,6,7,8]

Methods

Results

Conclusion