Transcriptome Sequencing and Differential Expression Analysis Reveal Molecular Mechanisms for Starch Accumulation in Chestnut

Shengxing Li,Haiying Liang,Wenhui Liang,Liang Tao,Zhiheng Zhao,Liquan Xiong,Zhuogong Shi

doi:10.3390/f11040388

Abstract

Chestnuts are popular edible nuts that are rich in starch. In order to enhance the transcriptomic resources and further understand starch and sucrose metabolism in maturing chestnuts, a comparative transcriptomic study of Chinese chestnut kernels was conducted at three ripening stages (70, 82, and 94 DAF). At 82 and 94 days after flowering (DAF), starch continued to accumulate, and the amylopectin/amylose ratio increased. Transcriptomic profiling of kernels at 70 (stage I), 82 (stage II), and 94 DAF (stage III) indicated that soluble starch synthase and α-1,4-glucan branching enzyme genes are actively expressed at 82 and 94 DAF. The starch degradation enzymes amylase, phosphoglucan phosphatase DSP4, and maltose exporter did not show differential gene expression, while glycogen phosphorylase-encoding unigenes were significantly down-regulated at 94 DAF. In addition to starch and sucrose metabolism, RNA transport, RNA degradation, pyrimidine metabolism, purine metabolism, plant hormone signal transduction, plant–pathogen interactions, and glycerophospholipid metabolism were found to be significantly enriched in all comparisons included in the study. As Chinese chestnut matured, the unique enriched pathways switched from ribosomal biogenesis and RNA polymerase of eukaryotes to endocytosis and spliceosomes. These genomic resources and findings are valuable for further understanding starch and sucrose metabolism in the Chinese chestnut.

Highlights

Chinese chestnut (Castanea mollissima Blume), a member of the Fagaceae family, is native to the Chinese mainland, Taiwan, and Korea
Starch analysis showed that the amylopectin content gradually increased during nut maturation, with the smallest amount detected at stage I and the highest amount observed at stage III
The dynamics of the total starch content were the same as those of the amylopectin content, whereas the amylose content decreased by stage III

Summary

Introduction

Chinese chestnut (Castanea mollissima Blume), a member of the Fagaceae family, is native to the Chinese mainland, Taiwan, and Korea. Several studies on Chinese chestnuts have found that the starch content and ratio of amylose to amylopectin affect the quality and taste of the nuts and are important factors in determining how the nuts are to be processed and their applications. Cultivars with a low amylose content are more suitable for the production of thermally processed chestnut kernels [3]. Yu et al [4] reported a positive relationship between turbidity, gel hardness, and chewiness and the retrogradation degree of the starch to amylose content in Chinese chestnut, and negative relationships among swelling power, thermal enthalpy, and cohesiveness. The major component of Chinese chestnut starch is amylopectin, of which the content is approximately 2−3 times that of amylose in it [5]. Similar results were obtained by Chen et al [6]

Methods

Results

Discussion

Conclusion