Molecular Mechanism of Xylogenesis in Moso Bamboo (Phyllostachys edulis) Shoots during Cold Storage.

Changtao Li,Wei Zeng,Lingling Xuan,Aimin Wu,Antony Bacic,Jie Wang,Yuming He,Lili Song,Hui Zhang,Yeqing Ying

doi:10.3390/polym11010038

Abstract

A bamboo shoot is the immature stem of the woody grass and a nutritious and popular vegetable in East Asia. However, it undergoes a rapid xylogenesis process right after harvest, even being stored in a cold chamber. To investigate the molecular regulation mechanisms of xylogenesis in Moso bamboo (Phyllostachys edulis) shoots (MBSes) during cold storage, the measurement of cell wall polymers (cellulose, hemicellulose, and lignin) and related enzyme activities (phenylalanine ammonia lyase (PAL), cinnamyl alcohol dehydrogenase (CAD), peroxidase (POD), and xylan xylosyltransferase (XylT)) and transcriptomic analysis were performed during cold storage. It was noticed that cellulose and lignin contents increased, while hemicellulose content exhibited a downward trend. PAL, CAD, and POD activity presented an upward trend generally in MBS when stored at 4 °C for 16 days. XylT activity showed a descending trend during the stages of storage, but slightly increased during the 8th to 12th days after harvest at 4 °C. Transcriptomic analysis identified 72, 28, 44, and 31 functional unigenes encoding lignin, cellulose, xylan biosynthesis enzymes, and transcription factors (TFs), respectively. Many of these secondary cell wall (SCW)-related genes showed higher expression levels in the later period of cold storage. Quantitative RT-PCR analysis of the selected genes conformed to the expression pattern. Our study provides a comprehensive analysis of MBS secondary wall biosynthesis at the molecular level during the cold storage process. The results give insight into the xylogenesis process of this economically important vegetable and shed light on solving this problem of the post-harvest industry.

Highlights

Moso bamboo (Phyllostachys edulis) shoots (MBSes) are immature, expanding culms emerging from nodes of therhizome of the bamboo plant, mainly in regions of Southern and EasternPolymers 2019, 11, 38; doi:10.3390/polym11010038 www.mdpi.com/journal/polymersChina
During the 16-day cold storage process, the cellulose content increased from 24.10% to 28.90%, and lignin increased from 11.85% to 15.62% (Table 1)
The vascular bundles showed little toluidine blue staining on day 0, whereas the staining showed deeper color as storage time progressed during cold storage

Summary

Introduction

Moso bamboo (Phyllostachys edulis) shoots (MBSes) are immature, expanding culms emerging from nodes of the (pseudo-)rhizome of the bamboo plant, mainly in regions of Southern and EasternPolymers 2019, 11, 38; doi:10.3390/polym11010038 www.mdpi.com/journal/polymersChina. There are approximately 1400 identified bamboo species around the world, and most of them produce shoots [1]. As rapidly growing subterraneous immature stems, MBSes deteriorate rapidly, which results in xylogenesis and decays, resulting in quality loss after harvest. This process occurs even when they are stored at low temperature, as evidenced by lignin deposition within the vascular bundles [2]. Luo et al [3] reported lignin and cellulose accumulation in fresh bamboo shoots during cold storage, accompanied by increases in phenylalanine ammonia lyase (PAL), cinnamyl alcohol dehydrogenase (CAD), and peroxidase (POD) activity

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Discussion

Conclusion