Changes of Morphology, Chemical Compositions, and the Biosynthesis Regulations of Cuticle in Response to Chilling Injury of Banana Fruit During Storage.

Hua Huang,Ling Wang,Diyang Qiu,Nan Zhang,Fangcheng Bi

doi:10.3389/fpls.2021.792384

Abstract

The plant cuticle covers almost all the outermost surface of aerial plant organs, which play a primary function in limiting water loss and responding to the environmental interactions. Banana fruit is susceptible to thermal changes with chilling injury below 13°C and green ripening over 25°C. Herein, the changes of surface morphology, chemical compositions of cuticle, and the relative expression of cuticle biosynthesis genes in banana fruit under low-temperature storage were investigated. Banana fruit exhibited chilling injury rapidly with browned peel appearance stored at 4°C for 6 days. The surface altered apparently from the clear plateau with micro-crystals to smooth appearance. As compared to normal ones, the overall coverage of the main cuticle pattern of waxes and cutin monomers increased about 22% and 35%, respectively, in browned banana stored under low temperature at 6 days. Fatty acids (C16–C18) and ω-OH, mid-chain-epoxy fatty acids (C18) dominated cutin monomers. The monomers of fatty acids, the low abundant ω, mid-chain-diOH fatty acids, and 2-hydroxy fatty acids increased remarkably under low temperature. The cuticular waxes were dominated by fatty acids (> C19), n-alkanes, and triterpenoids; and the fatty acids and aldehydes were shifted to increase accompanied by the chilling injury. Furthermore, RNA-seq highlighted 111 cuticle-related genes involved in fatty acid elongation, biosynthesis of very-long-chain (VLC) aliphatics, triterpenoids, and cutin monomers, and lipid-transfer proteins were significantly differentially regulated by low temperature in banana. Results obtained indicate that the cuticle covering on the fruit surface was also involved to respond to the chilling injury of banana fruit after harvest. These findings provide useful insights to link the cuticle on the basis of morphology, chemical composition changes, and their biosynthesis regulations in response to the thermal stress of fruit during storage.

Highlights

Banana is one of the most populated horticultural crops planted widely in the tropical and subtropical regions including south China
Banana fruit stored at 25◦C as control, the green peel appearance showed no obvious changes with trace of browning pot with most of them for mechanical damages during treatments after harvest (Figures 1A,B)
This study in detail reported the changes of appearance morphology, response of chemical compositions, and their biosynthesis regulation genes in banana cuticle under lowtemperature storage

Summary

Introduction

Banana fruit is sensitive to temperatures, which exhibits chilling injury below 13◦C and softening without normal yellow-colored under high temperature over 25◦C (Yang et al, 2009; Hashim et al, 2012). The chilling injury symptoms of banana fruit mainly exhibit as browning in the vascular tissues and appearance and abnormal flesh softening (Wang et al, 2012). The chilling injury with browning changes is widely reported to be regulated by the reactive oxygen species (ROS), antioxidant activity, ATP level, and ion concentration in banana fruit. The integrity of the plasma membrane, which is pivotal for quality maintenance, is altered or damaged under ROS, temperature, or other stress stimulations during storage (Huang et al, 2019)

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Discussion

Conclusion