Chemical and Transcriptomic Analysis of Cuticle Lipids under Cold Stress in Thellungiella salsuginea.

Junqing He,Minqi Zhou,Di Yang,Shuai Tang,Yue Chen,Ludi Ling,Yanli Zou,Xiaojing Xu

doi:10.3390/ijms20184519

Junqing He, Minqi Zhou + Show 6 more

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https://doi.org/10.3390/ijms20184519

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Abstract

Plant cuticle lipids form outer protective layers to resist environmental stresses; however, the relationship between cuticle properties and cold tolerance is unclear. Here, the extremophyte Thellungiella salsuginea was stressed under cold conditions (4 °C) and the cuticle of rosette leaves was examined in terms of epicuticular wax crystal morphology, chemical composition, and cuticle-associated gene expression. The results show that cold induced formation of distinct lamellas within the cuticle ultrastructure. Cold stress caused 14.58% and 12.04% increases in the amount of total waxes and cutin monomer per unit of leaf area, respectively, probably associated with the increase in total fatty acids. The transcriptomic analysis was performed on rosette leaves of Thellungiella exposed to cold for 24 h. We analyzed the expression of 72 genes putatively involved in cuticle lipid metabolism, some of which were validated by qRT-PCR (quantitative reverse transcription PCR) after both 24 h and one week of cold exposure. Most cuticle-associated genes exhibited higher expression levels under cold conditions, and some key genes increased more dramatically over the one week than after just 24 h, which could be associated with increased amounts of some cuticle components. These results demonstrate that the cuticle provides some aspects of cold adaptation in T. salsuginea.

Highlights

Extreme environmental conditions, including those caused by low temperatures, drought, and salt stress, pose serious threats to agricultural production [1]
To examine the change in the wax crystal structure under cold stress, scanning electron microscopy (SEM) was used to observe the organization of epicuticular wax crystals covered on the rosette leaves of T. salsuginea
No obvious changes were observed on the abaxial surface after cold treatment, probably due to only few and sparsely distributed wax crystals being produced on the abaxial surface of the rosette leaves of T. salsuginea (Figure 1C1,C2)

Summary

Introduction

Extreme environmental conditions, including those caused by low temperatures, drought, and salt stress, pose serious threats to agricultural production [1]. Temperature is an important abiotic factor affecting plant physiological processes [2]. Plants can endure or resist low temperature stress by accumulating internal osmotic adjustment substances including proline, betaine, and soluble sugar [3], and increasing the synthesis of metabolism-related proteins, molecular chaperones, and antifreeze proteins [4,5]. Wax is a mixture of substances that are soluble in organic solvents, usually including very long chain fatty acids (VLCFAs), alkanes, alcohols, fatty aldehydes, ketones, and esters [14]. The cutin monomers normally include unsubstituted fatty acids, ω- and mid-chain hydroxy and epoxy fatty acids, and α and ω-dicarboxylic acids, and they can have diverse kinds of interlinkages [17]. Variations in cutin composition and ultrastructure have been associated with the physiological functions of cutin [17]

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