Tender leaf and fully-expanded leaf exhibited distinct cuticle structure and wax lipid composition in Camellia sinensis cv Fuyun 6

Xiaofang Zhu,Mingjie Chen,Xin Zhou,Zhenghua Du,Weijiang Sun,Yi Zhang,Xiangrui Kong,Changsong Chen,Zijian Chen,Xiaobing Chen

doi:10.1038/s41598-018-33344-8

Abstract

The goal of the present study was to compare the structural and compositional differences of cuticle between tender leaf and fully-expanded leaf in Camellia sinensis, and provide metabolic base for the further characterization of wax biosynthesis in this economically important crop species. The tender second leaf and the fully-expanded fifth leaf from new twig were demonstrated to represent two different developmental stages, their cuticle thickness were measured by transmission electron microscopy. The thickness of the adaxial cuticle on the second and fifth leaf was 1.15 µm and 2.48 µm, respectively; the thickness of the abaxial cuticle on the second and fifth leaf was 0.47 µm and 1.05 µm, respectively. The thickness of the epicuticular wax layer from different leaf position or different sides of same leaf were similar. However, the intracuticular wax layer of the fifth leaf was much thicker than that of the second leaf. Total wax lipids were isolated from the second leaf and the fifth leaf, respectively. Gas chromatography-mass spectrometry analysis identified 51 wax constituents belonging to 13 chemical classes, including esters, glycols, terpenoids, fatty acids and their derivatives. Wax coverage on the second and fifth leaf was 4.76 µg/cm2 and 15.38 µg/cm2, respectively. Primary alcohols dominated in the tender second leaf. However, triterpenoids were the major components from the fully-expanded fifth leaf. The predominant carbon chains varied depending on chemical class. These data showed that the wax profiles of Camellia sinensis leaves are development stage dependent, suggesting distinct developmental dependent metabolic pathways and regulatory mechanisms.

Highlights

The plant cuticle covers almost all terrestrial plants, and plays multiple roles in the interaction between plants and the environment
We compared the cuticle and cuticular wax from the tender second leaf and the fully-expanded fifth leaf, we found that VLCFAs and their derivatives dominant in the cuticular waxes of the tender second leaf, while triterpenoids and steroids were the major components in the cuticular waxes of the fully-expanded leaf
Cross sections were prepared from different leaf positions, we observed that the epidermal cell size of the first leaf and the second leaf remained constant (Fig. 1c,d), become larger starting from the third leaf position (Fig. 1e,f)

Summary

Introduction

The plant cuticle covers almost all terrestrial plants, and plays multiple roles in the interaction between plants and the environment. It reduces non-stomatal water loss[1], protects plants from ultraviolet radiation[2], minimizes pollutant retention on leaf surfaces[3,4], defends against bacterial and fungal pathogens[5], participates in plant-insect interaction[6], regulates pollen-pistil interaction[7], and prevents organ fusion[8,9,10] These diverse functions are realized through the physical and chemical properties of cuticular waxes, a large volume of research had been dedicated to characterize cuticular waxes composition in different plant species[11,12,13,14,15,16,17]. This work provided metabolic base for the further characterization of cuticular wax biosynthesis in Camellia sinensis

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Results

Conclusion