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

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.

Defensive Responses of Tea Plants (Camellia sinensis) Against Tea Green Leafhopper Attack: A Multi-Omics Study

“…In total, 354-393 compounds were detected from the wax mixtures of CK samples (n = 3) and 397-414 compounds were detected from those of LD samples (n = 3) (Supplemental Table S12). The wax mixtures on sampled tea leaves from both groups consisted mainly of fatty acids, alkanes, alkenes, aldehydes, and primary alcohols, similar to a recent report on the predominant wax constituents of tender tea leaves (Zhu et al, 2018) ( Table 3).…”

“…To compare the differences in leaf wax compositions between CK and LD groups, total cuticular wax was extracted and analyzed as previously described (Zhu et al, 2018). Tea leaves were soaked with 5 ml of chloroform containing 10 µg of n-tetracosane (internal standard) for 30 s at room temperature.…”

“…Aliquots of derivatized samples were separately injected into GCMS-QP2010 Ultra (Shimadzu, Japan) and GC-2010 Plus (Shimadzu, Japan) systems both equipped with an Agilent DB-1 capillary column (30 m x 0.25 mm i.d., 0.25 µm film thickness) for gas chromatography-mass spectrometry (GC-MS) and gas chromatography-flame ionization detector (GC-FID) analyses, respectively. The instrument settings were exactly the same as previously reported (Zhu et al, 2018). The alkane mix standard comprising C10 to C40 was diluted to 100 ng/µl with hexane and 1 µl was injected into GC-MS and GC-FID to assist with metabolite identification.…”

“…In tea plants, investigations on wax biosynthesis and its involvement in responding to biotic and abiotic stresses have not yet been undertaken. In fact, there have only been a couple of reports comparing the cuticle and wax compositions between different tea cultivars or between leaf tissues from different developmental stages (Tsubaki et al, 2013;Zhu et al, 2018). It is not clear whether CER1 homologs in tea plants perform the same function as in other plants.…”

Drought stress modify cuticle of tender tea leaf and mature leaf for transpiration barrier enhancement through common and distinct modes

“…After bud break new leaves are sequentially emerged, thus form a developmental gradient along the new branch: the leaves next to the apical bud are newly developed and are more tender; in contrast, the leaves located at the lower part of the branch are emerged earlier thus more mature. Along this developmental gradient, Zhu et al 3 demonstrated that leaf cuticular wax experienced dramatic compositional changes with leaf maturation: alicyclic compounds did not present from the tender second leaf but dominate the mature fifth leaf. Thus, in this study only the second leaf and the fifth leaf were selected to represent the tender leaf and mature leaf, respectively.…”