IHSM-UMA-CSIC La Mayora, Departamento de Biología Molecular y Bioquímica, Universidad de Málaga, 29071, Málaga, Spain.
IHSM-UMA-CSIC La Mayora, Plant breeding and Biotechnology, CSIC, 29750 Algarrobo-Costa, Málaga, Spain.
Plant Physiol. 2023 Jan 2;191(1):219-232. doi: 10.1093/plphys/kiac369.
The cuticle is a protective extracellular matrix that covers the above-ground epidermis of land plants. Here, we studied the cuticle of tomato (Solanum lycopersicum L.) fruits in situ using confocal Raman microscopy. Microsections from cuticles isolated at different developmental stages were scanned to visualize cuticle components with a spatial resolution of 342 nm by univariate and multivariate data analysis. Three main components, cutin, polysaccharides, and aromatics, were identified, with the latter exhibiting the strongest Raman scattering intensity. Phenolic acids and flavonoids were differentiated within the cuticle, and three schematic cuticle models were identified during development. Phenolic acids were found across the entire cuticle at the earliest stage of development, i.e. during the formation of the procuticle layer. Based on a mixture analysis with reference component spectra, the phenolic acids were identified as mainly esterified p-coumaric acid together with free p-hydroxybenzoic acid. During the cell expansion period of growth, phenolic acids accumulated in an outermost layer of the cuticle and in the middle region of the pegs. In these stages of development, cellulose and pectin were detected next to the inner cuticle region, close to the epidermal cell where flavonoid impregnation started during ripening. In the first ripening stage, chalconaringenin was observed, while methoxylated chalcones were chosen by the algorithm to fit the mature cuticle spectra. The colocation of carbohydrates, esterified p-coumaric acid, and methoxylated chalconaringenin suggests that the latter two link polysaccharide and cutin domains. Elucidating the different distribution of aromatics within the cuticle, suggests important functions: (1) overall impregnation conferring mechanical and thermal functions (2) the outermost phenolic acid layer displaying UV-B protection of the plant tissue.
表皮是覆盖陆地植物地上表皮的一种保护性细胞外基质。在这里，我们使用共聚焦拉曼显微镜原位研究了番茄（Solanum lycopersicum L.）果实的表皮。从不同发育阶段分离的表皮微切片进行扫描，通过单变量和多变量数据分析以 342nm 的空间分辨率可视化表皮成分。鉴定出三种主要成分：角质、多糖和芳烃，其中后者表现出最强的拉曼散射强度。在表皮内区分出了酚酸和类黄酮，并且在发育过程中鉴定出了三个示意性表皮模型。在发育的最早阶段，即在原表皮层形成时，即在整个表皮层中都发现了酚酸。基于参考组分光谱的混合物分析，鉴定出的酚酸主要为酯化的对香豆酸和游离的对羟基苯甲酸。在生长的细胞扩展期，酚酸积累在表皮的最外层和钉的中间区域。在这些发育阶段，纤维素和果胶检测到靠近内表皮区域，靠近表皮细胞，在成熟过程中黄酮类物质开始浸渍。在第一成熟阶段观察到查尔酮橙皮素，而算法选择甲氧基化查尔酮拟合成熟表皮的光谱。碳水化合物、酯化对香豆酸和甲氧基化查尔酮橙皮素的共定位表明后两者连接多糖和角质区域。阐明芳烃在表皮内的不同分布表明其具有重要功能：（1）整体浸渍赋予机械和热功能；（2）最外层的酚酸层显示对植物组织的 UV-B 保护。
