University of Würzburg, Julius von Sachs Institute for Biosciences, Würzburg, Germany.
University of Basel, Swiss Nanoscience Institute-Nano Imaging Lab, Basel, Switzerland.
PLoS One. 2021 Feb 19;16(2):e0246693. doi: 10.1371/journal.pone.0246693. eCollection 2021.
The grapevine berry surface is covered by a cuticle consisting of cutin and various lipophilic wax compounds. The latter build the main barrier for transpirational water loss and protect the fruit against environmental factors e.g. pests, mechanical impacts or radiation. The integrety of the fruit surface is one important key factor for post-harvest quality and storage of fruits. Nonetheless, the developmental pattern of cuticular wax was so far only investigated for a very limited number of fruits. Therefore, we performed comparative investigations on the compositional and morphological nature of epicuticular wax crystals and underlying wax during fruit development in Vitis vinifera. The main compound oleanolic acid belongs to the pentacyclic triterpenoids, which occur very early in the development in high amounts inside the cuticle. The amount increases until veraison and decreases further during ripening. In general, very-long chain aliphatic (VLCA) compounds are present in much smaller amounts and alcohols and aldehydes follow the same trend during development. In contrast, the amount of fatty acids constantly increases from fruit set to ripening while wax esters only occur in significant amount at veraison and increase further. Wax crystals at the fruit surface are solely composed of VLCAs and the morphology changes during development according to the compositional changes of the VLCA wax compounds. The remarkable compositional differences between epicuticular wax crystals and the underlying wax are important to understand in terms of studying grape-pest interactions or the influence of environmental factors, since only wax crystals directly face the environment.
葡萄浆果表面被一层由角鲨烯和各种疏水性蜡化合物组成的角质层覆盖。后者构成了蒸腾失水的主要屏障，并保护果实免受环境因素的影响，如害虫、机械冲击或辐射。果实表面的完整性是影响果实采后质量和贮藏的一个重要关键因素。尽管如此，角质层蜡的发育模式迄今为止仅在非常有限数量的果实中进行了研究。因此，我们对酿酒葡萄果实发育过程中表皮蜡晶体和下表皮蜡的组成和形态性质进行了比较研究。主要化合物齐墩果酸属于五环三萜类化合物，在发育早期大量存在于角质层内部。在转色期，其含量增加，然后在成熟过程中进一步减少。总的来说，非常长链脂肪族（VLCA）化合物的含量要低得多，醇和醛在发育过程中也呈现出相同的趋势。相比之下，脂肪酸的含量从果实开始到成熟不断增加，而蜡酯仅在转色期大量存在，并进一步增加。果实表面的蜡晶体仅由 VLCAs 组成，其形态在发育过程中根据 VLCA 蜡化合物的组成变化而变化。角质层蜡晶体和下表皮蜡之间的显著成分差异对于研究葡萄与害虫的相互作用或环境因素的影响非常重要，因为只有蜡晶体直接面对环境。
