BARD - understanding and improving quality traits in fruit: genetic manipulation of the tomato fruit cuticle

肉质果实的表皮由一层表皮细胞组成，表皮细胞上覆盖着一层厚厚的蜡质角质层。后者对于抵抗病原体和干旱，以及果实的外观（颜色，光泽度，质地），收获后处理的功效，储存，运输和货架期至关重要。因此，它是决定水果质量的一个非常重要的因素，因此也是顾客偏好的一个重要因素。为了改善果实品质，必须改变角质层的结构和组成，以便在不影响其基本功能的情况下增强某些角质层特性。这一目标只有在彻底了解角质层形成中所涉及的各种生物合成途径的遗传调控的基础上才能实现。以前的研究要么集中在果肉上，忽视了皮肤的重要性，要么专门研究水果角质层的狭窄组成元素。在这个项目中，我们建议调查所有四个重要的生物合成途径相关的番茄果实角质层的形成（蜡，角质，三萜类化合物和黄酮类化合物的生物合成）。 本项目的目标是：a）通过分离表皮特异性基因和参与四个途径关键步骤的启动子来产生操纵番茄果实表皮的分子工具箱; B）产生在目标a中分离的基因中过表达或RNAi沉默的转基因植物; c）在果实表皮超微结构和组成方面对转基因进行表型表征; d）通过测量水势、蒸腾作用、抗裂性、生长和货架期来评估转基因品系的所得果实品质; e）在不同角质层代谢途径改变的转基因品系之间产生杂交，以测试各种组分对表皮性质和果实性状的组合作用。 该项目是三个实验室新成立的合作项目，结合了水果分子遗传学、植物化学、生理学和水果质量评估方面的专业知识。它将提供有关果皮结构和性质的基础知识。此外，它将有助于未来番茄育种系的选择和具有最佳表皮特性的果实的转基因系的产生，从而提高质量。

The skin of fleshy fruits consists of a layer of epidermal cells that are covered with a thick waxy cuticle. The latter is crucial for resistance against pathogens and drought, and for the appearance of the fruit (color, glossiness, texture), the efficacy of post harvest treatments, storage, transport and shelf life. Therefore, it is a very important factor determining fruit quality and, consequently, customer preference. To improve fruit quality, cuticle structure and composition must be altered so that certain cuticle traits are enhanced without impeding its essential functions. This goal can only be reached based on a thorough understanding of the genetic regulation of the various biosynthetic pathways involved in cuticle formation. Previous studies either focused on fruit flesh, ignoring the importance of the skin, or specialized in narrowly selected compositional elements of the fruit cuticle. In this project we propose to investigate all four important biosynthetic pathways relevant for tomato fruit cuticle formation (wax, cutin, triterpenoid and flavonoid biosynthesis).      The objectives of this project are: a) to generate a molecular tool box for manipulating the tomato fruit skin by isolating epidermis-specific genes and promoters involved in key steps of the four pathways; b) to generate transgenic plants overexpressing or RNAi silenced in genes isolated in objective a; c) to phenotypically characterize the transgenics with respect to fruit cuticle ultrastructure and composition; d) to assess the resulting fruit quality of transgenic lines by measuring water potential, transpiration, cracking resistance, growth and shelf life; e) to generate crosses between transgenic lines altered in the different cuticle metabolic pathways in order to test the combined effect of various components on skin properties and fruit traits.      The project is a newly established collaboration of three labs, combining expertise in fruit molecular genetics, phytochemistry, physiology and fruit quality assessment. It will provide fundamental knowledge on fruit skin structure and properties. Moreover, it will assist in the future selection of tomato breeding lines and the generation of transgenic lines with fruit having optimal skin properties and therefore enhanced quality.