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

肉质水果的表皮由一层表皮细胞组成，表皮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，以及水果的外观（颜色，光泽度，质地），收获后处理的功效，储存，运输和保质期至关重要。因此，它是决定水果品质的一个非常重要的因素，因此也决定了顾客的偏好。为了提高果实品质，必须改变果质层的结构和组成，在不影响果质层基本功能的前提下，提高果质层的某些性状。这一目标只有在深入了解角质层形成过程中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，忽视了果皮的重要性，要么专门研究水果角质层的狭窄组成元素。在本项目中，我们建议研究与番茄果实角质层形成相关的所有四种重要生物合成途径（蜡、角质层、三萜和类黄酮的生物合成）。该项目的目标是：a)通过分离参与这四个通路关键步骤的表皮特异性基因和启动子，生成一个操纵番茄果实皮的分子工具箱；b)产生过表达目标a中分离基因或RNAi沉默的转基因植株；C)对转基因果实角质层超微结构和组成进行表型表征；D)通过测定水势、蒸腾、抗裂性、生长和保质期来评价转基因品系的果实品质；E)在不同角质层代谢途径发生改变的转基因系之间产生杂交，以测试各种成分对果皮特性和果实性状的综合影响。该项目是由三个实验室新建立的合作项目，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本知识。此外，它将有助于未来番茄育种品系的选择，并产生具有最佳果皮特性的转基因品种，从而提高品质。

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.