Shi Yuan, Pang Xiaoqin, Liu Wenjing, Wang Rui, Su Deding, Gao Yushuo, Wu Mengbo, Deng Wei, Liu Yudong, Li Zhengguo
Key Laboratory of Plant Hormones and Development Regulation of Chongqing, School of Life Sciences, Chongqing University, 401331, Chongqing, China.
Center of Plant Functional Genomics, Institute of Advanced Interdisciplinary Studies, Chongqing University, 401331, Chongqing, China.
Hortic Res. 2021 Dec 1;8(1):259. doi: 10.1038/s41438-021-00696-8.
Chlorophylls and carotenoids are essential and beneficial substances for both plant and human health. Identifying the regulatory network of these pigments is necessary for improving fruit quality. In a previous study, we identified an R2R3-MYB transcription factor, SlMYB72, that plays an important role in chlorophyll and carotenoid metabolism in tomato fruit. Here, we demonstrated that the SlMYB72-interacting protein SlZHD17, which belongs to the zinc-finger homeodomain transcription factor family, also functions in chlorophyll and carotenoid metabolism. Silencing SlZHD17 in tomato improved multiple beneficial agronomic traits, including dwarfism, accelerated flowering, and earlier fruit harvest. More importantly, downregulating SlZHD17 in fruits resulted in larger chloroplasts and a higher chlorophyll content. Dual-luciferase, yeast one-hybrid and electrophoretic mobility shift assays clarified that SlZHD17 regulates the chlorophyll biosynthesis gene SlPOR-B and chloroplast developmental regulator SlTKN2 in a direct manner. Chlorophyll degradation and plastid transformation were also retarded after suppression of SlZHD17 in fruits, which was caused by the inhibition of SlSGR1, a crucial factor in chlorophyll degradation. On the other hand, the expression of the carotenoid biosynthesis genes SlPSY1 and SlZISO was also suppressed and directly regulated by SlZHD17, which induced uneven pigmentation and decreased the lycopene content in fruits with SlZHD17 suppression at the ripe stage. Furthermore, the protein-protein interactions between SlZHD17 and other pigment regulators, including SlARF4, SlBEL11, and SlTAGL1, were also presented. This study provides new insight into the complex pigment regulatory network and provides new options for breeding strategies aiming to improve fruit quality.
叶绿素和类胡萝卜素对植物和人类健康而言都是必不可少的有益物质。识别这些色素的调控网络对于提高果实品质至关重要。在之前的一项研究中，我们鉴定出一个R2R3-MYB转录因子SlMYB72，它在番茄果实的叶绿素和类胡萝卜素代谢中发挥着重要作用。在此，我们证明了与SlMYB72相互作用的蛋白SlZHD17（属于锌指同源结构域转录因子家族）也在叶绿素和类胡萝卜素代谢中发挥作用。在番茄中沉默SlZHD17可改善多种有益农艺性状，包括矮化、开花加速和果实提前收获。更重要的是，下调果实中的SlZHD17会导致叶绿体更大且叶绿素含量更高。双荧光素酶、酵母单杂交和电泳迁移率变动分析表明，SlZHD17直接调控叶绿素生物合成基因SlPOR-B和叶绿体发育调节因子SlTKN2。抑制果实中的SlZHD17后，叶绿素降解和质体转化也受到阻碍，这是由叶绿素降解的关键因子SlSGR1受到抑制所致。另一方面，类胡萝卜素生物合成基因SlPSY1和SlZISO的表达也受到抑制且直接受SlZHD17调控，这导致色素沉着不均，并降低了成熟阶段SlZHD17受到抑制的果实中的番茄红素含量。此外，还展示了SlZHD17与其他色素调节因子之间的蛋白质-蛋白质相互作用，这些因子包括SlARF4、SlBEL11和SlTAGL1。本研究为复杂的色素调控网络提供了新的见解，并为旨在提高果实品质的育种策略提供了新的选择。
