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.

中文翻译：

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SlZHD17参与控制番茄果实中的叶绿素和类胡萝卜素代谢

叶绿素和类胡萝卜素是植物和人类健康必不可少的有益物质。识别这些色素的调控网络对于提高水果质量是必要的。在之前的一项研究中，我们鉴定了一种 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起重要作用。在这里，我们证明了属于锌指同源域转录因子家族的 SlMYB72 相互作用蛋白 SlZHD17 在叶绿素和类胡萝卜素代谢中也起作用。沉默SLZHD17在番茄中改善了多种有益的农艺性状，包括侏儒症、加速开花和更早的果实收获。更重要的是下调SLZHD17在水果中导致更大的叶绿体和更高的叶绿素含量。双荧光素酶、酵母单杂交和电泳迁移率变动分析阐明 SlZHD17 调节叶绿素生物合成基因SlPOR-B和叶绿体发育调节剂SLTKN2以直接的方式。抑制后叶绿素降解和质体转化也被延缓SLZHD17在水果中，这是由于抑制SGR1，叶绿素降解的关键因素。另一方面，类胡萝卜素生物合成基因的表达SLPSY1和斯尔齐索还受到 SlZHD17 的抑制和直接调节，导致色素沉着不均匀，降低果实中的番茄红素含量SLZHD17在成熟阶段压制。此外，还介绍了 SlZHD17 与其他色素调节剂（包括 SlARF4、SlBEL11 和 SlTAGL1）之间的蛋白质-蛋白质相互作用。这项研究为复杂的色素调控网络提供了新的见解，并为旨在提高水果质量的育种策略提供了新的选择。