Fig. 8. Proposed model for SlZHD17 regulation of pigment metabolism in tomato fruit.

Our study uncovers a SlZHD17-regulated network involved in chlorophyll and carotenoid metabolism. The SlMYB72-interacting protein SlZHD17 directly regulates the SlPOR-B gene, which influences chlorophyll biosynthesis. SlZHD17 also regulates SlTKN2 in a direct manner, which determines chloroplast development in tomato fruit. On the other hand, the important regulator of chlorophyll degradation, SlSGR1, and the crucial carotenoid biosynthesis genes SlPSY1 and SlZISO are also directly regulated by SlZHD17. Furthermore, protein–protein interactions between SlZHD17 and other pigment regulators, including SlARF4, SlBEL11, and SlTAGL1, are also presented here. SlTAGL1 interacts with RIN, which is an important regulator of tomato fruit ripening. SlTKN2- and SlARF4-induced chloroplast development was referenced by Nadakuduti et al.¹¹