Role of the RBR-type E3 ligase SlRBR860 in photoassmilate accumulation in tomato fruits

Abstract Changes in nutrient demands is important determinant of the flow of cellular metabolites from source to sink tissues, but the underlying molecular mechanisms are poorly understood. Here, we obtained tomato mutant plants with partial albinism through EMS mutagenesis. Despite a significant decrease in chlorophyll and photosynthetic activity, albino tissues grew normally without noticeable developmental retardation. Differentially expressed gene (DEG) analysis between albino and adjacent green tissue showed that genes involved in nutrient transport and protein modification were up-regulated in albino tissues. Among these, SlRBR860 , the most highly ranked DEGs in the protein modification category, is predicted to encode an RBR-type protein possessing three zinc-binding domains. Overexpression of SlRBR860 in tomato plants enhanced vegetative growth. Moreover, soluble sugar and total amino acid contents were increased in fruits of SlRBR860 overexpressing plants. These findings suggest that SlRBR860 function as a positive regulator of photoassimilate accumulation in tomato fruits.