SlARF10, an auxin response factor, is involved in chlorophyll and sugar accumulation during tomato fruit development.

The photosynthesis of green tomatoes contributes to fruit growth and carbon economy. The tomato auxin response factor 10 (SIARF10) belongs to the ARF family and is located in nucleus. In this study, we found that SIARF10 was highly expressed in green fruit. Overexpression of SIARF10 in fruit produced a dark-green phenotype whilst knockdown by RNAi produced a light-green phenotype. Autofluorescence and chlorophyll content analyses confirmed the phenotypes, which indicated that SIARF10 plays an important role in chlorophyll accumulation. Overexpression of SIARF10 positively affected photosynthesis in both leaves and fruit. Furthermore, SIARFIO-overexpression lines displayed improved accumulation of starch, fructose, and sucrose in fruit, whilst SIARFIO-RNAi lines showed decreased accumulation of starch and sucrose. Regulation of SIARF10 expression altered the expression of AGPase starch biosynthesis genes. SIARF10 positively regulated the expression of SIGLK1, POR, CBP1, and CBP2, which are related to chlorophyll metabolism and regulation. Electrophoretic mobility shift assays confirmed that SIARF10 directly targets to the SIGLK1 promoter. Our results thus indicate that SIARF10 is involved in chlorophyll accumulation by transcriptional activation of SIGLK1 expression in tomato fruit, and provide insights into the link between auxin signaling, chloroplast activity, and sugar metabolism during tomato fruit development.