Summary NF‐Y transcription factors are reported to play diverse roles in a wide range of biological processes in plants. However, only a few active NF‐Y complexes are known in plants and the precise functions of NF‐Y complexes in flavonoid biosynthesis have not been determined. Using various molecular, genetic and biochemical approaches, we found that NF‐YB8a, NF‐YB8b and NF‐YB8c – a NF‐YB subgroup – can interact with a specific subgroup of NF‐YC and then recruit either of two distinct NF‐YAs to form NF‐Y complexes that bind the CCAAT element in the CHS1 promoter. Furthermore, suppressing the expression of particular NF‐YB genes increased the levels of H3K27me3 at the CHS1 locus and significantly suppressed the expression of CHS1 during tomato fruit ripening, which led to the development of pink‐coloured fruit with colourless peels. Altogether, by demonstrating that NF‐Y transcription factors play essential roles in flavonoid biosynthesis and by providing significant molecular insight into the regulatory mechanisms that drive the development of pink‐coloured tomato fruit, we provide a major advance to our fundamental knowledge and information that has considerable practical value for horticulture.

Growth-regulating factors-interacting factor (GIF) proteins play crucial roles in the regulation of plant growth and development. However, the molecular mechanism of GIF proteins in tomato is poorly understood. Here, four SlGIF genes (named SlGRF1a, SlGIF1b, SlGIF2, and SlGIF3) were identified from the tomato genome and clustered into two major clades by phylogenetic analysis. The gene structure and motif pattern analyses showed similar exon/intron patterns and motif organizations in all the SlGIFs. We identified 33 cis-acting regulatory elements (CAREs) in the promoter regions of the SlGIFs. The expression profiling revealed the four GIFs are expressed in various tissues and stages of fruit development and induced by phytohormones (IAA and GA). The subcellular localization assays showed all four GIFs were located in nucleus. The yeast two-hybrid assay indicated various growth-regulating factors (SlGRFs) proteins interacted with the four SlGIF proteins. However, SlGRF4 was a common interactor with the SlGIF proteins. Moreover, a higher co-expression relationship was shown between three SlGIF genes and five SlGRF genes. The protein association network analysis found a chromodomain helicase DNA-binding protein (CHD) and an actin-like protein to be associated with the four SlGIF proteins. Overall, these results will improve our understanding of the potential functions of GIF genes and act as a base for further functional studies on GIFs in tomato growth and development.

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Background CONSTANS (CO) and CONSTANS-LIKE (COL) transcription factors have been known to regulate a series of cellular processes including the transition from the vegetative growth to flower development in plants. However, their role in regulating fruit yield in tomato is poorly understood. Result In this study, the tomato ortholog of Arabidopsis CONSTANS, SlCOL1, was shown to play key roles in the control of flower development and fruit yield. Suppression of SlCOL1 expression in tomato was found to lead to promotion of flower and fruit development, resulting in increased tomato fruit yield. On the contrary, overexpression of SlCOL1 disturbed flower and fruit development, and significantly reduced tomato fruit yield. Genetic and biochemical evidence indicated that SlCOL1 controls inflorescence development by directly binding to the promoter region of tomato inflorescence-associated gene SINGLE-FLOWER TRUSS (SFT) and negatively regulating its expression. Additionally, we found that SlCOL1 can also negatively regulate fruit size in tomato. Conclusions Tomato SlCOL1 binds to the promoter of the SFT gene, down-regulates its expression, and plays a key role in reducing the fruit size.