Tomato (Solanum lycopersicum L.) is an important source of nutraceutical compounds for human diet, many of which are totally or partially synthesized in the plastids (e.g. carotenoids and tocopherols). During ripening, the fruits suffer remarkable physiological and biochemical changes associated with chloroplast-to-chromoplast conversion. Phytochrome-mediated light signal transduction regulates plastid biogenesis and maturation, modulate sugar metabolism in early developing fruits and control carotenoids and tocopherol biosynthesis during fruit ripening. BBX proteins are transcription factors (TFs) that have been recently identified as new players in light signaling cascade. They are particularly interesting to explore in tomato due to their putative effect on plastid biogenesis and function and, consequently, their impact on crop quality. Four members of the BBX gene family show a clear ripening associated mRNA accumulation profile: SlBBX20 (Solyc12g089240), SlBBX26 (Solyc10g006750), SlBBX28 (Solyc12g005660) and SlBBX29 (Solyc02g079430). Interestingly, the promoter regions of these four genes show binding motifs for major light signal TFs, such as ELONGATED HYPOCOTYL 5 (HY5) and PHYTOCHROME INTERACTING FACTORS (PIFs). This work hypothesizes that the BBX proteins participate in light signaling physically interacting with different TFs and, ultimately, affecting vegetative and reproductive development. To better understand SlBBX mode of action, this project aims to determine the interactome of these four SlBBX protein encoding genes, whose mRNA profile increase (SlBBX20 and SlBBX26) or decrease (SlBBX28 and SlBBX29) along with tomato fruit development and ripening. To achieve this objective, this study will: (i) identify proteins that interact with the four SlBBX proteins through yeast two-hybrid sequencing (Y2H-seq); (ii) identify proteins that interact with the four SlBBX gene promoters using yeast one-hybrid sequencing (Y1H-seq) and; (iii) and validate the identified SlBBX interactors.
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