Role of BBX proteins in shade avoidance response in Solanum lycopersicum

Abstract

BBX proteins encompass a group of zinc-finger transcription factors that contain at least one conserved B- box domain in their N-terminal region, which play important roles as regulators of flowering, circadian clock, photo and skotomorphogenesis, biotic and abiotic stress responses, and light signaling transduction. Several BBX proteins that regulate shade avoidance have been identified, mostly in Arabidopsis thaliana model species. Shade avoidance response include a series of physiological alterations, such as stem elongation, reduced branching, hyponastic leaf orientation, early flowering and accelerated senescence, collectively termed shade avoidance syndrome (SAS). All these traits determine plant architecture that, in turn, is a key factor for yield. Recently, our research group has identified 31 BBX genes in tomato, Solanum lycopersicum L., and we are exploring their functions in vegetative and reproductive growth, yield and fruit quality. In particular, SlBBX20, the object of study of the candidate's undergraduate fellowship and this BEPE project, has shown to regulate biomass production, flowering time and number, and fruit size and quality. Thus, these results encouraged us to establish the collaboration with Prof. Botto's research group to further explore the role of SlBBX20 in shade avoidance response. So, this project proposes three experimental blocks to evaluate the response of Slbbx20 mutant to shade growing conditions: (i) seedlings under low red/far red light ratio; (ii) plants under low red/far red light ratio and; (iii) plants under high density planting. The improvement of our knowledge about the molecular mechanisms underneath SAS in agronomical important species will allow to design strategies to tailor crop architecture for breeding high-density tolerant crop cultivars. (AU)