Functional characterization of tomato plants edited for SlBBX20

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. In Arabidopsis thaliana, 32 BBXprotein-encoding loci have been identified, which play important roles as regulators of flowering, circadian clock, photo and skotomorphogenesis, biotic and abiotic stress responses, and light signaling transduction. Recently, our research group has identified 31 BBX genes in tomato, Solanumlycopersicum L. Interestingly, mRNA profiling revealed that the plastid type and developmental stage (i.e. proplastid, chloroplast, or chromoplast) seem to affect the transcript accumulation pattern of SlBBX genes in leaves, hypocotyls, cotyledons, and fruits. Particularly, six genes showed a clear association with either early development or ripening of fruits: SlBBX19 (Solyc01g110370), SlBBX20 (Solyc12g089240), and SlBBX26 (Solyc10g006750) were strongly upregulated upon ripening triggering; while, the amount of SlBBX16 (Solyc12g005750), SlBBX28 (Solyc12g005660)and SlBBX29 (Solyc02g079430) mRNA was higher at green stages of fruit development gradually declining afterward. This expression pattern suggests that these genes may be associated with chloroplast-chromoplast transition, ultimately affecting fruit nutritional quality. Thus, under the hypothesis that proteins containing the B-box domain participate in light signaling regulating tomato vegetative and reproductive development and, eventually, fruit quality, the present work aims to functionally characterize slbbx20 mutant tomato plants produced by CRISPR-Cas9 technology by our research group. (AU)