The role of tomato B-box MicroProteins in reproductive development

Microproteins (miPs) are single-domain proteins that act as post-translational regulators of protein complexes. In Arabidopsis, two miPs, miP1a and miP1b, are involved in the photoperiodic control of flowering time. These miP1s are members of the BBX family, a group of zinc-finger transcription factors and regulators. miP1a and miP1b actively participate in the Arabidopsis flowering process by mediating the recruitment of CONSTANS (CO) into a repressor complex with TOPLESS (TPL). The interaction of CO with miP1a/b and TPL causes a reduction in the expression of the FLOWERING LOCUS T. SlBBX16 and SlBBX17 are the tomato homologs of miP1b and miP1a, respectively. To study the functional role of these tomato microproteins, we overexpressed them in both tomato (cv MicroTom) and Arabidopsis, focusing on phenotypic analyses during reproductive development. Overexpression of SlBBX16 and SlBBX17 in Arabidopsis had a slight influence on the transition from vegetative to flowering stage. Tomato plants overexpressing SlBBX17 continued to produce flowers for a longer period than wild-type plants. Since there is no evidence in the literature for the presence of an Arabidopsis-like flowering inhibitor complex in tomato, we are testing the interactions of SlBBX16/17 with key known flowering regulators by yeast-two-hybrid analysis.