Transcriptional and post-translational regulation of the photoperiodic flowering pathway in tomato and its interaction with gibberellin and age pathways

Abstract

Distinct environments and latitudes limited human agricultural activities due to the photoperiodic response and its strong impact on flowering time and yield of crops. The CONSTANS (CO) gene is the central regulatory hub in the photoperiodic pathway his several species. In Arabidopsis, CO was identified as a transcriptional activator of the flowering-associated phloem-mobile protein named FLOWERING LOCUS T (FT). Although cultivated tomato (Solanum lycopersicum) is considered a neutral day plant, its wild relative species show a drastic delay in flowering under long day conditions, which was associated with the activity of SELF-PRUNING 5G (SP5G). SP5G represses the expression of the tomato FT homolog, SINGLE FLOWER TRUSS (SFT). We then hypothesized that tomato CONSTANS1 (CO1) positively regulates SP5G transcription under long days, which has been confirmed by our molecular and functional data. However, it is still unknown whether the activation of SP5G by CO1 is direct or indirect, as well as the role and post-translational regulation of CO1 protein. Our experiments suggest that photoperiodic pathway is negatively and positively regulated by DELLA and PHYTOCHROME B1 (PHYB1) proteins, respectively. In this context, this proposal aims to evaluate the direct activation of the SP5G gene by CO1, and the possible CO1 interaction with PROCERA and PHYB1 proteins, since both proteins post- translationally regulate CO activity in Arabidopsis. Additionally, the role of CO1 in tomato will be analyzed through characterization of CO1 mutant (e.g., co1CRISPR) and overexpression transgenic plants (e.g., p35S::CO1), already generated by our research group. Another goal is to identify common target genes among photoperiodic, gibberellin (GA) and age (miR156/SPLs) flowering pathways. For this, we will analyze transcriptomes from vegetative meristems in key genotypes of each pathway (photoperiodic, gibberellin and age). Understanding the photoperiodic responses and its interaction with gibberellin and age flowering pathways may be an important tool to guide tomato and other crops breeding programs. (AU)