Chapter 6 220 Table 6.2. Summary of IAA, GA, and BR results in our FR experiments (Chapter 4). IAA GA BR Signaling ↑ ↑ = concentration = Sufficiency to recapitulate FR little full full Necessity yes yes 6.3 DIVERSITY OF SAS AND FR-RESPONSIVE TFS Discovering transcription factors (TFs) important for shade avoidance is crucial for unraveling the intricate regulatory networks in plant responses to varying light conditions. These TFs, previously unknown for SAS could play a vital role as key regulators, influencing adaptive strategies in shade-exposed plants. Moreover, comprehending tissue-specific expression patterns is essential since different plant tissues may exhibit distinct responses to light conditions. The identification and characterization of these TFs with tissue-specific expression brings precision to our understanding of the molecular dynamics underlying the complex phenomenon of shade avoidance. In our study on the conservation and evolution of FR-induced transcription factor genes in tomato, identified in Chapter 3 and followed up in Chapter 5, we focused on Solyc01g090760 (GATA TF), Solyc08g080150 (TCP TF), and Solyc07g053450 (bZIP TF). The conservation of the FR-induced patterns of these TFs within Solanaceae provides insights into their potential roles during SAS. We observed divergence of Solanaceae FR-responsive expression patterns of these TFs from Fabaceae and Brassicaceae. This adds another layer of support to FR-responsive Solanaceae regulatory networks having diverged from e.g. Arabidopsis, and again indicates that translation of results from model organisms to non-closely-related crop species could be challenging and would require more focus on diversifying research strategies towards different plant families. Notably, our findings in Chapter 5 also reveal expression in pith, sometimes exclusively, in response to supplemental FR. This finding might be consistent with a role of pith in stem elongation, but overall, our data are limited by the lack of a direct link between pith function and shade avoidance elongation. We have observed that internode elongation goes together with pith elongation in all of the species we looked at, and that typically transcriptionally inactive pith shows upregulation of these TFs in Solanaceae (summarized in Table 6.2). However, we were unable to establish stronger support for the connection between pith function and shade avoidance.
RkJQdWJsaXNoZXIy MTk4NDMw