Chapter 1 24 Chapter 2 of this thesis is a comprehensive phenotyping analysis of two tomato cultivars under different lighting- white light control and white light that is supplemented with far-red light as the treatment. We report various phenotypic traits, including stem and petiole length, leaf area, leaf thickness, chlorophyll content, and cellular level analysis of stem morphology using microscopy. These detailed phenotyping data form the basis for further investigations at the molecular level, focusing specifically on internode 1. Building upon the phenotypic findings, in Chapter 3 we delve into a molecular analysis of internode 1 using time series transcriptomics. This approach allowed for a deeper understanding of the regulatory pathways involved in early-stage elongation, preceding visible changes in plant growth. By examining gene expression patterns over time, we identified several intriguing transcription factors (TFs) including a bZIP finger TF, a GATA TF, and a TCP (TEOSINTE BRANCHED1/CYCLOIDEA/PROLIFERATING) TF for further exploration. In Chapter 4, we unravel the roles of auxin, gibberellin and brassinosteroids in the tomato SAS. Manipulating hormone levels, we aimed to further understand the elongation and cellular changes observed under far-red enrichment. A better understanding of their contribution to SAS was obtained, shedding light on the molecular mechanisms underlying tomato responses to shading. Expanding the investigation outwards in Chapter 5, our study broadened its scope to include multiple dicot species. We aimed to investigate the conservation of pith cell responses in SAS and the conservation of FR-responsiveness of our target TFs across different plants, providing insights into the evolution of this adaptive response. Chapter 6 then brings the discoveries in the experimental chapters together for a general discussion. Through a multidisciplinary approach encompassing phenotyping, transcriptomic analysis, hormone manipulation, and cross-species comparisons, this research thesis unravels the intricate mechanisms of shade avoidance responses in dicots beyond the usual model plant Arabidopsis. Here, we have discussed the rationale behind choosing tomato as the focal point of investigation. This choice may be underscored by the unique characteristics of tomato growth patterns and responses that deviate from established models, thus warranting dedicated exploration. Moreover, the experimental design should be contextualized within the existing gaps in knowledge, emphasizing what remains unknown, particularly in the context of the role of hormones in SAS tomato shade avoidance.
RkJQdWJsaXNoZXIy MTk4NDMw