NATARAJA KARABA N.SHRIDHAR, S.2023-05-112023-05-112023-03-29Th-13637https://krishikosh.egranth.ac.in/handle/1/5810197253Mulberry (Morus spp.) is a perennial tree system economically cultivated for its foliage production. To improve foliage production and the sustainability of the sericulture industry, achieving early and rapid bud break is essential. However, the molecular mechanism regulating bud break in mulberry is not well understood. Therefore, this study aimed to identify genes involved in regulating the mechanism of bud break in mulberry. Over fifty genes belonging to key pathways in bud break were selected from a previously generated transcriptome, and their relevance was assessed through in-silico expression analysis using e- northern expression browser available at the Botany Array Resource (BAR) platform. Further, in-vivo expression analysis was carried out using qRT-PCR for 19 genes representing multiple pathways at different time intervals post-induction of bud break. Expression analysis showed that mulberry bud break is tightly controlled by phytohormones, symplastic connectivity, cell cycle and redox signalling. Key genes such as GA signalling genes, symplastic connectivity restoration genes, branching signal integrator genes, and sugar transporter genes were significantly upregulated post-induction of bud break, indicating their positive role in bud burst. In contrast, genes linked to ABA signalling and perception, strigolactone signalling, MADS-box family, and antioxidant-system-linked genes were significantly downregulated post-bud break induction. Further, two uncharacterized genes, DUF1068-like and RRM-like, were functionally validated using post-transcriptional gene silencing (PTGS) by virus-induced gene silencing (VIGS) assay using tobacco rattle virus-based gene silencing vector in Nicotiana benthamiana for their role in growth and development. Silencing of both RRM and DUF1068 resulted in increased axillary bud break and branching, indicating their crucial role in bud growth and development. Overall, the study provided new insights into the molecular mechanisms underlying bud break in mulberry and highlighted the importance of various regulatory pathways involved in this process.EnglishThesis