Understanding the Role of Light Response BTB E3 Ubiquitin Ligases in Temperature-mediated Regulation of Growth and Development in Arabidopsis thaliana

Singhal, Chirag (2025) Understanding the Role of Light Response BTB E3 Ubiquitin Ligases in Temperature-mediated Regulation of Growth and Development in Arabidopsis thaliana. PhD thesis, Indian Institute of Science Education and Research Kolkata.

Text (Phd thesis of Chirag Singhal (17IP001)) 17IP001.pdf - Submitted Version Restricted to Repository staff only Download (7MB)

Abstract

Rising temperatures from global warming are jeopardizing crop yields, threatening food security and future agricultural demands. To combat this, we must curb carbon emissions and delve into the physiological impact of heat on plants to develop temperature-resilient crops. PHYTOCHROME INTERACTING FACTOR 4 is a key regulator that orchestrates the plant’s response to warm ambient temperatures by altering its morphology and architecture, known as thermomorphogenesis. Our research reveals that LIGHT RESPONSE BTBs (LRBs) E3 ubiquitin ligases are crucial for thermos-sensory responses. Transcriptome analysis suggests that lrb123 and pif4 mutants exhibit similar gene expression profiles, suggesting overlapping functions. Through pharmacological assays, LC-MS hormone analysis, and histo-chemical staining, we proved that LRBs are crucial for maintaining auxin homeostasis. Genetic interaction studies revealed that the hypersensitive phenotype of PIF4-overexpression (PIF4-OE) is strongly suppressed in the lrb12 mutant background. At the same time, overexpression of LRB1 or LRB2 further enhances PIF4-OE line growth phenotypes, suggesting that LRBs are essential to promote PIF4 function. We also observed that LRBs interact with negative regulators of PIF4, with phyb partially suppressing the lrb12 short hypocotyl phenotype. Notably, we found that LRBs-mediated promotion of PIF4 function is independent of ELF3. Moreover, we found that the short hypocotyl phenotype of lrb12 is strongly suppressed by hy5, as observed in the lrb12 hy5 triple mutant. Furthermore, we found that LRBs physically interact with HY5 and degrade it via the 26S proteasomal pathway. These results suggest that HY5 is a novel substrate of LRBs for degradation and acts as an essential regulatory mechanism through which LRBs promote themomorphogensis, in addition to promoting PIF4 function likely by inhibiting phyB activity.

Actions (login required)

View Item