Research Projects

Temperature is a critical environmental cue that regulates plant growth and adaptation. Warm ambient temperature promotes plant growth by accelerating vegetative and reproductive transitions while strongly compromising plant immunity, increasing disease frequency and severity. Even a slight increase in temperature of just one degree Celsius (1°C) causes major phenotypic changes in plants (Casal and Balasubramanian, 2019). The projected increase in temperature due to global warming can cause significant damage to crop production and food security at the national and international levels. Identifying the genetic components and unravelling their molecular mechanisms is critical for breeding climate-resilient crop varieties for stable yield and durable resistance in the coming decades. The bHLH transcription factor PHYTOCHROME INTERACTING 4 (PIF4) emerged as a critical positive regulator (Koini et al., 2009; Sun et al., 2012), while the photoreceptor phytochrome B (phyB) acts as a key negative regulator of warm temperature response in plants (Jung et al., 2016). Interestingly, the phyB-PIF4 module is vital in modulating plant immunity in warm temperatures (Gangappa et al., 2017). Moreover, upstream positive regulators of PIF4, such as COP1/DET1/SIZ1, play a crucial role in temperature-mediated regulation of growth and defense responses (Gangappa and Kumar, 2017, 2018; Hammoudi et al., 2018), implying that thermosensory pathway plays a major role in suppressing plant defense responses. The E3 ubiquitin ligases control growth and disease resistance across eukaryotes, including plants (Dubiel et al., 2018). We have identified a group of novel E3 ubiquitin ligases, LIGHT-RESPONSE BRIC-A-BRACK/TRAMTRACK/BROAD (LRB), as critical regulators of thermosensory growth that work upstream to PIF4 (Manuscript to be communicated soon). The LRBs function as adaptor proteins for Cullin–RING class E3 ubiquitin ligases (Deshaies et al., 2009). The lrb triple mutant lrb1 lrb2 lrb3 (lrb123, hereafter) has dwarf and compact rosette phenotypes with short petioles (Figure 1, Please refer to OTD), phenocopying mutants with reduced growth but increased immunity. To explore LRBs role in regulating immunity, we analysed the expression of defense marker genes in wild-type (Col-0) and lrb123 mutant seedlings grown under optimum (22°C) or warm (27°C) temperatures. Our preliminary data suggests that the basal expression of key defense genes showed significant suppression at 27°C than 22°C in Col-0 (Figure 2, please see OTD), while their expression in lrb123 is not only significantly elevated at 22°C but also either maintained or significantly upregulated at 27°C compared to Col-0, suggesting the possible role of LRBs in the regulation of defense gene expression and disease resistance. Using a combination of genetic, genomic and biochemical approaches, we aim to unravel LRBs role in plant immunity and temperature-mediated regulation of growth-defense trade-off in Arabidopsis.