Auxin homeostasis in plant organ responses to high temperature
Abstract
The life of a plant is a permanent response to environmental stimuli. Plants monitor and constantly integrate the environmental fluctuations in order to adjust their growth and development. Plant hormones are central to these adaptive growth responses. Auxin is a major plant hormone that mediates a plethora of developmental responses in a concentration-dependent manner. Importantly, auxin mediates high temperature (HT)-related responses in root, shoot, and during reproductive development. PHYTOCHROME INTERACTING FACTOR 4 (PIF4) mediates auxin-dependent hypocotyl or petioles elongation to HT. In contrast, root response to HT is independent of PIF4 and hence the impact of auxin to HT-induced root growth is controversial. Similarly, the role of auxin in regulating female floral organ development under HT has not yet been thoroughly investigated. Facing the consequences of global warming, plant growth response to HT is a timely, fundamental research topic with additional potential for applied research fields. Thus, in this research, I propose to investigate the auxin-based mechanisms regulating plant organ response to HT. I present here preliminary results and propose further experiments, covering two research directions: -The first part (A) is the continuation of my submitted (preprinted) manuscript that revealed the role of PILS6 in auxin-dependent root growth under HT. I propose in this part that the transcription factor SPATULA (SPT) is involved in this and aim to investigate how HT impacts on this SPT-PILS6 module to regulate nuclear auxin signalling during root growth. This research will clarify some controversy in the literature and will enable me to dissect whether the hypocotyl (PIF4-dependent) and roots (SPT-dependent) underlie distinct auxin-dependent mechanisms. -The second part (B) will assess how PILS-dependent intracellular auxin signalling affects female flower organ development and productivity under HT conditions. This research will advance the mechanistic understanding of female floral organ development, the pollen-pistil interaction, and the potential role of auxin to regulate these developmental aspects under HT condition. My research direction will fill eminent knowledge gaps and solve some controversy in our understanding of auxin-mediated thermo-responses. This project will contribute to several research fields, connecting temperature sensing, intracellular auxin transport and plant adaptive growth under HT. Overall, my results will further our understanding of how plants respond to HT.