Executive Summary : | Thermomorphogenesis, i.e., the effect of ambient temperature on plant growth and development, although enormously dissected out in Arabidopsis, remains unexplored in monocots, especially Rice. One breakthrough discovery was the identification of phytochrome interacting factor 4 (PIF4) as the central signaling hub that integrates environmental cues, including light and temperature, to regulate growth and development in Arabidopsis (Xu, 2018). However, no such central regulatory molecules could be identified in the case of Rice. Although noted in Rice, proteins such as PIF-like (PIL) proteins remain to be functionally characterized. The best-established temperature sensor, i.e., phytochrome B (PhyB), has been observed to act through a PIF4-dependent pathway in Arabidopsis (Jung et al., 2016). In response to temperature, plant architectural adaptations and flowering are mediated through PIF4 (Koini et al., 2009; Kumar et al., 2012). Few other proteins in the thermomorphogenic signaling cascade, DET1 and COP1, have been proposed to control thermosensory growth by transcriptional regulation of PIF4 either through HY5 protein or independently (Delker et al., 2014; Gangappa and Kumar, 2017). Another group of authors reported a PIF4-independent pathway originating from TOT3/MAP4K thermosensor in Arabidopsis and Wheat (Dai Vu et al., 2021). These pathways converge in the synthesis of growth hormones, viz. auxin, brassinosteroids, etc., through transcriptional activation by PIF4. This thermomorphogenic cascade is yet to be characterized in Rice plants-one of the most economically important food crops challenged by global warming. A global increase of 1 °C reduced Rice yield by an average of 3.2 ± 3.7%, which in the case of India, shows a larger impacts-6.6 ± 3.8% per °C (Zhao et al., 2017).
Moreover, a higher temperature is associated with greater disease severity, owing to the breakdown of plant disease resistance through altered resistance gene efficacy (Webb et al., 2010). Therefore, using Rice as a model, this project aims to determine the mechanistic basis of thermomorphogenic regulation of growth and development in Rice, especially the critical thermomorphogenic regulators involved. This project firstly intends to identify Rice cultivars with the ability for thermomorphogenesis, followed by a detailed insight into its molecular basis. Since these pathways are enigmatic to date, the key questions include what architectural and anatomical adaptations are induced in response to warm ambient temperature and which key proteins participate in the thermomorphogenic cascade in Rice plants. If any PIF4-like central regulatory node exists, how do these proteins interact to form the thermomorphogenic regulatory network in Rice? Hence, this study shall better understand thermomorphogenesis to generate climate-smart Rice plants for sustainable agriculture in a world challenged by global warming and threatened food security. |