Publication:

Root acclimation of rice exposed to alternate and continuous drought stress

Drought conditions as a result of climate change have detrimentally reduced rice production with roots playing a pivotal role in water uptake and providing valuable insights into adaptation to water scarcity through their anatomical phenotype. Thus, this study aimed to elucidate how drought stress affects the agronomic traits, root anatomical phenotype and identify the differentially expressed genes (DEGs) correspond to drought tolerance. Six rice varieties, Moroberekan, MR297, Apami, Merah Wangi, Biris, and Nona Manis, were grown and subjected to normal watering, alternating two cycles of drought and continuous drought. A preliminary study was conducted to evaluate agronomic traits. Anatomical study was done with the root samples harvested at panicle initiation. Following the findings from morphological and histological study, the RNA from the roots of MR297 and Merah Wangi were then selected for comprehensive transcriptomic analysis using next generation sequencing (NGS). Based on the agronomic analysis, Merah Wangi produced the highest grain yield under both drought stress, followed by Nona Manis and MR297. The results for root phenotype showed great plasticity among the varieties. Under alternating drought stress, Moroberekan had the highest values for anatomical root area, root diameter, stele area, cortex area and metaxylem traits, followed by Merah Wangi. Despite severe drought stress, Merah Wangi exhibited the highest grain yield with better root anatomical structure. Meanwhile, transcriptome analysis of Merah Wangi against MR297 unveiled 35257 and 77115 DEGs responsive to alternate drought and continuous drought stress, respectively. The study revealed an abundance of DEGs in Merah Wangi, with more genes downregulated than upregulated, especially under both drought stress. Significantly, the expression of DEEPER ROOTING 1 and enrichment of DEGs in pathways associated with 'plant hormone signal transduction' and 'metabolite synthesis' underscores their potential relevance to the mechanism underlying drought tolerance in Merah Wangi. The continuous drought stress has triggered the upregulation of hormone related genes, particularly auxin, and cytokinin. In conclusion, Merah Wangi exhibited the highest drought resilience among the varieties studied, a trait attributed to its superior agronomic characteristics, root anatomical phenotypes, and the activation of genes associated with drought response. The findings provide key insights into root acclimation, paving the way for developing more resilient rice varieties under drought stress.