<p>Drought responses in plants highly depend on the genetic makeup of the used plant material. In this study, the transcriptomic responses of a rice drought-tolerant mutant (MT149) and its wild-type counterpart (cv. Neda) to water deficit was examined, aiming to elucidate the genetic and molecular factors responsible for their differential drought tolerance. In RNAseq assay, the high-quality short reads were mapped to reference genome and then, the differentially expressed genes (DEGs) were determined. 3,682 and 3,615 genes were up- and downregulated in drought-tolerant mutant, while 4,305 and 4,355 genes were up- and downregulated in less-tolerant cultivar Neda. 4,973 genes showed similar significant expression patterns in the two genotypes. A total of 1,380 genes with expression specific to drought-tolerant MT149 under drought stress have also been identified. Downstream analyses showed that 36 out of 66 genes annotated for the photosynthesis-related pathways in plants were differentially expressed under drought, supported with the GO enrichment analysis, indicating the higher sensitiveness of photosynthesis to drought in rice compared to any other basal biological process. Many genes in carbon fixation, carbon metabolism and MAPK signaling pathways also were significantly expressed under drought stress. It was determined that in the later pathway, MPK5 and CML4 are two important genes that along with PP2C30 and five SAPK genes play crucial roles in response to drought stress. Furthermore, it was established that higher expression of Rubisco and ALDP genes in CO₂ fixation/metabolism pathways is necessary for sustaining rice plant growth in stressful condition. The analysis of the transcriptome response to water deficit in the drought-tolerant mutant and wild-type plants contributes significantly to our understanding of the molecular responses of rice plant to water deficit stress, with practical implications for crop improvement and food security.</p>