Abstract

Malaysia’s rice production has been inadequate for local consumption and thus requires imported rice from other countries. The growing population and increased demand for rice render the rice food security progressively declining. Additionally, the recent global climate change has led to droughts which further exacerbate rice productivity. The local rice industry lacks the new quality rice varieties that are high-yielding yet drought-resistant. In this regard, the Malaysian Nuclear Agency has generated promising rice mutant lines, ML125-2 and ML82-2. Hence, this study aims to determine the drought resistance of ML125-2 and ML82-2 from the perspective of biochemical and transcriptomic profiles. For biochemical analysis, specific activity of peroxidase and proline content were measured under non-stress (NS) and drought stress (DS) conditions, while the transcriptomic analysis focused on determining differentially expressed genes (DEGs) at false discovery rate ≤ 0.1, P < 0.05 and log₂ fold change ≥ ±1. Gene ontology (GO) enrichment analysis was performed on the DEGs for functional annotation based on the database of Kyoto Encyclopaedia of Genes and Genomes (KEGG). The results obtained were subjected to statistical analysis to identify significant differences at P<0.05. For ML125-2, it manifested insignificant changes in specific activity of peroxidase and proline content between NS and DS conditions. The results for transcriptomic analysis of DEGs revealed stress-related genes were upregulated in ML125-2 during the DS treatment. The GO enrichment analysis further identified enhanced photosynthetic activity from the aspects of biological processes, cellular components and molecular function. As for ML82-2, it presented reduced proline content while with highly elevated peroxidase activity. The transcriptomic profiles and GO enrichment results revealed that, compared with its parents, ML82-2 presented the greatest number of genes whose expression was upregulated in response to drought stress. The results of both ML125-2 and ML82-2 under the DS treatment support the notion of their potent drought resistance. However, further advanced studies on its drought resistance are required, including more indicative biochemical parameters and comparing DS-relevant DEG expression levels with the established ones.