Unveiling UVB resilience in Oryza sativa L.: Integrative analysis of physiological, molecular and microRNA responses

Abstract

Rice is the staple food for more than half of the global population. It is cultivated in over 100 countries, and is predominant in Asia, which accounts for 90 % of the world's production. As the most crucial food crop globally, rice is sensitive to both UVB radiation and climate variations. UltraViolet-B radiation (UVB) is recognised as adverse factors for photosynthesis and plant growth. The current study investigates the resilience of Oryza sativa L. (IR20) seedlings to UVB irradiation, focusing on parameters such as photosynthetic pigment, total sugar, phenolic, total free amino acids, malondialdehyde content, hydrogen peroxide, and antioxidative enzymes. The mRNA expression levels of genes involved in UVB perception, signalling, and response (UVR8, HY5, RLCK, PHT2, and URP) were studied using quantitative RT-PCR (RT-qPCR). Additionally, a computational approach was employed to identify UVB-responsive microRNAs (miRNAs) and their corresponding target mRNAs; which were subsequently validated using stem-loop RT-qPCR and RT-qPCR, respectively. Surprisingly, it was discovered that the H2O2 content in the IR20 cultivar increased in response to UVB irradiation, despite no significant changes observed in lipid peroxidation, chlorophyll, and phenolic content. Additionally, UVB irradiation increases the total sugar content and decreases the entire free amino acid content, while not affecting total protein. The RT-qPCR analysis of mRNA expression reveals that UVB exposure augment the expression of genes related to UVB signal detection (UVR8), signalling (HY5, RLCK, and WRKY), and response (PHT2, CA, and URP). Our findings also suggest that at the post-transcriptional stage, miRNAs expressed upon UVB irradiation are responsible for the significant tolerance of IR20 seedlings to UVB radiation. Overall, the results reveal that IR20 exhibits promise candidate for the development of rice varieties that are both highly productive and resilient to UVB induced stress.

Keywords

• UVB tolerance
• Gene expression
• Anti-oxidative enzymes
• Computational approach
• Stress response