Genome-Wide Identification and Expression Analysis of Thionin Family in Rice (Oryza sativa) and Functional Characterization of OsTHION15 in Drought Stress and ABA Stress

The <i>OsTHION</i> family represents a class of cysteine-rich signal peptides widely recognized for their significant roles in plant disease resistance and immunity. While members of this family are known to be induced under various biotic and abiotic stresses, their responses to environmental stressors beyond disease resistance remain underexplored. This study investigates the evolution, expression patterns, and functional roles of the <i>OsTHION</i> gene family in rice (<i>Oryza sativa</i>) under diverse stress conditions. Using sequence data from the Phytozome database, we identified 44 <i>OsTHION</i> family members and classified them into four groups based on phylogenetic analysis. <i>Cis</i>-acting element analysis revealed that the promoter regions of <i>OsTHION</i> genes are enriched with regulatory elements associated with light response, hormone signaling, plant growth, and stress responses. The <i>OsTHION</i> genes exhibit complex organ-specific expression patterns, with <i>OsTHION30</i> and <i>OsTHION36</i> showing ubiquitous expression, while other members are highly expressed in specific tissues or developmental stages. Under drought, salt, and low-temperature stress, <i>OsTHION</i> genes undergo significant expression changes, underscoring their critical role in plant adaptation to environmental challenges. Notably, <i>OsTHION15</i> was markedly upregulated under drought stress, and the <i>Osthion15</i> mutant displayed heightened sensitivity to drought and ABA stress, confirming its pivotal role in stress resistance. RNA sequencing analysis identified many differentially expressed genes (DEGs), primarily enriched in pathways related to ribosomal function and plant hormone signaling, suggesting that <i>OsTHION15</i> may regulate stress responses through multiple mechanisms. In summary, this study advances our understanding of the <i>OsTHION</i> gene family and highlights its intricate involvement in regulating rice growth, development, and environmental stress responses. These findings offer valuable insights and technical support for crop improvement, with potential applications in enhancing environmental adaptability and yield stability in crops.