Enhancing Coleoptile Length of Rice Seeds under Submergence through Knockout.

Submergence stress challenges direct seeding in rice cultivation. In this study, we identified a heat shock protein, , with a DnaJ domain, which can regulate the length of rice coleoptiles under flooded conditions. Through bioinformatics analyses, we identified -regulatory elements in its promoter, making it responsive to abiotic stresses, such as hypoxia or anoxia. Expression of was higher in the basal regions of shoots and coleoptiles during flooding. knockout triggered the rapid accumulation of abscisic acid (ABA) and reduction of Gibberellin (GA), stimulating rice coleoptile elongation and contributes to flooding stress management. In addition, mutants were found to be more sensitive to ABA treatments. Such knockout lines exhibited enhanced cell elongation for coleoptile extension. Quantitative RT-PCR analysis revealed that mediated the gluconeogenic pathway, essential for the energy needed in cell expansion. Furthermore, mutants reduced the accumulation of reactive oxygen species (ROS) and malondialdehyde under submerged stress, attributed to an improved antioxidant enzyme system compared to the wild-type. In conclusion, our findings underscore the pivotal role of knockout in enhancing the tolerance of rice to submergence stress by elucidating its mechanisms. This insight offers a new strategy for improving resilience against flooding in rice cultivation.