Enhancing Coleoptile Length of Rice Seeds under Submergence through NAL11 Knockout

Submergence stress challenges direct seeding in rice cultivation. In this study, we identified a heat shock protein, <i>NAL11</i>, with a DnaJ domain, which can regulate the length of rice coleoptiles under flooded conditions. Through bioinformatics analyses, we identified <i>cis</i>-regulatory elements in its promoter, making it responsive to abiotic stresses, such as hypoxia or anoxia. Expression of <i>NAL11</i> was higher in the basal regions of shoots and coleoptiles during flooding. <i>NAL11</i> 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, <i>NAL11</i> 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 <i>NAL11</i> mediated the gluconeogenic pathway, essential for the energy needed in cell expansion. Furthermore, <i>NAL11</i> 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 <i>NAL11</i> 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.