RESUMEN
KEY MESSAGE: Editing ZmGA20ox3 can achieve the effect similar to applying Cycocel, which can reduce maize plant height and enhance stress resistance. Drought stress, a major plant abiotic stress, is capable of suppressing crop yield performance severely. However, the trade-off between crop drought tolerance and yield performance turns out to be significantly challenging in drought-resistant crop breeding. Several phytohormones [e.g., gibberellin (GA)] have been reported to play a certain role in plant drought response, which also take on critical significance in plant growth and development. In this study, the loss-of-function mutations of GA biosynthesis enzyme ZmGA20ox3 were produced using the CRISPR-Cas9 system in maize. As indicated by the result of 2-year field trials, the above-mentioned mutants displayed semi-dwarfing phenotype with the decrease of GA1, and almost no yield loss was generated compared with wild-type (WT) plants. Interestingly, as revealed by the transcriptome analysis, differential expressed genes (DEGs) were notably enriched in abiotic stress progresses, and biochemical tests indicated the significantly increased ABA, JA, and DIMBOA levels in mutants, suggesting that ZmGA20ox3 may take on vital significance in stress response in maize. The in-depth analysis suggested that the loss function of ZmGA20ox3 can enhance drought tolerance in maize seedling, reduce Anthesis-Silking Interval (ASI) delay while decreasing the yield loss significantly in the field under drought conditions. The results of this study supported that regulating ZmGA20ox3 can improve plant height while enhancing drought resistance in maize, thus serving as a novel method for drought-resistant genetic improvement in maize.
