Maize mutants in miR394-regulated genes show improved drought tolerance

Water limitation represents one of the major threats to agricultural production, which often leads to drought stress and results in compromised growth, development and yield of crop species. Drought tolerance has been intensively studied in search of potential targets for molecular approaches to crop improvement. However, drought adaptive traits are complex, and our understanding of the physiological and genetic basis of drought tolerance is still incomplete. The miR394-LCR pathway is a conserved regulatory module shown to participate in several aspects of plant growth and development, including stress response. Here, we characterized the miR394 pathway in maize, which harbours two genetic loci producing an evolutionarily conserved mature zma-miR394 targeting two transcripts coding for F-Box proteins, named hereby ZmLCR1 and ZmLCR2. Arabidopsis plants overexpressing the zma-MIR394B gene showed high tolerance to drought conditions compared to control plants. Moreover, analysis of the growth and development of single and double maize mutant plants in ZmLCR genes indicate that these mutations do not affect plant fitness when they grow in normal watering conditions, but mutants showed better survival than wild-type plants under water deprivation conditions. This increased drought tolerance is based on more efficient intrinsic water use, changes in root architecture and increased epicuticular wax content under water-limiting conditions. Our results indicate that the miR394-regulated ZmLCR genes are involved in drought stress tolerance and are remarkable candidates for maize crop improvement.