| Summary: | Drought is one of the most prevalent environmental stresses that affect plant growth and development. Improvement in drought tolerance is associated with reduced stomatal density and higher water use efficiency (WUE). In this study, an epidermal patterning factor (EPF), PdEPF3, from a fast-growing poplar clone, NE-19 [Populus nigra × (Populus deltoides × Populus nigra)], was characterized. Quantitative reverse transcription polymerase chain reaction showed that the transcription of PdEPF3 was induced by drought. We further found that the transgenic Arabidopsis overexpressing PdEPF3 had an earlier seedling germination and longer primary roots under osmotic stress treatments, compared with the WT and mutant epf1-1. In addition, ectopic overexpression of PdEPF3 in Arabidopsis plants was able to enhance drought tolerance. This observation was associated with the reduced stomatal density of transgenic plants, which would limit transpiration and reduce water loss, consequently improving the WUE of plants. Interestingly, the reduction of stomatal density in transgenic plants overexpressing PdEPF3 did not affect their photosynthetic capacity. These results indicate that PdEPF3 could be used in transgenic breeding to enhance plant drought tolerance.
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