Pd EPF 1 regulates water‐use efficiency and drought tolerance by modulating stomatal density in poplar

Summary Water deficiency is a critical environmental condition that is seriously reducing global plant production. Improved water‐use efficiency ( WUE ) and drought tolerance are effective strategies to address this problem. In this study, Pd EPF 1 , a member of the EPIDERMAL PATTERNING FACTOR ( EPF ) family, was isolated from the fast‐growing poplar clone NE ‐19 [ Populus nigra × ( Populus deltoides × Populus nigra )]. Significantly, higher Pd EPF 1 levels were detected after induction by dehydration and abscisic acid. To explore the biological functions of Pd EPF 1 , transgenic triploid white poplars ( Populus tomentosa ‘YiXianCiZhu B385’) overexpressing Pd EPF 1 were constructed. Pd EPF 1 overexpression resulted in increased water deficit tolerance and greater WUE . We confirmed that the transgenic lines with greater instantaneous WUE had approximately 30% lower transpiration but equivalent CO 2 assimilation. Lower transpiration was associated with a 28% reduction in abaxial stomatal density. Pd EPF 1 overexpression not only strongly enhanced WUE , but also greatly improved drought tolerance, as measured by the leaf relative water content and water potential, under limited water conditions. In addition, the growth of these ox Pd EPF 1 plants was less adversely affected by reduced water availability than plants with a higher stomatal density, indicating that plants with a low stomatal density may be well suited to grow in water‐scarce environments. Taken together, our data suggest that Pd EPF 1 improves WUE and confers drought tolerance in poplar; thus, it could be used to breed drought‐tolerant plants with increased production under conditions of water deficiency.