Comparative Genomics Analysis of the Populus Epidermal Pattern Factor (EPF) Family Revealed Their Regulatory Effects in Populus euphratica Stomatal Development

Drought stress seriously threatens plant growth. The improvement of plant water use efficiency (WUE) and drought tolerance through stomatal regulation is an effective strategy for coping with water shortages. Epidermal patterning factor (EPF)/EPF-like (EPFL) family proteins regulate stomatal formation and development in plants and thus contribute to plant stress adaptation. Here, our analysis revealed the presence of 14 <i>PeEPF</i> members in the <i>Populus euphratica</i> genome, which exhibited a relatively conserved gene structure with 1-3 introns. Subcellular localisation prediction revealed that 9 <i>PeEPF</i> members were distributed in the chloroplasts of <i>P. euphratica</i>, and 5 were located extracellularly. Phylogenetic analysis indicated that PeEPFs can be divided into three clades, with genes within the same clade revealing a relatively conserved structure. Furthermore, we observed the evolutionary conservation of <i>PeEPFs</i> and <i>AtEPF/EPFLs</i> in certain domains, which suggests their conserved function. The analysis of cis-acting elements suggested the possible involvement of <i>PeEPFs</i> in plant response to multiple hormones. Transcriptomic analysis revealed considerable changes in the expression level of <i>PeEPFs</i> during treatment with polyethylene glycol and abscisic acid. The overexpression of <i>PeEPF2</i> resulted in low stomatal density in transgenetic lines. These findings provide a basis for gaining insights into the function of <i>PeEPFs</i> in response to abiotic stress.