The PIN Gene Family in Cucumber (Cucumis sativus L.): Genome-Wide Identification and Gene Expression Analysis in Phytohormone and Abiotic Stress Response

The auxin efflux transporter PIN protein plays a crucial role in the asymmetric distribution of auxin on the plasma membrane, influencing the growth and development of plant organs. In this study, we identified nine members of the <i>PIN</i> gene family in the cucumber genome, which could be classified into five phylogenetic groups. These genes have diverse structures but conserved transmembrane domains. Analysis of cis-acting elements in the promoters revealed that <i>CsPINs</i> contain 48 types of cis-acting elements, predominantly light-responsive elements and plant hormone response elements. In addition, PIN proteins may interact with a variety of auxin-related proteins (including auxin response factor, auxin binding protein, mitogen-activated protein kinase PINOID, etc.) to jointly regulate the auxin synthesis and metabolic pathways. We analyzed the expression profiles of <i>PIN</i> genes in 23 tissues of cucumber using the CuGenDB database, and further investigated the expression levels of <i>PIN</i> genes in leaves and roots in response to different abiotic stresses and hormone treatments by qRT-PCR. This study provides a theoretical basis for clarifying the regulatory mechanism of the cucumber <i>PIN</i> gene family during environmental stress processes.