Genome-wide characterization and drought-responsive expression profiling of plasma membrane intrinsic proteins (PIPs) in Caragana korshinskii.

Plasma membrane intrinsic proteins (PIPs) are an important subfamily of aquaporins that function as membrane channels that facilitate water transport across the plasma membrane in plants. Although the molecular mechanisms of PIPs have been extensively studied in model species, their characteristics and functions remain poorly characterized in Caragana korshinskii. Here, 13 CkPIP genes were identified through genome-wide analysis. CkPIPs were clustered into PIP1 (seven members) and PIP2 (six members) subfamilies. They exhibited conserved physicochemical properties, contained cis-acting elements responsive to abiotic stresses and phytohormones, and showed evidence of segmental duplication under purifying selection. Phylogenetic, structural, and expression analyses (RNA-seq and RT-qPCR) were performed to explore their evolutionary patterns and responses to drought stress. Under drought stress, CkPIPs exhibited tissue-specific expression dynamics: CkPIP1;1, CkPIP1;2, and CkPIP2;2 were prominently upregulated, indicating that they play important roles in drought adaptation. This study expands our understanding of the characteristics of the CkPIP family and provides valuable molecular insights for drought-resistance research and forage improvement.