Genome-Wide Identification of the PIN-LIKES (PILS) Gene Family in Alfalfa (Medicago sativa L.) and Its Expression Analysis Under Abiotic Stresses

The PIN-LIKES (PILS) gene family is crucial for regulating auxin homeostasis and stress adaptation in plants; nevertheless, a comprehensive study on this family in alfalfa (Medicago sativa) remains insufficient. This research found 46 MsPILS genes within the tetraploid alfalfa genome and categorized them into four subfamilies. The genes are irregularly allocated throughout 16 chromosomes, with tandem duplications acting as a primary catalyst for family expansion. Analysis indicated that all MsPILS proteins contain the conserved Mem_trans domain. The promoter study revealed that MsPILS genes had many cis-elements that respond to abiotic stressors and hormones. qRT-PCR research indicated that MsPILS genes exhibit variable expression across several tissues and respond to multiple abiotic stressors. Protein–protein interaction (PPI) research revealed PIN3, PIN5, and PIN6 as principal interacting partners of the MsPILS proteins. Subcellular localization studies indicated that MsPILS1c is in the nucleus, plasma membrane, and endoplasmic reticulum (ER). This research offers significant genetic resources and a theoretical framework for elucidating the activities of PILS genes and for molecular breeding aimed at improving stress tolerance in alfalfa.