Purple acid phosphatases (PAPs) play a significant role in plant phosphorus nutrition and can not only release phosphorus from the soil but also regulate the distribution of phosphorus in plants throughout their entire growth and development process. Moreover, members of the PAP protein family exert a more extensive influence on plant mineral homeostasis, developmental processes, and stress responses. Three clusters of purple acid phosphatases, including 31 putative genes, were identified in apples (Malus domestica) by searching the Genome Database for Rosaceae. The structure, chromosomal distribution and location, phylogeny, motifs, and cis-acting elements in the gene promoter regions of the MdPAP gene family are reviewed. These genes exhibit different expression patterns in different tissues. For example, almost all MdPAP genes are strongly expressed in the roots, except for MdPAP10, MdPAP12, and MdPAP27. Similarily, all MdPAPs were expressed in the leaves while the transcript levels of MdPAP7, MdPAP10, MdPAP15, MdPAP21, MdPAP24, MdPAP26, MdPAP29, and MdPAP30 were highest in apple flowers. Overall, the expression of the 31 genes significantly changed in either the roots or leaves following the application of phosphorus and/or drought stress. These results indicate that MdPAP family members play a role in plant adaptation to adverse environments. This work explores the adaptative responses to phosphorus and/or drought conditions in apple and establishes a foundation for an enhanced comprehension of the evolution of PAP families and the exploration of the genes of interest.

Salt stress significantly constrains plant growth and development, with the root system serving as the primary organ for sensing and responding to salinity. Poplar (Populus spp.), a widely cultivated tree species, plays important roles in urban greening, windbreaks and sand fixation, and various economic sectors. In this study, we conducted a comparative analysis of the salt tolerance of root systems of six different poplar cultivars. Key physiological indicators—including root activity, ion homeostasis, reactive oxygen species (ROS)-scavenging capacity, and nitric oxide (NO) content—were evaluated under saline conditions. Our findings indicate that the salt resistance of the six cultivars follows the order: P. simonii > P. cathayana > P. tremula × P. alba ‘717’ > P. deltoides × P. euramericana ‘Nanlin 895’ > P. deltoides × P. euramericana ‘Bofeng 3’ > P. alba × P. glandulosa ‘84K’. Furthermore, a transcriptomic analysis was performed on the most resilient species, P. simonii. These results reveal that P. simonii primarily orchestrates its salt stress response through the modulation of MAPK cascades and nitrogen metabolism pathways. This research provides theoretical support for elucidating the molecular mechanisms underlying the salt stress response in poplars and offers a foundation for the molecular breeding of salt tolerant poplar varieties.