Comprehensive identification of aquaporins under salt stress, and functional characterization of DoTIP1-1 in Dendrobium officinale

Salt stress severely constrains plant growth and productivity, so understanding the underlying mechanisms of salt stress is crucial for the genetic improvement of plants. Aquaporins (AQPs), which facilitate the transport of water or nutrients, exert an indispensable role in plants' response to salt stress. The AQP family in Dendrobium officinale, a commercially important medicinal and edible orchid, has not been identified or functionally characterized, while an understanding of this plant's tolerance to salinity remains unexplored. In this study, a genome-wide identification of AQP genes in D. officinale was performed using a salt-induced transcriptome. The 28 AQP members were mined and classified into four subfamilies (NIPs, PIPs, SIPs, and TIPs), and their physicochemical and bioinformatic properties were analyzed. Overexpression of DoTIP1-1 in D. officinale significantly enhanced salt tolerance via the accumulation of proline and water-soluble polysaccharides that improved water retention. Furthermore, salt tolerance was fortified by the improved activity of antioxidant enzymes (peroxidase and superoxide dismutase), allowing reactive oxygen species to be scavenged, and augmenting photosynthetic efficiency due to the upregulated expression of stress-responsive genes. This study provides the first comprehensive analysis of the AQP family in D. officinale and demonstrates that DoTIP1-1 is a key genetic determinant for enhancing salt tolerance, offering significant potential for the genetic improvement of this plant to resist abiotic stress.