Genome-Wide Identification and Expression Analysis of the Aquaporin Gene Family in the Qinghai Toad-Headed Agama (Phrynocephalus vlangalii) and Responses to Acute Cold Stress

The aquaporin (AQP) gene family plays a critical role in water balance and osmotic regulation, yet its function and regulatory mechanisms in plateau reptiles remain poorly understood. In this study, we systematically identified 10 AQP genes in the Qinghai toad-headed agama (<i>Phrynocephalus vlangalii</i>) based on whole-genome data, and conducted a comprehensive analysis of their physicochemical properties, phylogenetic relationships, conserved domains, gene structures, and expression patterns. The results showed that the AQP genes of <i>P. vlangalii</i> are predicted to localize to the plasma membrane and exhibit significant tissue-specific expression, with the highest levels detected in the kidney and liver. Under low-temperature stress, multiple AQP genes displayed dynamic expression patterns during the stress and recovery phases. Specifically, <i>AQP0</i>, <i>AQP2</i>, and <i>AQP5</i> were persistently downregulated in the liver, kidney, and brain, whereas <i>AQP3</i>, <i>AQP7</i>, and <i>AQP9</i> were initially upregulated during early cold exposure but significantly downregulated during recovery, suggesting their coordinated roles in energy metabolism and water conservation. This study provides evidence supporting the involvement of the AQP gene family in the adaptation of <i>P. vlangalii</i> to the cold and arid plateau environment, providing new insights into the regulatory mechanisms of water metabolism in reptiles.