Expression Characteristics of Hypoxia Adaptation-Associated Genes in Pastor roseus under Different Altitudinal Conditions

Abstract Pastor roseus is a long-distance migratory bird that arrives annually in May at grasshopper-infested steppes of Xinjiang, characterized by a broad altitudinal gradient, for breeding. The dual physiological stressors of high metabolic demand during breeding and high-altitude hypoxia are key selective pressures driving the evolution of hypoxia adaptation in birds. Hypoxia-inducible factor (HIF) is critical for cellular hypoxia responses, and Prolyl hydroxylase 2 (PHD-2) maintains its homeostatic balance. We examined the molecular basis of hypoxia adaptation by measuring HIF-2α, HIF-1β, and PHD-2 expression via qRT-PCR in whole blood of birds sampled across an altitudinal gradient. Results showed: (1) HIF-2α expression was significantly higher at the WQ and XY sites than at the lowest-altitude HC site (P < 0.05). (2) HIF-1β remained relatively stable, being significantly higher at the highest-altitude (XY) site than in the HC and YN groups (P < 0.05), with no significant differences among the other groups. (3) PHD-2 expression was significantly higher in the YN and HM groups than in the lowest-altitude HC group (P < 0.05), with no significant differences among the other groups or between YN and HM. These findings indicate that HIF-2α, HIF-1β, and PHD-2 show distinct but coordinated expression along the altitudinal gradients of P. roseus breeding habitats, suggesting their potential joint involvement in the hypoxic stress response. This contributes to a deeper understanding of the molecular mechanisms underlying high-altitude hypoxia adaptation and provides a theoretical framework for conserving grasshopper natural enemies and investigating the ecological adaptability of migratory avian species.