Mechanism analysis of differential hypoxia tolerance ability among Penaeus vannamei families

This study investigated the mechanisms underlying the adaptation of different Penaeus vannamei families to hypoxia. We identified two hypoxia-tolerant families (HR A/B and HR C/D) and one hypoxia-sensitive family (FG I/J) for further stress testing based on the median lethal time values (LT ₅₀ ) of seven families under various dissolved oxygen conditions. After exposed to hypoxia for 96 h, we measured antioxidant enzyme activity and the levels of key proteins related with low-oxygen in shrimp gill tissues, and assessed gene expression of hypoxia-inducible factor-1α (HIF-1α), cytochrome b-c1 (b-c1), cytochrome c oxidase subunit 5b (COX5b). Our results revealed that hypoxia-tolerant families (HR A/B and HR C/D) had a significantly higher increase in antioxidant enzyme activity compared to the FG I/J family, and the mRNA levels of HIF-1α, COX5b and b-c1 genes increased significantly under different hypoxia levels. Additionally, we performed transcriptomic analysis on the gill tissues from the 1 mg/L treatment group. KEGG pathway analysis revealed that compared with family FG I/J, the hypoxia-tolerant families (HR A/B and HR C/D) were notably enriched in six upregulated pathways, including lysosome function, fatty acid metabolism, fatty acid biosynthesis, oxidative phosphorylation, and cysteine and methionine metabolism. They were also enriched in seven down-regulated pathways, including the C-type lectin receptor signaling pathway, phagosome formation, Toll and Imd signaling pathways, beta-alanine metabolism, tyrosine metabolism, and vitamin B6 metabolism. These findings suggested that hypoxia-tolerant families (HR A/B and HR C/D) possessed significant advantages over hypoxia-sensitive family in terms of antioxidant enzyme activity, energy metabolism, and immune regulation.