The high-quality genome of Bellamya aeruginosa reveals the molecular mechanisms underlying its remarkable stress resistance.

Abstract

Background: Bellamya aeruginosa belongs to the family Viviparidae and is widely distributed in freshwater ecosystems in Asia. This species is resilient to thermal stress and can survive in polluted waters and consequently has been widely studied as a sentinel species for assessing ecosystem risk. To gain resources to study how B. aeruginosa adapts to harsh environments at the molecular level, we assembled a high-quality genome of this species and compared responses in transcriptome sequencing following exposure to wastewater, heat stress, and cold stress.

Results: We assembled a pseudo-chromosome genome for B. aeruginosa (1.2 Gb, 8 chromosomes) through the integration of multiple sequencing strategies. Comparative genomic analyses demonstrated that genes for the expansion of the Viviparidae branch comprising Cipangopaludina cathayensis, Bellamya purificata, and B. aeruginosa were enriched in GO terms such as developmental growth involved in morphogenesis, regulation of animal organ morphogenesis, and regulation of embryonic development. This may be related to the pattern of viviparous reproduction in viviparids. Transcriptomic analyses revealed that this organism relies on lipid metabolism regulation and antioxidant systems to adapt to hypoxic stresses imposed by wastewater. Additionally, we identified multiple genes encoding heat shock proteins (Hsps) among differentially expressed genes resulting from temperature stress treatments, suggesting that the heat shock response plays a crucial role in enabling B. aeruginosa to cope with environmental stress. In light of these observations, we conducted a comprehensive identification and analysis of the Hsp gene family within B. aeruginosa, discovering that the number of Hsp20 family members was significantly higher in this species compared to other closely related organisms-corresponding with our previous analyses regarding gene family expansion and contraction.

Conclusions: This study has yielded a high-quality genome of B. aeruginosa and provided insights into the potential molecular mechanisms that underpin the organism's environmental resilience, and that Hsps in this species are sensitive to environmental stresses and play a key role in its stress mechanisms.