The adaptive evolution of visual systems has been observed in many cavefish.However,little is known about the molecular mechanisms underlying these adaptations,which include regressive changes such as eye degeneration...The adaptive evolution of visual systems has been observed in many cavefish.However,little is known about the molecular mechanisms underlying these adaptations,which include regressive changes such as eye degeneration.Here,we analyzed phylogenetic and expression patterns of 6 eye-related genes(crx,foxg1b,opn1sw2,otx2,rho and sox2)in 12 Sinocyclocheilus species from China,including 8 stygobionts and 4 stygophiles,and examined photoreceptor cell morphology of these species.Those eye-degenerated species of Sinocyclocheilus were polyphyletic and showed different degrees of photoreceptor defects in responses to cave environments.The eye loss and degeneration are the result of convergent evolution.Although S.anophthalmus grouped with the eye-normal species,it displayed not only a high degree of eye degeneration but also significant expression differences in eyerelated genes compared with the eye-normal species.The gene foxg1b,which was determined to be under positive selection,might play an important role in the process of eye degeneration in S.anophthalmus based on differential expression.Eye-related gene expression and selection may have contributed to the polyphyly of the cave species.We examined gene expression and duplication in 6 eye-related genes and revealed that these genes displayed considerable diversity in relative expression in Sinocyclocheilus fishes.Otx2 and sox2 were significantly up-regulated in individual cave species,while the other 4 genes(crx,foxg1b,opn1sw2 and rho)were significantly down-regulated.These findings provide a valuable resource for elucidating molecular mechanisms associated with visual system evolution in cavefish.展开更多
基金This work was financially supported by grants from the National Natural Science Foundation of China:NSFC31872218(FWM),NSFC31972868(YHZ)NSFC31372191(FWM),and NSFC31270419(ZSH)+1 种基金Funding agencies had no role in the design,collection,analysis,and interpretation of datain the writing of the manuscript or in the decision to submit the manuscript for publication。
文摘The adaptive evolution of visual systems has been observed in many cavefish.However,little is known about the molecular mechanisms underlying these adaptations,which include regressive changes such as eye degeneration.Here,we analyzed phylogenetic and expression patterns of 6 eye-related genes(crx,foxg1b,opn1sw2,otx2,rho and sox2)in 12 Sinocyclocheilus species from China,including 8 stygobionts and 4 stygophiles,and examined photoreceptor cell morphology of these species.Those eye-degenerated species of Sinocyclocheilus were polyphyletic and showed different degrees of photoreceptor defects in responses to cave environments.The eye loss and degeneration are the result of convergent evolution.Although S.anophthalmus grouped with the eye-normal species,it displayed not only a high degree of eye degeneration but also significant expression differences in eyerelated genes compared with the eye-normal species.The gene foxg1b,which was determined to be under positive selection,might play an important role in the process of eye degeneration in S.anophthalmus based on differential expression.Eye-related gene expression and selection may have contributed to the polyphyly of the cave species.We examined gene expression and duplication in 6 eye-related genes and revealed that these genes displayed considerable diversity in relative expression in Sinocyclocheilus fishes.Otx2 and sox2 were significantly up-regulated in individual cave species,while the other 4 genes(crx,foxg1b,opn1sw2 and rho)were significantly down-regulated.These findings provide a valuable resource for elucidating molecular mechanisms associated with visual system evolution in cavefish.
