Camparative Transcriptomic Analysis Of Brain Expression Differences Between Cave And Surface Sinocyclocheilus Species

Sinocyclocheilu is cavefish.According to its adaptability to the cave,Sinocyclocheilu can be divided into cave type and surface type.Cave is extreme environment that perennial darkness,lack of photosynthesis and nutrients.It is a great challenge to the growth and development of the creatures living in cave.During the long-term evolution,fish living in cave environments had formed many adaptive features,such as loss of vision and pigmentation,craniofacial bone fusions,increased fat storage,reduced sleep,and amplified nonvisual sensory systems.As the most important organ of organisms,brain play an important role in control the growth,development,metabolism,physiological and biochemical processes.Fishes that adapted to different environments also have different regulate ways of their brains.It is unclear what are the differences between the regulate ways of cave and surface type Sinocyclocheilu brain,and what effects these different regulation approaches have on their growth,development and survival.In this study,comparative transcriptome techniques were used to research the brain tissues of cave type and surface type Sinocyclocheilus,so as to explore the main expression differences in brain tissues of Sinocyclocheilus in different environments at the transcriptome level.In this study,the second generation of sequencing technology was used to sequence the brain tissue transcriptome of Sinocyclocheilus,malacopterus(surface species)and Sinocyclocheilu rhinocerous(cave species)to obtain 34.07Gb Clean data,a total of 98,564 Unigenes were obtained,and a total of 20,344 differential expressions genes were screened.Among them,3289 were significantly different,ial expressions genes,2598 of which were significantly down-regulated,accounting for 78.9%of all significantly differential expressions genes,and 691 significantly up-regulated genes accounted for 21.1%of all significantly differential expressions genes.The main results we obtained after analyzing the transcriptome data are:1.There are significantly differences in the expression patterns of surface type S.malacopterus and cave type S.rhinocerous brain genes.(up-regulate and down-regulate)In all significant differential expressions genes,78.9%is S.rhinocerous relative to S.malacopterus down-regulated,and 39.5%of the differential expressions genes were responsible for regulate biological processes.2.The brain plays an important regulation role in the development of the head and eyes morphology and brain structure of the two species of'Sinocyclocheilus.Some genes related to head and eyes morphological development,such as dab1,coasy andpqbpl produced significantly down-regulated in cave type S.rhinocerous brain compared with surface type S.malacopterus.3.The brain plays an important regulation role in the development of retina and lens of the two species of Sinocyclocheilus.Some genes related to normal visual development,such as lens protein gene cryz and retinal development gene cep290 were produced significantly down-regulated in cave type S.rhinocerous brain compared with surface type S.malacopterus.4.The brain has a significantly regulation effect on the circadian rhythm,behavioral patterns and insulin secretion of the two species of Sinocyclocheilu.The expression levels of genes related to insulin secretion,circadian rhythm and behavioral patterns such as cdkl6?mtpn?hdac5?ubrl?ophn1 and faah genes in cave type S.rhinocerous brain were produced significantly down-regulated compared with surface type S.malacopterus.Our results show that the brain of the cave type S.rhinocerous plays an important role in the adaptive evolution process,and is regulated in various ways to make the S.rhinocerous adapt to the extreme cave environment better.