| The body color of a fish is determined by the pigment in the body which selectively absorbs light of a specific wavelength and at the same time reflects light of other wavelengths.It is influenced by the number and distribution of pigment cells,and the state of intracellular pigment granules.It will change with the change of growth and environment,including morphological body color change and physiological body color change.The morphological changes of body color include the changes of the amount of pigment cells and granules in the epidermis and the migration of pigment cells.Physiological changes of body color include the aggregation and diffusion of pigment particles,as well as the regulatory mechanism of nerves and hormones.During the process of growth and development,the fish will form a self-protection mechanism called countershading,a circumstance that the body color of its dorsal becomes darker and belly becomes lighter,when the light shines on its skin through water.The formation of camouflage can help fish avoid enemies and improve the rate of success in their own predation.As an exogenous stimulating mitogen,ultra violet is the main stimulus of skin pigmentation that can Significantly promote the formation of camouflage,However,it's still unclear about its specific mechanism at present.Based on the previous studies,this paper further verify the effect of violet light/Ultraviolet on the formation of camouflage of zebrafish.At first,we use CRISPR/cas9 technology to knock out the Short-wavelength-sensitive pigments gene-SWS1 in zebrafish.Obtain the pure zebrafish strain after crossing.Then,set up three control groups and three experimental groups,regulate the intensity of the violet light in the range of 2000±100LUX,irradiate the wild-type and the SWS1-/-strain zebrafish from the dorsum for 100 days.After 60 days and 100 days,30 zebrafishes in each group were taken to count and analyze the melanocytes in the skin of their dorsum and venter.It was found that violet light/Ultraviolet could promote the formation of melanocytes in the dorsum skin of zebrafish through T-test.Then,take three zebrafish from each group and extract the RNA from the dorsal skin,sequenced and analyzed by Illumina transcriptome technology.The significant difference genes and functional categories of the two groups were obtained,and the KEGG pathway related to the production of pigment cells was got through the comparison and enrichment between groups.The total number of genes with difference between the two groups was 856,including 375 down-regulated genes and481 up-regulated genes.Go analysis showed that types of the two groups of differentially expressed genes were mainly concentrated in biological processes such as protein hydrolysis,oxidation-reduction process and so on.KEGG pathways related to pigment cells including PPAR signaling pathway?Pyrimidine metabolism?Cell adhesion molecules?CAMs??Linoleic acid metabolism?Peroxisome?Retinol metabolism?Vitamin digestion and absorption?Phenylalanine,tyrosine and tryptophan biosynthesi?Metabolism of xenobiotics by cytochrome P450?Metabolic pathways.In the above,120 differentially expressed genes were collected,20 were up-regulated and 100 were down regulated,indicating that the absence of SWS1 would affect physiological processes such as retinol metabolism,vitamin digestion and absorption,signal molecule interaction,cell metabolic pathway.Among the down regulated genes,we found members of cytochrome P450,such as CYP1A,cyp2p9,cyp3a65 and so on,as well as RDH12.The studies have shown that they are involved in the oxidative metabolism pathways of retinol and retinal.Finally,the expression POMC?RALDH2?RALDH3 and ASIP1 in the skin of dorsum and venter were compared and analyzed by real-time quantitative PCR.Using?-actin as an internal reference,the results showed that after 100 days of violet light/Ultraviolet irradiation,the expression of RALDH2 in the dorsum of wild-type zebrafish was significantly higher than that in the venter,while that in the venter of homozygous zebrafish was significantly higher than that in the dorsum;the expression of POMC in the dorsum of wild-type zebrafish was significantly higher than that in the venter,while that in the dorsum of homozygous zebrafish was not significantly different.And Compared with the wild-type,the expression of POMC and RALDH2 in the dorsal skin of the homozygous decreased significantly,but there was no significant difference in the expression of both in the venter.The results showed that the knock-out of SWS1function lead to the damage of RALDH2 and POMC gene differential expression level in the original dorsal and venter.In addition,in this study,it was found that SWS1knockout did not affect the expression difference of RALDH3 and ASIP1To sum up,violet light/ultraviolet can promote the formation of melanocytes in zebrafish dorsal skin through SWS1 gene.When the SWS1 gene was knockout,some genes related to the synthesis and expression of retinoic acid,such as the members of cytochrome P450 family,retinol dehydrogenase 12 and so on were decreased.At the same time,violet light/ultraviolet can significantly affect the expression of RALDH2in zebrafish skin through SWS1 gene,and then affect POMC,so as to regulate the synthesis of melanocytes. |
PDF Full Text Request