Skin Transcriptome On Plumage Color Change Of The Crested Ibis During Breeding Season

The crested ibis(Nipponia nippon)is a kind of rare bird,once widely distributed in Northeast Asia.In the 1980 s,the species was on the verge of extinction due to habitat reduction,food shortage and human hunting.At present,there are only a few captive populations and the problems of low fertilization rate and low survival rate in artificial reproduction also restrict the reconstruction of wild populations.Therefore,it is necessary to strengthen the research on reproduction of the crested ibis.The crested ibis has a unique way of moulting.During the breeding season,the species use water bath to smear their feathers with black substances secreted by the black skin of their neck,thus turning white non-breeding plumage into gray breeding plumage.Studying the molecular mechanism involved in this process can help us further understand the physiological activities of the crested ibis during reproductive period,which could provide theoretical guidance for the artificial breeding of this species.In this study,we collected black skin samples of different individuals of the crested ibis from Tashui Town,Shawan District,Leshan City,Sichuan Province during non-breeding season and breeding season.By comparing the gene expression pattern between two different periods with transcriptome sequencing,we try to find key genes related to plumage color change of the crested ibis during breeding season.Main results are shown as below:(1)Based on the newly acquired transcriptome datasets,we predicted 2359 novel proteincoding genes and formed a new set of 19435 genes of which 1408 genes were actively expressed genes.(2)Analysis of gene expression at the global level revealed that 382 genes were upregulated and 136 genes were down-regulated in skins during non-breeding season compared with those in skins during breeding season.(3)Hierarchical cluster analysis of differentially expressed genes showed that some genes were enriched in tyrosine metabolism pathway and melanogenesis pathway.(4)GO enrichment analysis of differentially expressed genes showed that the downregulated GO terms in skins during non-breeding season were mainly involved in phospholipid metabolism and lipid metabolism while the up-regulated GO terms were mainly related to cytoskeleton and the transport of substances on nuclear membrane.(5)KEGG pathway analysis of differentially expressed genes showed that the expression levels of TYR,TYRP1,DCT and PLA2 in skins during non-breeding season were significantly lower than those in skins during breeding season.Among these genes,the first three are important components of melanogenesis pathway,while PLA2 is related to gonadotropinreleasing hormone pathway.(6)According to the conservative regulatory network of differentially expressed genes in other animals,we predicted the molecular signal map affecting plumage color change of the crested ibis during breeding season.This study preliminarily explored the molecular regulation mechanism of plumage color change of the crested ibis during breeding season,which will contribute to further research in the future and provide a theoretical reference for the protection of this species.