| Chicken(Gallus gallus)is an important model for the study of avian developmental biology,and the apoptosis of webbed interphalangeal tissue during the embryonic development of terrestrial birds represented by domestic chicken is a classic model for the study of physiological cell death.However,due to the wide variety of birds,there are great differences in the morphology of webbed feet between land birds and waterfowl,therefore,the research on the development of chicken embryo’s webbed feet is not suitable to be used as a reference model for the development of duck and other waterfowl embryos.In this experiment,a total of 1000 chicken and duck eggs were used for morphological comparison by collecting embryos in different stage and describing the differences.It is expected to be helpful to scholars interested in the development of waterfowl and terrestrial webbed feet.CTSO(cathepsin o)gene,with higher expression in the interphalangeal membrane of chicken and duck embryos was screened from the transcriptome data of interphalangeal membrane at stages 31,33 and 34.Through consulting the literature,the gene is a cysteine protease identified from c DNA Library of human breast cancer.Its unique gene structure and chromosomal location make it participate in the process of extracellular matrix degradation.Moreover,studies have shown that the apoptosis of physiological cells in many vertebrate tissues and organs requires the participation of such cysteine protease,which plays a key role in inducing and regulating tissue cell apoptosis.In order to understand whether CTSO gene affects the apoptosis of interphalangeal tissue cells during flipper apoptosis.In this study,the temporal and spatial expression of CTSO gene in the fins of chicken and duck embryos were tested by whole embryo in situ hybridization,and the functional role of CTSO gene in chicken embryo foot morphogenesis was speculated according to the literature evidence.After obtaining the preliminary experimental results,combined with the CTSO gene coding region sequences of 11 vertebrates,including chicken,duck,Xenopus laevis,soft shelled turtle,Homo sapiens,mouse and zebrafish,recorded in the database of the National Biotechnology Information Retrieval Center of the United States,the evolutionary tree was constructed,and the selection pressure of CTSO gene was analyzed by PAML software using branching model.The following results and inferences are obtained in this study: 1 The development of webbed feet in chicken embryo and duck embryo is similar in early embryo(Stage 26-28).Their morphological differences mainly occurred after the 31 st stage of embryonic development,the interphalangeal membrane of chicken hind limbs began to degenerate gradually,and completely disappeared at the 35 th stage to form an independent four toes,while in ducks,only the first interphalangeal membrane degenerated,toe I became an independent toe,and toe II,toe III and toe IV were still connected by complete webs to form webbed feet;2.According to the expression of CTSO gene on the interphalangeal membrane of chicken embryo and duck embryos,it is speculated that CTSO gene participates in the development of bird webbeless feet and plays an important role,and its mechanism needs to be verified by further functional tests;3.According to the results of selection pressure analysis,CTSO gene is relatively conservative in the process of evolution(P = 0.5693282 >0.05).It is inferred that its function in various species is stable and important.The results of this study contribute to the research on the morphological development and evolution of bird hind limbs,provide a functionally important candidate gene CTSO for revealing the mechanism of cell apoptosis in the tissue between the toes of flippers during avian embryonic development,and promote the research on the molecular genetic mechanism of morphological differentiation of hind limbs of different species of poultry. |
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