| The hybrid yellow catfish "Huangyou-1" is a hybrid offspring of a combination of common Pelteobagrus fulvidraco(?)selected from third generations and Pelteobagrus vachelli(?)selected from the second generation.It has the advantages of fast growth and mother-like color and strong resistance,etc..It has been approved as new varieties by the National Aquatic Species and Examination Committee in 2018(GS-02-001-2018).This study focuses on the research of the related biology and growth-related genes IGF-2 of the hybrid yellow catfish "Huangyou-1”.It aims to accumulate the biological background knowledge of the hybrid yellow catfish"Huangyou-1" and to provide a certain theoretical basis for the breeding and optimization of the fish.The main results were shown as follows:1.Principal component analysis showed that the main morphological indexes of hybrid yellow catfish can be divided into 6 aspects,i.e.overall frame contour index,fatness and thinness degree,interorbital distance characteristics,head characteristics,tail characteristics and T-shaped structure characteristics of the front part of the body,with the cumulative contribution rate reaching 76.36%.Scatter plot results showed that there were significant differences in body weight between male and female individuals,which was consistent with the results of discriminant analysis.Through stepwise discriminant analysis,the 11 quantitative and 11 standardized traits of 3262-year-old hybrid yellow catfish and 183 3-year-old hybrid yellow catfish were gradually eliminated,and 8 variables of the 2-year-old fish population,and 2 variables of the 3-year-old fish population were respectively established to establish sex discriminant functions.Through data generation back to the equation,the comprehensive accuracy rate of the 2-year-old fish was 87%,and the comprehensive accuracy rate of the 3-year-old fish was 84.2%.T-test results showed that the main difference between male and female hybrid yellow catfish was concentrated on the fatness and outer contour index.Male fish was wider and longer than female fish.The above-mentioned differential traits and discrimination equations of male and female can provide reference methods and theoretical basis for sex identification of hybrid yellow catfish.2.By using RACE technology,the full-length c DNA of the hybrid yellow catfish "Huangyou-1" IGF-2 gene was successfully cloned.The full-length c DNA sequencewas 3664 bp,including an open reading frame of 762 bp,encoding a total of 252 amino acids,251 bp 5?UTR region and 1232 bp 3?UTR region with 28 bp Poly A tail.The amino acid molecular weight predicted by Ex PASy software is 29.17 KDa and the theoretical isoelectric point is 9.55.Amino acid sequence analysis revealed that it contains a 24 amino acid signal peptide,a C conserved domain and a conserved zinc finger structure.The homology comparison showed that the hybrid yellow catfish "Huangyou-1" IGF-2 gene had the highest identity with the female P.fulvidraco.3.The qRT-PCR method was used to analyze the expression of IGF-2 gene in eight kinds of hybrid yellow catfish "Huangyou-1".The sequence is: liver> heart>kidney> muscle> spleen> gill> gut> brain.The IGF-2 gene is expressed in all stages of embryonic development which generally shows an upward trend.Its expression of the gastrula stage is significantly increased compared with the previous developmental stages which will reach a maximum at the somite stage,and returned to a stable stage from the filming stage to the larval stage.4.Direct sequencing was used to analyze the IGF-2 gene of 253 individuals of hybrid yellow catfish "Huangyou-1",and 1 SNP locus was identified(SNPc.118C>T).Then,the correlation analysis between SNP loci and 11 growth traits of hybrid yellow catfish "Huangyou-1".The results showed that SNPc.118C> T was significantly related to the two important growth traits of hybrid yellow catfish "Huangyou-1".Among them,the body length / head length of CC type was significantly higher than that of TT type,and that of CC type was significantly higher than that of TT type.It shows that the body proportion of CC type individuals is higher than the head length,which implies that the meat content is higher.This SNP site can provide an effective marker for the screening of growth dominant groups of hybrid yellow catfish "Huangyou-1". |
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