Construction of the first high-density genetic map for growth related QTL analysis in Ancherythroculter nigrocauda

Ancherythroculter nigrocauda is a fish endemic to the upper areas of the Changjiang(Yangtze)River in China.Quantitative trait locus(QTL)mapping is a powerful tool to identify potential genes affecting traits of economic importance in domestic animals.In this study,a high-density genetic map was constructed with 5901 single nucleotide polymorphism(SNP)makers by sequencing 92 individual fish from a F1 family using the specific-locus amplified fragment sequencing approach.Initially,48 QTLs for total length,body length,body height,and body weight were identified according to the high density of the genetic map with 24 LGs,a total length of 3839.4 cM,and marker spacing of about 0.82 cM.These QTLs explained 27.1%-49.9%of phenotypic variance.The results of this study suggest that major QTLs are responsible for the growth of A.nigrocauda,and these are potentially useful in comparative genomics research,genome assembly,and marker-assisted breeding programs for this species.

Characterization of stmn1a and genetic effects of a 22-bp Indel in its promoter region of bighead carp Hypophthalmichthys nobilis

Stathmin 1(stmn1)gene,which is involved in the control of cell cycle progression,cell proliferation,differentiation and motility,is a crucial relay in the signal transduction of multiple signaling pathways.Reports on the function of stmn1 in fish are scarce.In this study,the characterization and function of stmn1a gene were explored in an important food fish,namely bighead carp(Hypophthalmichthys nobilis).The bighead carp stmn1a(Hynstmn1a)genomic sequence,which has 2995 bp with an ORF of 447 bp,is evolutionarily conserved in teleost fish.The highest level of expression of Hynstmn1a is in the un-fertilized eggs and spleen of adult bighead carp.The overexpression of Hynstmn1a facilitates cell cycle progression and suppresses apoptosis in EPC cells.In an siRNA assay,disruption of stmn1a in EPC cells resulted in the inhibition of cell cycle progression and promotion of apoptosis.Analysis of promoter activity indicated that an upstream transcription factor(foxo4)regulates Hynstmn1a.Zebrafish mutants with stmn1a knockout by CRISPR/Cas9 exhibited a significant retardation of body length(p<0.05).There was no significant difference in body weight between stmn1a-mutant zebrafish and wildtype(p=0.053).A 22-bp Indel in the promoter region of Hynstmn1a with an observed heterozygosity(Ho)of 0.136 in a bighead carp population(n=191).The polymorphism of this 22-bp Indel genotype is significantly associated with body length(BL),head length(HL)(p<0.05),body weight(BW),head height(HH),and head width(HW)(p<0.01),showing its genetic effects on growth promotion.This study sheds light on the function of stmn1a in fish and demonstrates the potential of the 22-bp Indel of Hynstmn1a as a gene marker when selecting breeding individuals for faster growth and a bigger head of bighead carp in aquaculture.

Genomic polymorphisms at the crhr2 locus improve feed conversion efficiency through alleviation of hypothalamus-pituitary-interrenal axis activity in gibel carp(Carassius gibelio)

Improvement in fish feed conversion efficiency(FCE)is beneficial for sustaining global food fish supplies.Here,we show that a set of polymorphisms at locus of the corticotropin releasing hormone receptor 2(crhr2),which is involved in hypothalamuspituitary-interrenal(HPI)axis signaling,is associated with improved FCE in farmed allogynogenetic gibel carp strain CAS Ⅲ compared with that in the wild gibel carp strain Dongting(DT).This set of polymorphisms downregulates the expression levels of crhr2 mRNA in the brain and pituitary tissues in gibel carp strain CAS Ⅲ compared with those in strain DT.Furthermore,compromised HPI axis signaling is observed in gibel carp strain CAS Ⅲ,such as decreased α-melanocyte stimulating hormone protein levels,plasma cortisol content,and stress responses.Moreover,enhanced activation of protein kinase B/mammalian target of rapamycin complex 1 signaling observed in the muscle tissue of strain CAS Ⅲ in comparison to that in strain DT indicated elevated anabolic metabolism in strain CAS Ⅲ.Thus,these studies demonstrate that the genetic markers associated with compromised HPI axis signaling,such as crhr2,are potentially useful for genetic selection toward improvement in farmed fish growth and FCE,which would reduce fishmeal consumption and thereby indirectly facilitate sustainable fisheries.