Genome-Wide Characterization of the Hyaluronidase Gene Family and Their Potential Roles in Viviparous Black Rockfish(Sebastes schlegeli)

Black rockfish(Sebastes schlegelii)has evolved viviparous reproduction mode.Different from the oviparous fishes,the spermatozoa of black rockfish are stored on the surface of ovarian follicle for over four months until the egg mature in ovary,while the adaptive evolution of fertilization-related genes remains to be studied.In the present study,based on the genome and transcriptome information of black rockfish,a total of 10 hyaluronidase genes were identified by phylogenetic and sequence analyses,including hyal1,hyal2,hyal3,hyal4,hyal6 and spam1a,spam1b,spam1c and spam1d.The spam1 subfamilies,including spam1a,spam1b,spam1c and spam1d,were significantly expanded compared to other species.The adaptive evolution of hyaluronidase was further investigated by selection pressure analysis of branch model and branch site model.The results showed that only spam1 subfamily was positively selected with a large number of positive selection sites,and the evolution rate was significantly higher thanthose of other teleosts.Two positively selected sites,LYS-171 and GLY-164,were located in the neutral hyaluronidase activity domain,which was pivotal for SPAM1 to participate in enzymatic hydrolysis of the extracellular hyaluronic acid matrix and mediate acrosome reaction in mammals.Furthermore,spam1 was mainly expressed in spermatocytes,secondary spermatocytes,and spermatids of testis,whereas it was not found in metamorphic sperm and mature sperm based on the spatiotemporal expression analysis.All results indicated that spam1 might originate from the testis and might be an adaptation of viviparous trait in black rockfish.

Isolation and phylogenetic analysis of feline calicivirus strains from various region of China

Feline calicivirus(FCV)is an important feline pathogen mainly causing upper respiratory tract disease,conjunctivitis,and stomatitis,and it is classifed into genotype I and genotype II.To investigate the prevalence and molecular characteristics of FCV,this study collected 337 cat swab samples from animal hospitals in diferent regions of China from 2019 to 2021.The positive detection rate of FCV was 29.9%(101/337)by RT-PCR.Statistical analysis showed that FCV prevalence was signifcantly associated with living environment(p=0.0004),age(p=0.031)and clinical symptoms(p=0.00),but not with sex(p=0.092)and breed(p=0.171).The 26 strains of FCV were isolated using F81 cells.Phylogenetic analysis showed that 10 isolates belonged to genotype I,and 16 isolates belonged to genotype II.These 26 isolates were highly genetically diverse,of which HB7 isolate had three same virulence-related amino acid loci with VSD strains.Potential loci distinguishing diferent genotypes were identifed from 26 isolates,suggesting the genetic relationship between diferent genotypes.In addition,selection pressure analysis based on capsid protein of 26 isolates revealed that the protein is under diversifying selection.This study reveals the genetic diversity of FCV and provides a reference for the screening of vaccine candidate strains and the development of vaccines with better cross-protection efects.