Analysis of the genetic characteristics and variations in disease-resistant grass carp based on whole-genome resequencing and transcriptome sequencing

Disease-resistant grass carp (DR-GGC) was obtained by backcrossing gynogenetic grass carp (GGC, 2n = 48, female) with common grass carp (Ctenopharyngodon idellus [GC], 2n = 48, male). The genetic constitution and the potential mutation associated with growth dominance in DR-GGC were analyzed by genomic in situ hybridization (GISH), whole-genome resequencing (WGRS) and RNA-sequencing (RNA-seq). The GISH results showed partial translocations and deletions in the chromosomes of DR-GGC compared with GC. The WGRS results demonstrated that there were numerous genetic variations between DR-GGC and its parents, among which DR-GGC had the highest genomic heterozygosity and GGC had the highest genomic purity. The RNA-seq results revealed that the differentially expressed genes (DEGs) were significantly enriched in cellular processes and immune pathways in DR-GGC and GGC compared with GC. Meanwhile, the combined analysis of WGRS and RNA-seq identified DEGs with overlapping mutation loci in DR-GGC and GGC compared with GC. These DEGs were significantly enriched in the pathways of growth, metabolism, and immunity, including cellular metabolism, biosynthesis, glycolysis/gluconeogenesis, and extra cellular matrix (ECM) receptor interactions. These results provide a genetic basis for exploring the better growth characteristics and disease resistance of DR-GGC than GC, valuable information on the genetic breeding for grass carp, and a further understanding of the genetic characteristics of gynogenetic individuals.