Meeting Abstract
Hybrid vigor has important consequences for fitness in natural populations and production in crop species, but its functional basis remains poorly understood. We used genome-wide SNP genotyping and global gene expression profiling to investigate the functional genomic basis for growth advantages in multiple hybrid crosses produced from inbred lines of the Pacific oyster Crassostrea gigas. Larvae from hybrid crosses showed the expected growth advantages, growing 18-75% faster than the corresponding parental lines. To investigate the genomic basis for this variation among hybrids we genotyped each parent using a sequencing based approach (2bRAD), identifying >4,000 polymorphisms (SNPs) among inbred lines. Genome-wide analysis of SNP genotypes revealed a strong relationship between genetic distance and hybrid vigor: offspring of genetically dissimilar lines grew more rapidly than offspring of genetically similar lines. Here we describe ongoing locus-by-locus analysis of these genetic data in the context of the genome assembly in search of the functional basis for variation in growth performance among hybrids. In parallel, we profiled gene expression in the same families using RNASeq to test for genes differentially expressed in hybrids than inbreds. Previous analysis of gene expression in hybrid oysters has implicated ribosomal protein (RP) genes in hybrid vigor. In this study we found similar patterns: “balanced” expression of RP genes in hybrids and “unbalanced” expression in inbreds. Our findings support the RP balance model of hybrid vigor, in which stoichiometric expression of RP genes in hybrids contributes to efficient ribosome assembly and growth while their uneven expression in inbreds contributes to reduced metabolic efficiency and growth.
