Species tree disequilibrium positively misleads models of gene family evolution

Gene duplication is a key source of evolutionary innovation, and multigene families evolve in a birth-death process, continuously duplicating and pseudogenizing through time. To empirically test hypotheses about adaptive expansion and contraction of multigene families across species, models infer gene gain and loss in light of speciation events and these inferred gene family expansions may lead to interpretations of adaptations in particular lineages. While the relative abundance of a gene subfamily in the subgenome may reflect its functional importance, tests based on this expectation can be confounded by the complex relationship between the birth-death process of gene subfamily evolution and the species phylogeny. Using simulations, we confirmed tree heterogeneity as a confounding factor in inferring multi-gene adaptation, causing spurious associations between shifts in birth-death rate and lineages with higher branching rates. We then used the olfactory receptor (OR) repertoire, the largest gene family in the mammalian genome, of different bat species with divergent diets to test whether expansions in olfactory receptors are associated with shifts to frugivorous diets. After accounting for tree heterogeneity, we robustly inferred that certain OR subfamilies exhibited expansions associated with dietary shifts to frugivory. Taken together, these results suggest ecological correlates of individual OR gene subfamilies can be identified, setting the stage for detailed inquiry into within-subfamily functional differences.

Identification of 1093-bp intron A, SNPS and indels discovered in the porcine pregnancy-associated glycoprotein 2-like (pPAG2-L) gene subfamily in pigs

The objective of this study was to identify the intron A sequence (between exons 1 and 2) of pPAG2-L, novel single nucleotide polymorphisms (SNPs) and mutations (InDels) within intron A in the crossbreed (Landrace x Large White), Hirshmann hybrid and Duroc pigs. Genomic templates were isolated from leukocytes, amplified, and the gel-out were purified and then sequenced. Positive amplification control included CH242-60C13 BAC clone (Duroc) containing pPAG1-L and pPAG2-L. This is the first report that describes the 1093-bp intron A sequence from the pPAG2-L (Acc. No. KF471015; GenBank), which increased general knowledge of the porcine genome. Novel SNPs/InDels were identified within the intron A of the pPAG2-L in the crossbreeds (72), Duroc (45) and Hirshmann hybrids (17). This is a pioneer study describing identification of the intron A and SNPs/InDels in crossbreeds that provides a novel major pattern that represents a large portion of the genetic variation within the porcine genome. This information should be valuable when genotyping (coding and noncoding regions) multiparous sows from many breeds, in which reproductive phenotypes are known.

In silico Identification and Comparative Analysis of Hevea brasiliensis COBRA Gene Family

In this paper, the H. brasiliensis COBRA gene family, alleged to be involved in laticifer differentiation, was identified from the public rubber tree genome of Reyan 7-33-97 clone. A comparative analysis was carried out against A. thaliana genomic database. This analysis has resulted to the in silico validation of thirteen putative genes encoding glycophosphatidylinositol anchors (GPI) proteins harbored by nine Hevea genomic scaffolds. The sequence’s similarity of HbCOBL against AtCOBL genes were ranged from the threshold 50 to 81.58% covering 151 to 458 amino acid residues, respectively. Three partial and ten full-length protein sequences of HbCOBL genes were annotated. The partial protein sequences ranged from 89 to 184 amino acid residues as opposed to the full-length proteins ranging from 160 to 471 amino acid residues. Two types of COBRA domains (pfam04833 and cl04787) were found among HbCOBL genes. Phylogenetic analysis has clustered two subfamilies. Nine HbCOBL genes (HbCOBL-B, HbCOBL-J, HbCOBL-C, HbCOBL-H, HbCOBL-F, HbCOBL-I, HbCOBL-M, HBCOBL-A, and HbCOBL-N) were clustered as COBRA gene subfamily-I. By contrast, four genes (HbCOBL-O, HbCOBL-P, HbCOBL-E, and HbCOBL-L) were clustered as COBRA gene subfamily-II. The HbCOB subfamily-II was marked by the addition of 203 residues in C-terminal which is different with Arabidopsis. The gene HbCOBL-C was the putative ortholog to AtCOB carrying the unique COBRA domain cl04787 with 74 amino acid residues. Taken together, these results showed that Hevea and Arabidopsis COBRA genes might share similar functions while differ in gene structure.