To understand the genetic basis that underlies the phenotypic divergence between human and non- human primates, we screened a total of 7176 protein-coding genes expressed in the human brain and compared them with the chimpanzee orthologs to identify genes that show evidence of rapid evolution in the human lineage. Our results showed that the nonsynonymous/synonymous substitution (Ka/Ks) ratio for genes expressed in the brain of human and chimpanzee is 0.3854, suggesting that the brain-expressed genes are under functional constraint. The X-linked human brain-expressed genes evolved more rapidly than autosomal ones. We further dissected the molecular evolutionary patterns of 34 candidate genes by sequencing representative primate species to identify lineage-specific adaptive evolution. Fifteen out of the 34 candidate genes showed evidence of positive Darwinian selection in human and/or chimpanzee lineages. These genes are predicted to play diverse functional roles in em- bryonic development, spermatogenesis and male fertility, signal transduction, sensory nociception, and neural function. This study together with others demonstrated the usefulness and power of phy- logenetic comparison of multiple closely related species in detecting lineage-specific adaptive evolu- tion, and the identification of the positively selected brain-expressed genes may add new knowledge to the understanding of molecular mechanism of human origin.
QI XueBinYANG SuZHENG HongKunWANG YinQiuLIAO ChengHongLIU YingCHEN XiaoHuaSHI HongYU xiaoJingAlice A. LINLuca L. CAVALLI-SFORZAWANG JunSU Bing
Through constructing the F-2 clonal population of an intercross,Teqing/Lemont,two quantitative trait loci(QTLs),qSB-9 and qSB-11,contributing to sheath blight resistance were preliminarily detected.Furthermore,from the F-2 clonal population of Teqing/Lemont,a double-susceptible and two double-resistant clonal lines was selected as pure parents and were separately intercrossed and backcrossed to recurrent parents,Teqing and Lemont.In BC-1F-1,marker-assisted selection was conducted and all backcrossed plants were inoculated by short toothpicks incubated with a strain,RH-9 of Rhizoctonia solani for identification of the resistance.In BC-2F-1,according to the similarity of integrative traits between backcrossed plants and their recurrent parents,we gathered BC-2F-2 seeds of some backcrosses.BC-2F-2 plants of coinciding requirement were selected through marker-assisted selection during the period of seedling stage,and separately mixed as homozygous lines.Thus,double-susceptible lines in the background of Teqing,double-susceptible and double-resistant lines in the background of Lemont were developed.The results of the inoculation test suggested that method of molecular marker-assisted selection for sheath blight resistance with investigation of disease ratings in backcross generations can quickly check up the reliability of location of resistant QTL and confirm the QTL interval on chromosome.
