Development of Wide-Compatible Indica Lines by Pyramiding Multiple Neutral Alleles of Indica-Japonica Hybrid Sterility Loci.

Since the development of indica hybrid rice in the 1970s, great success has been achieved in hybrid rice production in China and around the world. The utilization of inter-subspecific indica-japonica hybrid rice has always been considered due to its stronger heterosis characteristics. However, indica-japonica hybrids face a serious problem of sterility, which hinders the exploitation of their heterosis. In the past decades, the genetic basis of indica-japonica hybrid sterility has been well studied. It was found that in sterile indica-japonica hybrids, female sterility was mainly controlled by the S5 locus and male sterility by the Sa, Sb, Sc, Sd, and Se loci. In this study, we developed wide-compatible indica lines (WCILs) by pyramiding multiple neutral (n) alleles of the hybrid sterility loci. First, we identified Sn alleles of the loci in single-segment substitution lines (SSSLs) in the genetic background of indica Huajingxian 74 (HJX74). Then, the Sn alleles of S5, Sb, Sc, Sd, and Se loci in SSSLs were pyramided in the HJX74 genetic background. The WCILs carrying Sn alleles at the S5, Sb, Sc, Sd, and Se loci showed wide compatibility with indica and japonica rice varieties. Therefore, the WCILs will be used to develop inter-subspecific indica-japonica hybrid rice with normal fertility.

Neutral alleles at hybrid sterility loci of Oryza glaberrima from AA genome relatives in Genus Oryza.

Hybrid sterility between Oryza sativa and O. glaberrima is a main reproduction barrier when transferring the favorable alleles from O. glaberrima to O. sativa and it happens due to allelic interaction at sterility loci. Neutral alleles at each locus have the potential to overcome the sterility between the two cultivated rice species. In this study, an O. sativa cultivar Dianjingyou 1 (DJY1) and its near-isogenic lines (NILs) harboring the single sterility allele S1-glab, S19-glab, S20-glab, S37-glab, S38-glab and S39-glab as the tested lines were crossed with O. glaberrima, O. rufipogon, O. nivara, O. glumaepatula, O. barthii, O. meridionalis and O. sativa so as to detect the neutral alleles of these loci. Pollen fertility was investigated in the paired F1s based on two seasons' result and genotypic segregation was also analyzed in some F2 populations to confirm the results of pollen fertility investigation. The neutral alleles of S38-n and S39-n were identified based upon the pollen fertility and genotypic segregation analysis for the first time. The neutral alleles of sterility loci detected from present report have the potential to know of the nature of interspecific hybrid sterility, and to overcome the interspecific hybrid sterility between O. sativa and O. glaberrima.

Both qualitative and quantitative genetic variation of MHC class II molecules may influence susceptibility to autoimmune diseases: the case of endemic pemphigus foliaceus.

The MHC class II transactivator (CIITA) is a key regulator in expression of the HLA class II genes. It is well known that HLA-DRB1 genotypes have a strong influence on the risk of multifactorial autoimmune diseases, but the effect of CIITA genotypes remains controversial. We tested in a case-control study whether CIITA polymorphisms influence the risk of developing endemic pemphigus foliaceus (EPF) and whether CIITA and HLA-DRB1 interact as regards susceptibility to the disease. The rs4774 SNP is not associated to EPF, while rs3087456 in the CIITA gene promoter is associated with susceptibility [odds ratio (OR) = 2.6, p < 0.001 and OR = 2.0 p = 0.003 for genotypes G/G and G/A, respectively]. We suggest that the associations result from the effect of genetically controlled levels of CIITA on expression of the susceptible and protective HLA class II molecules. Remarkably, the interaction between CIITA and HLA-DRB1 genotypes is strong and additive. The OR for individuals having two susceptible HLA-DRB1 alleles is 14.1 in presence of the susceptible CIITA G/G or G/A genotypes and much lower (2.2) in presence of the protective CIITA A/A genotype. We conclude that quantitative as well as qualitative variation of HLA class II molecules have an effect on the risk of an individual developing EPF.

SUBSTITUTION PROCESSES IN MOLECULAR EVOLUTION. II. EXCHANGEABLE MODELS FROM POPULATION GENETICS.

Substitution processes are of two sorts: origination processes record the times at which nucleotide mutations that ultimately fix in the population first appear, and fixation processes record the times at which they actually fix. Substitution processes may be generated by combining models of population genetics-here the symmetrical-neutral, overdominance, underdominance, TIM, and SAS-CFF models-with the infinite-sites, no-recombination model of the gene. This paper is mainly concerned with a computer simulation study of these substitution processes. The rate of substitution is shown to be remarkably insensitive to the strength of selection for models with strong balancing selection caused by the genealogical drift of mutations through alleles held in the population by selection. The origination process is shown to be more regular than Poisson for the overdominance, TIM, and SAS-CFF models but more clustered for the underdominance model. A class of point processes called Sawyer processes is introduced to help explain these observations as well as the observation that the times between successive originations are nearly uncorrelated. Fixation processes are shown to be more complex than origination processes, with regularly spaced bursts of multiple fixations. An approximation to the fixation process is described. One important conclusion is that protein evolution is not easily reconciled with any of these models without adding perturbations that recur on a time scale that is commensurate with that of molecular evolution.