Self-incompatibility (SI) inBrassica is controlled sporophytically by the multiallelic S -locus. The SI phenotype of pollen in an S -heterozygote is determined by the relationship between the two S -haplotypes it carries, and dominant/recessive relationships often are observed between the two S -haplotypes. The S -locus protein 11 ( SP11 , also known as the S -locus cysteine-rich protein) gene has been cloned from many pollen-dominant S -haplotypes (class I) and shown to encode the pollen S -determinant. However, SP11 from pollen-recessive S -haplotypes (class II) has never been identified by homology-based cloning strategies, and how the dominant/recessive interactions between the two classes occur was not known. We report here the identification and molecular characterization of SP11 s from six class II S -haplotypes of B. rapa and B. oleracea . Phylogenetic analysis revealed that the class II SP11s form a distinct group separated from class I SP11s. The promoter sequences and expression patterns of SP11 s also were different between the two classes. The mRNA of class II SP11 , which was detected predominantly in the anther tapetum in homozygotes, was not detected in the heterozygotes of class I and class II S -haplotypes, suggesting that the dominant/recessive relationships of pollen are regulated at the mRNA level of SP11 s. INTRODUCTIONMany species of hermaphrodite plants have evolved mechanisms to prevent self-fertilization. Self-incompatibility (SI) is one physiological means of avoiding self-fertilization through recognition of self-pollen in or on the female pistil. Classic genetic analyses have revealed the presence of two major types of homomorphic SI systems, gametophytic and sporophytic (de Nettancourt, 1977). Although the recognition of self-pollen is controlled genetically by a single highly polymorphic locus called the S -locus in both of these systems, the SI phenotype of pollen (gametophyte) is determined by its own S -haplotype in the gametophytic system, whereas in the sporophytic system, the SI phenotype is controlled by the S -haplotypes of the diploid parent (sporophyte).The majority of the members of the cruciferous plant genus Brassica possess a strong sporophytic SI system. Thus, the SI phenotype of pollen as well as stigma is determined by relationships between the two S -haplotypes carried by its parent (Bateman, 1955). In other words, a codominant or a dominant/recessive relationship between the two S -haplotypes influences the ultimate SI phenotype of both pollen and stigma (Thompson and Taylor, 1966). The following observations have been made about dominance relationships among S -haplotypes: (1) codominance is common; (2) dominance/recessiveness is frequent in pollen; (3) dominance relationships among stigmas are different from those among pollen; and (4) dominance relationships are nonlinear (Thompson and Taylor, 1966;Ockendon, 1975;Visser et al., 1982; Hatakeyama et al., 1998a).Recent molecular studies have revealed that the S -locus of Brassica encodes three highly polymorphic ...
In this study, experimental Ti-Ag alloys (5, 10, and 20mass% Ag) and Ti-Cu alloys (2, 5, and
Highly divergent sequences of the pollen self-incompatibility (S) gene in class-I S haplotypes of Brassica campestris (syn. rapa) L. Edited by Ulf-Ingo Flu « gge Abstract Self-incompatibility (SI) enables flowering plants to discriminate between self-and non-self-pollen. In Brassica, SI is controlled by the highly polymorphic S locus. The recently identified male determinant, termed SP11 or SCR, is thought to be the ligand of S receptor kinase, the female determinant. To examine functional and evolutionary properties of SP11, we cloned 14 alleles from class-I S haplotypes of Brassica campestris and carried out sequence analyses. The sequences of mature SP11 proteins are highly divergent, except for the presence of conserved cysteines. The phylogenetic trees suggest possible co-evolution of the genes encoding the male and female determinants.z 2000 Federation of European Biochemical Societies.
Anodic polarization tests were performed in 0.9% NaCl and 1% lactic acid solutions to characterize the relationship between the corrosion behavior and the microstructures of cast Ti-Ag(5 -40% Ag)alloys. The anodic polarization curves for the TiAg alloys up to 17.5% Ag were similar to those for pure titanium in both solutions. On the other hand, an abrupt increase in the current density was observed for the alloys with more than 20% Ag in the NaCl solution and with more than 27.5% Ag in the lactic acid solution. The microstructures of the corroded alloy surfaces indicated the deterioration of precipitated intermetallic compounds along the grain boundaries. The Ti-Ag alloys up to 17.5% Ag had excellent corrosion resistance similar to that of pure titanium. The alloys with 20-25% Ag may be also used as dental alloys, since they passivated again immediately after preferential dissolution in the NaCl solution.
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