甘蓝型油菜芥酸和二十碳烯酸含量的基因效应

以甘蓝型油菜的4种纯合芥酸基因型之间所有可能的6个杂交组合的P_1、P_2、F_1、P_2、B_1和B_2世代为材料,用生统遗传学方法研究了芥酸和二十碳烯酸的基因作用形式及效应。发现无论亲本是单基因差异还是二基因差异,F_1和F_2代的芥酸含量都接近中亲值,F_1略大于中亲值和F_(20)世代均值分析表明,芥酸含量的遗传符合加性显性模型,加性效应占绝对优势,显性效应不显著。用数量遗传学方法估计的芥酸基因数与已知的结果相近。     

Statistical techniques for detection of major genes in animal breeding data

Summary Statistical techniques for detection of major loci and for making inferences about major locus parameters such as genotypic frequencies, effects and gene action from field-collected data are presented. In field data, major genotypic effects are likely to be masked by a large number of environmental differences in addition to additive and nonadditive polygenic effects. A graphical technique and a procedure for discriminating among genetic hypotheses based on a mixed model accounting for all these factors are proposed. The methods are illustrated by using simulated data.Journal Paper No. J-12733 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 1901     

Molecular biology of wound-inducible proteinase inhibitors in plants

Abstract. The techniques of molecular biology are being employed to investigate at the gene level the systemically mediated, wound-induced accumulation of two defensive proteinase inhibitor proteins in plant leaves. These techniques have added a new dimension to biochemical and physiological studies already underway to understand the mechanism of induction by wounding. The acquisition of cDNAs from the RNAs coding for the two inhibitors facilitated studies of mRNA synthesis in leaves in response to wounding, and provided probes to obtain wound-inducible proteinase inhibitor genes from tomato ( Lycopersicon esculentum ) and potato (Solarium tuberosum) genomes. Successful transformations of tobacco plants with fused genes, containing the 5' and 3' regions of the inhibitor genes with the open reading frame of the chloramphenicol acelyltransferase ( cat ) gene, have provided a wound-inducible chloramphenicol acetyltransferase (CATase) activity with which to seek cis- and transacting elements that regulate wound-inducibility to help to understand the interaction of cytoplasmic and nuclear components of the intracellular communication systems that activate the proteinase inhibitor genes in response to wounding by insect pests.     

Synthesis and assembly of the cytochrome b-f complex in higher plants

The cytochrome b-f complex is composed of four polypeptide subunits, three of which, cytochrome f, cytochrome b-563 and subunit IV, are encoded in chloroplast DNA and synthesised within the chloroplast, and the fourth, the Rieske FeS protein, is encoded in nuclear DNA and synthesised in the cytoplasm. The assembly of the cytochrome b-f complex therefore requires the interaction of subunits encoded by different genomes. A key role for the nuclear-encoded Rieske FeS protein in the assembly of the complex is suggested by a study of cytochrome b-f complex mutants. The assembly of individual subunits of the complex may be regulated by the availability of prosthetic groups. The genes for the chloroplast-encoded subunits and cDNA clones for the Rieske FeS protein have been isolated and characterised. Cytochrome f and the Rieske FeS protein are synthesised initially with N-terminal presequences required for their correct assembly within the chloroplast. The deduced amino acid sequences of the four subunits have been used to suggest models for the arrangement of the polypeptides in the thylakoid membrane.     

The chalcone synthase multigene family of Petunia hybrida (V30): sequence homology,chromosomal localization and evolutionary aspects

Chalcone synthase (CHS) genes in Petunia hybrida comprise a multigene family containing at least 7 complete members in the strain Violet 30 (V30). Based on a high sequence homology in both coding and non-coding sequence, a number of CHS genes can be placed into two subfamilies. By restriction fragment length polymorphism (RFLP) analysis it was shown that both chromosomes II and V carry one of these subfamilies, in addition to the other CHS genes identified so far. Members of a subfamily were found to be closely linked genetically. Analysis of the Petunia species that contributed to the hybrid nature of P. hybrida (P. axillaris, P. parodii, P. inflata and P. violacea) shows that none of the CHS gene clusters is specific for either one of the parents and therefore did not arise as a consequence of the hybridization. The number of CHS genes within a subfamily varies considerably among these Petunia species. From this we infer that the CHS subfamilies arose from very recent gene duplications.     

The γ-crystallin gene families: Sequence and evolutionary patterns

Summary The -crystallin proteins consist of two topologically equivalent domains, each built up out of two similar motifs. They are encoded by a gene family, which already contained five members before the divergence of rodents and primates. A further gene duplication took place in each lineage. To analyze the pattern of evolution within this gene family, the coding sequences of six human genes, six rat genes, and four mouse genes were compared. Between species, a uniform rate of evolution of all regions of the protein is seen. The ratio of synonymous to nonsynonymous substitution in the human/rat or human/mouse comparison is much lower than the ratio when rat and mouse are compared indicating that the -crystallin proteins are better conserved in the rodent lineage. Within species, the regions encoding the two external motifs I and III of the protein show a greater extent of nonsynonymous substitution than the regions encoding the two internal protein motifs II and IV. The low extent of synonymous substitution between the second exons (encoding motifs I and II) of the rat -crystallin genes suggests the frequent occurrence of gene conversion. In contrast, a high extent of synonymous substitution is found in exon 3 (encoding motifs III and IV) of the rat genes. The same phenomenon is seen within the human gene family. The frequencies of occurrence of the various dinucleotides deviate less from those predicted from the frequencies of occurrence of each individual nucleotide in the second exons than in the third exons. The sequences of the third exons are significantly depleted in CpG, ApA, and GpT and enriched in CpT and GpA.     

Cloning and sequencing of the genes encoding the large and the small subunits of the H2 uptake hydrogenase (hup) of Rhodobacter capsulatus

Summary The structural genes (hup) of the H₂ uptake hydrogenase of Rhodobacter capsulatus were isolated from a cosmid gene library of R. capsulatus DNA by hybridization with the structural genes of the H₂ uptake hydrogenase of Bradyrhizobium japonicum. The R. capsulatus genes were localized on a 3.5 kb HindIII fragment. The fragment, cloned onto plasmid pAC76, restored hydrogenase activity and autotrophic growth of the R. capsulatus mutant JP91, deficient in hydrogenase activity (Hup^-). The nucleotide sequence, determined by the dideoxy chain termination method, revealed the presence of two open reading frames. The gene encoding the large subunit of hydrogenase (hupL) was identified from the size of its protein product (68108 dalton) and by alignment with the NH₂ amino acid protein sequence determined by Edman degradation. Upstream and separated from the large subunit by only three nucleotides was a gene encoding a 34 256 dalton polypeptide. Its amino acid sequence showed 80% identity with the small subunit of the hydrogenase of B. japonicum. The gene was identified as the structural gene of the small subunit of R. capsulatus hydrogenase (hupS). The R. capsulatus hydrogenase also showed homology, but to a lesser extent, with the hydrogenase of Desulfovibrio baculatus and D. gigas. In the R. capsulatus hydrogenase the Cys residues, (13 in the small subunit and 12 in the large subunit) were not arranged in the typical configuration found in [4Fe–4S] ferredoxins.