水稻体细胞无性系R_1、R_2代中的雄性育性变异观察

通过水稻幼穗培养,１９９１－１９９２两年间,在５个品种（珍汕９７Ｂ、红源Ａ、包源Ａ、Ｗ６１５４ｓ,和南广占）中共获得了５０株雄性不育变异株,其中Ｒ_１代有４８株,Ｒ_２代有２株。在Ｒ１代,共获得５２６８株再生植株,雄性不育变异的平均频率为０．９１％（０．８３－１．０８％）;在Ｒ_２代（珍汕９７Ｂ）发生雄性不育变异的频率为２％。本文报道了多种花粉败育类型之间可以相互转变现象,此外不育和可育之间亦可以相互转变。对离体培养产生的雄性不育变异株用一批现有ＣＭＳ（Ｃｙｔｏｐｌａｓｍｉｃｍａｌｅｓｔｅｒｉｌｅ）不育系的典型保持系、恢复系进行测交,结果表明,Ｗ６１５４ｓ产生的雄性育性变异株仍保持核不育的特性;红源Ａ产生的雄性育性变异株有的可能是嵌合体,有的其败育花粉类型虽发生了变化,但其恢保关系并没有改变,有的则可能已转成类似ＷＡ型的不育材料;南广占产生的典败变异株,其恢保关系类似ＷＡ型,可能属核不育转成ＣＭＳ的首例发现。     

纯系间数量性状主基因差异的遗传分析

将Ｅｌｓｔｏｎ模型应用于存在主基因差异的系间杂交的分离世代分析,提出利用似然函数分析数量性状的尺度效应、主基因分离比例以及主基因效应和微基因效应的方法,并应用于水稻遗传实验,结果表明,半矮秆籼稻品种南京１１号带有的隐性矮秆主基因,效应大约为４０－５６ｃｍ,微基因效应以加性为主,且主、微型基因存在显著互作,但互作和微基因效应均远小于基因效应。     

Establishment processes and regeneration patterns of montane virgin coniferous forest in northeastern China

Abstract. The co-occurrence of Larix olgensis var. changpaiensis, Picea jezoensis and Abies nephrolepis in the coniferous forest of Mount Changbai, northeastern China, is discussed, and the regeneration pattern of these taxa compared on the basis of the analysis of the age structure and the age-height relationship of the three conifers. The presence of tall individuals (ca. 30 m in height) of Larix olgensis var. changpaiensis, which does not show any regeneration, was related to the large eruption of Mount Changbai up to ca. 400 yr ago. Picea jezoensis compensates its small recruitment by a large stem size and long life span together with a continuous height growth. Abies nephrolepis recruits well, but its small stem size and short life span do not result in its dominance in the forest.     

AT4 receptor structure-binding relationship: N-terminal-modified angiotensin IV analogues

The effect of structural changes in the N-terminal amino acid of AIV, with respect to AT₄ receptor binding, was examined by competition with [¹²⁵I]AIV in bovine adrenal membranes. Analogues with modifications of the first residue α-amino group possessed lower affinities than the primary amine-containing parent compound. Peptides with a residue 1 α-carbon in the d conformation exhibited poor affinity for the AT₄ receptor. Modifications of the residue 1 R-group demonstrate that a straight chain aliphatic moiety containing four carbons is optimal for receptor-ligand binding, as evidenced by the extremely high affinity of [Nle¹]AIV (K_i = 3.59±0.51 pM). Replacement of the 1–2 peptide bond of AIV with the methylene bond isostere Ψ (CH₂-NH), increased the K_i approximately fivefold, indicating that the peptide bond may be replaced wihle maintaining relatively high-affinity receptor binding.     

AT4 receptor structure-binding relationship: N-terminal-modified angiotensin IV analogues

The effect of structural changes in the N-terminal amino acid of AIV, with respect to AT₄ receptor binding, was examined by competition with [¹²⁵I]AIV in bovine adrenal membranes. Analogues with modifications of the first residue -amino group possessed lower affinities than the primary amine-containing parent compound. Peptides with a residue 1 -carbon in the conformation exhibited poor affinity for the AT₄ receptor. Modifications of the residue 1 R-group demonstrate that a straight chain aliphatic moiety containing four carbons is optimal for receptor-ligand binding, as evidenced by the extremely high affinity of [Nle¹]AIV (K_i = 3.59±0.51 pM). Replacement of the 1–2 peptide bond of AIV with the methylene bond isostere Ψ (CH₂-NH), increased the K_i approximately fivefold, indicating that the peptide bond may be replaced wihle maintaining relatively high-affinity receptor binding.     

Regional Profile of Developmental Changes in the Sensitivity of the N-Methyl-D-Aspartate Receptor to Polyamines

Abstract: The NMDA receptor exhibits increased sensitivity to stimulation during early development compared with the adult. In this study, we examined modulation of the NMDA receptor by polyamines during development to see if it correlates with differences in the functional responsiveness of the NMDA receptor. [³H]MK-801 binding was measured in discrete brain regions in the presence and absence of polyamines in 3-, 7-, 15-, 25-, and 60-day-old Sprague-Dawley rats. [³H]MK-801 binding increased between postnatal days 3 and 15, with adult levels of binding being reached between days 15 and 25. Spermidine (75 μM) caused maximal stimulation of [³H]MK-801 binding during early development, ranging from 250% in the thalamus to 450% in the caudate putamen at postnatal day 3. This effect gradually declined to levels seen in the adult by postnatal days 15–25. During all developmental stages, the stimulation seen was greater in the caudate putamen compared with the hippocampus. Diethylenetriamine (1 μM) exhibited similar developmental and regional heterogeneity in its effects on [³H]MK-801 binding, producing substantial stimulation of binding in the neonate, but not in the adult. The EC₅₀ and E_max values for the stimulatory effect of spermidine were significantly higher at day 7 compared with the adult. Unlike spermidine and diethylenetriamine, there was no regional variation in the effects of the putative “polyamine site” inverse agonist 1,10-diaminodecane at any age and only a slightly attenuated inhibition at postnatal day 3 compared with the adult. This lack of complementarity in the regional and developmental profiles of spermidine and diethylenetriamine, on the one hand, and 1,10-diaminodecane, on the other, suggests that their effects on [³H]MK-801 binding are mediated at different sites. The altered sensitivity of the NMDA receptor to polyamines during development could reflect the expression of molecular variants with different sensitivities to modulation by polyamines.     

Quantitative genetics of growth and development in Populus. I. A three-generation comparison of tree architecture during the first 2 years of growth

One approach to gain an insight into the genetics of tree architecture is to make use of morphologically divergent parents and study their segregating progeny in the F₂ and backcross (B₁) generations. This approach was chosen in the present study in which material of a three-generation pedigree growing side by side in a replicated plantation, was analyzed. The pedigree included Populus trichocarpa (T) and P. deltoides (D) parents, their F₁ and F₂ hybrids and their B₁ hybrids to the D parent. The trees were grown in the environment of the T parent and measured for the first 2 years of growth. Nine quantitative traits were studied at the stem, branch and leaf levels of tree architecture, in which the original parents differed. Strong F₁ hybrid vigor relative to the better parent (T) was expressed in growth and its components. Most quantitative traits in the F₂ and B₁ hybrids were intermediate between the T and D parents but displayed a wide range of variation due to segregation. The results from the analysis of variance indicated that all morphometric traits were significantly different among F₂ and B₁ clones, but the B₁ hybrids were more sensitive to replicates than the F₂. Broad-sense heritabilities (H ²) based on clonal means ranged from moderately high to high (0.50–0.90) for the traits studied, with H ² values varying over age. The H ² estimates reflected greater environmental noise in the B₁ than in the F₂, presumably due to the greater proportion of maladaptive D alleles in those hybrids. In both families, sylleptic branch number and length, and leaf size on the terminal, showed strong genetic correlations with stem growth. The large divergence between the two original parents in the traits studied, combined with the high chromosome number in Populus (2n=38), makes this pedigree well suited for the estimation of the number of quantitative trait loci (QTLs) underlying quantitative variation by Wright's biometric method (1968). Variation in several traits was found to be under the control of surprisingly few major QTLs: 3–4 in 2nd-year height and diameter growth, a single QTL in stem diameter/height ratio.     

QTL analysis: a simple ‘marker-regression’ approach

A method to locate quantitative trait loci (QTL) on a chromosome and to estimate their additive and dominance effects is described. It applies to generations derived from an F₁ by selfing or backcrossing and to doubled haploid lines, given that marker genotype information (RFLP, RAPD, etc.) and quantitative trait data are available. The method involves regressing the additive difference between marker genotype means at a locus against a function of the recombination frequency between that locus and a putative QTL. A QTL is located, as by other regression methods, at that point where the residual mean square is minimised. The estimates of location and gene effects are consistent and as reliable as conventional flanking-marker methods. Further applications include the ability to test for the presence of two, or more, linked QTL and to compare different crosses for the presence of common QTL. Furthermore, the technique is straightforward and may be programmed using standard pc-based statistical software.     

Genetic analysis of morphological variation in Brassica oleracea using molecular markers

A cross between the open-pollinated Brassica oleracea cabbage cultivar Wisconsin Golden Acre and the hybrid broccoli cultivar Packman was used with molecular markers to investigate the genetic control of morphological variation. Twenty-two traits derived from leaf, stem, and flowering measurements were analyzed in 90 F₂ individuals that were also classified for genotype by restriction fragment length polymorphism (RFLP) markers. Seventy-two RFLP loci, which covered the mapped genome at an average of 10 map-unit intervals on all nine linkage groups, were tested individually for associations to phenotypic measurements by single factor ANOVA, and markers with significant associations (P<0.05) were used to develop multilocus models. These data were utilized to describe the location, parental contribution of alleles, magnitude of effect, and the gene action of trait loci. Single marker loci that were significantly associated (P<0.05) with trait measurements accounted for 6.7–42.7% of the phenotypic variation. Multilocus models described as much as 60.1% of the phenotypic variation for a given trait. In some cases, different related traits had common marker-locus associations with similar gene action and genotypic class ranking. The numbers, action, and linkages, of genes controlling traits estimated with marker loci in this population corresponded to estimates based on classical genetic methods from other studies using similar, or similarly-wide, crosses. There was no evidence that genome duplication accounted for a significant portion of multiple genes controlling trait loci over the entire genome, but possible duplications of trait loci were identified for two regions with linked, duplicated marker loci.     

Location of a gene regulating drought-induced abscisic acid production on the long arm of chromosome 5A of wheat

The accumulation of abscisic acid (ABA) by detached and partially dehydrated wheat leaves is known to be inherited in a quantitative manner. The location of genes having a major effect on drought-induced ABA accumulation in wheat was determined using a set of single chromosome substitution lines and populations derived from a cross between a high-ABA- and a low-ABA-producing genotype. Examination of a series of chromosome substitution lines of the high-ABA genotype Ciano 67 into the low-ABA recipient Chinese Spring showed that chromosome 5A carries gene(s) that have a major influence on ABA accumulation in a drought test with detached and partially dehydrated leaves (DLT). A similar DLT was used to examine ABA accumulation in a population of F₂ plants and doubled haploid (DH) lines derived from the cross between Chinese Spring (low-ABA) and SQ1 (high-ABA) in which the F₂ population (139 plants) and DH lines (96 lines) were also mapped partially with molecular markers. Analysis of variance of ABA accumulation between and within marker allele classes in the F₂ confirmed the location of a gene(s) regulating ABA accumulation on the long arm of chromosome 5A. MAPMAKERQTL showed the most likely position for the ABA quantitative trait locus (QTL) to be between the loci Xpsr575 and Xpsr426, about 8 cM from Xpsr426. A similar trend for high ABA accumulation was found in DH lines having the SQ1 allele at marker loci in the same region of chromosome 5AL, but the QTL effect was not significant. The function of the QTL is discussed.