Genetic Analysis of Growth in Tomato: Segregating Generations

Genetical control of certain aspects of plant development hasbeen studied in the segregating generations derived from a diallelcross involving three varieties of L. esculentum and one ofL. pimpinellifolium. In the first experiment, dry-weight relativegrowth-rate was found to be inherited additively with a largedominance component which, however, was probably overestimatedin the F₁ by the inclusion of only one type of reciprocal cross.Gene association in the parents was suggested by the distributionof the points in the diallel regression graph. In a second experiment,the increase in leaf number with time was followed in parental,F₁, F₂, F₃, and backcross generations. Genetical analysis forvarious parameters of rates of production of leaves showed thecontrol to be additive with various degrees of dominance, andsimilar results were found for analysis of results on time-to-floweringand fruit yields. There was, throughout the experiments, agreementbetween the results for each generation. It is believed thatcombined genetical and physiological studies of growth in cropplants will be of value in the selection of parents for breedingimproved varieties.     

Genetic variance in the F2 generation of divergently selected parents

 Either by selective breeding for population divergence or by using natural population differences, F₂ and advanced generation hybrids can be developed with high variances. We relate the size of the genetic variance to the population divergence based on a forward and backward mutation model at a locus with two alleles with additive gene action. The effects of population size and initial gene frequency are also explored. Larger parental population sizes increase the F₂ genetic variance if the initial probability distribution is uniform or U-shaped. However, population size has the opposite effect if the initial distribution of gene frequencies is skewed such as it would be with newly arriving alleles. These alleles contribute to the genetic variance sooner when the selection pressure is higher or when the effective population size is smaller. Received: 5 April 1998 / Accepted: 22 April 1998     

POU1F1基因的遗传变异对南阳牛生长发育性状的影响

利用PCR-RFLP技术首次研究了南阳牛群体100个个体POU1F1基因多态性及其与体重、体尺等生长性状指标之间的相关性。结果表明,南阳牛群体POU1F1基因座的451bp的PCR产物被限制性酶Hinf Ⅰ消化后表现多态性,它们的等位基因A／B频率为：0．465／0．535,且处于Hardy-Weinberg平衡状态。同时,南阳牛群体POU1F1-Hinf Ⅰ基因座不同基因型与体重、体尺等生长性状指标相关分析的结果表明：南阳牛群体内BB与AB基因型个体在初生重、断奶前平均日增重、六月龄体重、体斜长和胸围以及十二月龄的体重、体高、体斜长和胸围指标上有显著差异,且BB〉AB（P〈0．05）;群体内BB型个体在十二月龄体重指标上显著高于群体的AA型个体,即BB〉AA（P〈0.05）,在其他各年龄段的各项体重和体尺指标上同样呈现出B等位基因高于A等位基因的一种趋势。初步认为BB基因型为优势基因型,相应地B为优势等位基因,对选择有正向效应,提示POU1F1基因的占等位基因可能与高生长发育性状有关。     

番茄果实乙烯释放量的遗传模型分析

本试验选择2个番茄果实乙烯释放量显著不同的番茄品系,通过P_1、P_2、F_1、F_2、B_1和B_2六世代的分析方法,研究了番茄果实乙烯释放量的遗传规律.结果表明:番茄果实乙烯释放量遗传符合1对负向完全显性主基因+加性-显性多基因模型(D-4),主基因效应在B_1、B_2和F_(23)个世代的遗传率分别为36.33%、44.09%和35.14%,多基因效应在B_1、B_2和F_(23)个世代的遗传率分别为54.73%、40.50%和54.88%.     

Effect of Genetic Variations of the POU1F1 Gene on Growth Traits of Nanyang Cattle

PCR-RFLP was applied to analyze the effect of the genetic variations of the POU1F1 gene on growth traits of 100 Nanyang cattle. The results showed that the 451 bp PCR product digested with Hinf I demonstrated polymorphism in the population, which was at Hardy-Weinberg equilibrium. Moreover, the frequencies of alleles A/B in the Nanyang population were 0.465/0.535. The association of the variations of the POU1F1 gene with the growth traits in the population was analyzed. The following parameters were greater in individuals with a genotype BB than in those with an genotype AB: birth weight, average weight increase before ablactation, body height at 12 months, body weight, body length, and chest girth at 6 months and 12 months (P<0.05). The body weight at 12 months was higher in the BB individuals than in the AA individuals (P <0.05). The body weight and body sizes also showed a trend of allele B> allele A in the other age groups. Therefore, the genotype BB maybe a dominant genotype and the allele B may be a dominant allele. These results imply that the allele B of the POU1F1 gene is likely to positively affect the growth traits.     

Application of Alcohol Dehydrogenase Loci in Testing F1 Hybridity of Tomato

Expression of alcohol dehydrogenase loci was used to estimate hybridity of Lycopersicon esculentum Mill. in 1012 seeds. The banding patterns were obtained by means of vertical block electrophoresis in polyacrylamide gels. It was established that qualitative variation of locus Adh-2 can be applied to prove hybridity of F₁ tomato seeds. This genetic marker is indicative for hybrids with fertile maternal line or with position male sterility line and not only for maternal line with pollen male sterility. This revised version was published online in July 2006 with corrections to the Cover Date.     

SARS S1基因对番茄的遗传转化与转基因番茄植株的获得

利用DNA直接导入法将含有SARS S1基因的植物表达载体pCS1导入农杆菌LBA4404中,并通过农杆菌介导的叶盘转化法得到12株再生小苗。PCR、Southern杂交检测结果证实,有6株为真正的转基因植株。     

Torque generation and utilization in motor enzyme F0F1-ATP synthase: half-torque F1 with short-sized pushrod helix and reduced ATP Synthesis by half-torque F0F1

ATP synthase (F(0)F(1)) is made of two motors, a proton-driven motor (F(0)) and an ATP-driven motor (F(1)), connected by a common rotary shaft, and catalyzes proton flow-driven ATP synthesis and ATP-driven proton pumping. In F(1), the central γ subunit rotates inside the α(3)β(3) ring. Here we report structural features of F(1) responsible for torque generation and the catalytic ability of the low-torque F(0)F(1). (i) Deletion of one or two turns in the α-helix in the C-terminal domain of catalytic β subunit at the rotor/stator contact region generates mutant F(1)s, termed F(1)(1/2)s, that rotate with about half of the normal torque. This helix would support the helix-loop-helix structure acting as a solid "pushrod" to push the rotor γ subunit, but the short helix in F(1)(1/2)s would fail to accomplish this task. (ii) Three different half-torque F(0)F(1)(1/2)s were purified and reconstituted into proteoliposomes. They carry out ATP-driven proton pumping and build up the same small transmembrane ΔpH, indicating that the final ΔpH is directly related to the amount of torque. (iii) The half-torque F(0)F(1)(1/2)s can catalyze ATP synthesis, although slowly. The rate of synthesis varies widely among the three F(0)F(1)(1/2)s, which suggests that the rate reflects subtle conformational variations of individual mutants.     

Sink Metabolism in Tomato Fruit : IV. Genetic and Biochemical Analysis of Sucrose Accumulation

Fruit of domesticated tomato (Lycopersicon esculentum) accumulate primarily glucose and fructose, whereas some wild tomato species, including Lycopersicon chmielewskii, accumulate sucrose. Genetic analysis of progeny resulting from a cross between L. chmielewskii and L. esculentum indicated that the sucrose-accumulating trait could be stably transferred and that the trait was controlled by the action of one or two recessive genes. Biochemical analysis of progeny resulting from this cross indicated that the sucrose-accumulating trait was associated with greatly reduced levels of acid invertase, but normal levels of sucrose synthase. Invertase from hexose-accumulating fruit was purified and could be resolved into three isoforms by chromatofocusing, each with isoelectric points between 5.1 and 5.5. The invertase isoforms showed identical polypeptide profiles on sodium dodecyl sulfate polyacrylamide gel electrophoresis, consisting of a primary 52 kilodalton polypeptide and two lower molecular mass polypeptides that appear to be degradation products of the 52 kilodalton polypeptide. The three invertase isoforms were indistinguishable based on pH, temperature, and substrate concentration dependence. Immunological detection of invertase indicated that the low level of invertase in sucrose-accumulating fruit was due to low levels of invertase protein rather than the presence of an invertase inhibitor. Based on comparison of genetic and biochemical data we speculate that a gene either encoding tomato fruit acid invertase or one required for its expression, plays an important role in determining sucrose accumulation.     

Analysis of Variation in the Rates of Germination and Early Seedling Growth in Tomato

Studies have been made on the time to germination and earlyseedling growth of the tomato Lycopersicon esculentum var. Potentateand Lycopersicon pimpinellifolium var. Red Currant, as wellas on derivative generations from their hybridization. Althoughtime to germination showed a genetic component, the relationshipsbetween different genotypes was much influenced by environmentalfactors. A marked maternal effect on time to germination dueto the varying seed sizes was noted while variation betweendifferent genotypes of similar seeds size was ascribed to anendospermic effect. The F¹ hybrid embryo with L. Pimpinellifoliumas maternal parent contained more cells than that of the parentbut the hybrid cmbryo with L. esculentum as maternal parentcontained a similar number of cells to that of the parent itself.It is suggested that the results for embryo size both supportAshby‘s assertion that embryo size may be important indetermining heterosis, and also Hatcher’s findings in1940, that heterosis for hypocotyl extension is found in hybridsfrom parcnts of different sized seeds provided the small seededvariety is the maternal parent.     

An Analysis of the Effects of Gibberellic Acid on Tomato Leaf Growth

The effects of four consecutive daily sprays of gibberellicacid (GA₃) on the growth of leaves of young tomato plants cv.Potentate were studied. Total leaf weight and area were increasedby GA₃. The percentage changes were larger in the younger leavesthan in the older but the absolute increases of the middlleleaves accounted for most of the total response. Chlorophyllcontent, both total and per unit weight, was reduced by GA inthe older leaves and increased in the younger; on an area basisit was reduced in all but the youngest leaves. Palisade cell length and palisade cell number per unit sectionlength were reduced by GA₃ in the oldest leaves and increasedin the youngest. There were larger intercellular spaces in bothmesophyll layers and a larger transectional area of the mid-ribsof the oldest and two youngest leaves in GA₃ plants. The ‘surfaceareas’ of epidermal cells were also increased by GA₃ treatment.Leaf fresh weight per unit area was only a true index of laminathickness in the two oldest leaves.     

Carbon Translocation in the Tomato: Carbon Import and Fruit Growth

The rates of carbon import by fruits were measured over 48 has the sum of the change in the total organic carbon contentof the fruit and the respiratory loss of carbon. Over a rangeof fruit sizes from 20–90 per cent of the maximum volumethe smaller fruits imported carbon at an absolute rate (mgCfruit^–1 h^–1) nearly twice that of the larger fruits.The imported leaf assimilates, identified as the ¹⁴C-compoundsalong the pathway between a ¹⁴CO₂-fed leaf and a young fruit,comprised 90 per cent sucrose and 10 per cent glutamic acid,aspartic acid and malic acid. Within the fruit the imported¹⁴C-sucrose was hydrolysed into hexoses. The changes in thelevels of starch and insoluble residue in the fruit were positivelycorrelated with the carbon import rates. In the largest fruitswith the lowest import rates, there was breakdown of insolubleresidue and less accumulation of starch, but a significant increasein the level of sucrose. The sink strength of a tomato fruitis dependent more on sink activity than on sink size.     

A Genetic Analysis of Targeted Growth in Mice

Effects of normal growth regulation on components of phenotypic variance and covariance of body weight were examined in a cross-fostering study of growth between 2 and 10 wk of age in ICR randombred mice. Different early growth rates caused genetic, postnatal maternal and residual environmental variances to increase, but these variances were subsequently reduced by negative autocorrelation between early and later growth. Postnatal maternal variance continued to increase for about 1 wk after weaning but then decreased substantially. Genetic variance caused by preweaning growth followed a pattern of increase and decrease very similar to that of postnatal maternal variance, but this pattern was masked by new genetic variance. Normal growth regulation affects the magnitudes of genetic variances and serial autocorrelations. The timing of these changes suggests that regulation of cell numbers reduces variance near the end of exponential growth, but this may be obscured by subsequent increase in cell size. In contrast with earlier studies, we find that targeted growth reduces both genetically and environmentally determined differences among early growth trajectories. Final size may be determined by an antagonistic balance between early growth rate and age at initiation of puberty.     

Genetic complementation between mutant b subunits in F1F0 ATP synthase

In Escherichia coli, a parallel homodimer of identical b subunits constitutes the peripheral stalk of F(1)F(0) ATP synthase. Although the two b subunits have long been viewed as a single functional unit, the asymmetric nature of the enzyme complex suggested that the functional roles of each b subunit should not necessarily be considered equivalent. Previous mutagenesis studies of the peripheral stalk suffered from the fact that mutations in the uncF(b) gene affected both of the b subunits. We developed a system to express and study F(1)F(0) ATP synthase complexes containing two different b subunits. Two mutations already known to inactivate the F(1)F(0) ATP synthase complex have been studied using this experimental system. An evolutionarily conserved arginine, b(Arg-36), was known to be crucial for F(1)F(0) ATP synthase function, and the last four C-terminal amino acids had been shown to be important for enzyme assembly. Experiments expressing one of the mutants with a wild type b subunit demonstrated the presence of heterodimers in F(1)F(0) ATP synthase complexes. Activity assays suggested that the heterodimeric F(1)F(0) complexes were functional. When the two defective b subunits were expressed together and in the absence of any wild type b subunit, an active F(1)F(0) ATP synthase complex was assembled. This mutual complementation between fully defective b subunits indicated that each of the two b subunits makes a unique contribution to the functions of the peripheral stalk, such that one mutant b subunit is making up for what the other is lacking.     

红壳色文蛤F1代养殖群体多样性分析

运用形态学标记和分子标记对江苏省文蛤良种场红壳色文蛤F1代养殖群体(父母本为江苏野生红壳色群体)进行遗传多样性分析。用文蛤壳长、壳宽、壳高和体重4个可量性状进行形态学数据的聚类分析,显示可量性状变异系数在38.48%-82.95%。运用7个引物微卫星基因座的多态性进行了养殖群体F1代的分子标记评估,结果表明,7个微卫星基因位点的平均等位基因数3.857 1,平均有效等位基因数2.583 0,平均观察杂合度0.565 3,平均期望杂合度0.565 3,Shannon指数平均数1.050 1,多态信息含量平均数0.522 5。综合形态学数据和分子标记的研究结果表明,红壳色文蛤江苏养殖群体F1代的遗传多样性处于中度偏高水平,具有较高的遗传改良潜力。     

Effects of paternal ethylene dibromide exposure on F1 generation behavior in the rat

The effects of ethylene dibromide (EDB) exposure to the male rat were studied through behavioral assessments of their F1 progeny. Exposed males were bred with untreated female rats at 4 or 9 weeks after 5 daily EDB treatments. Behavioral assessment of motor reflexes and motor coordination were examined up to 21 days of age. Significant differences in the development of motor coordination and motor activity were observed in the F1 progeny of EDB-exposed males. These results support the evidence of EDB genotoxicity and further demonstrates the utility of behavioral end-points of the offspring as a sensitive means of assessing paternal reproductive risk.