The relationship of differential expression of genes in GA biosynthesis and response pathways with heterosis of plant height in a wheat diallel cross

Heterosis in internode elongation and plant height is commonly observed in hybrid plants, but the molecular basis for the increased internode elongation in hybrids is unknown. In this study, midparent heterosis in plant height was determined in a wheat diallel cross involving 16 hybrids and 8 parents, and real-time PCR was used to analyze alterations in gene expression between hybrids and parents. Significant heterosis of plant height and the first internode in length were observed for all 16 hybrids, but the magnitude of heterosis was variable for different cross combinations. Analysis revealed that the heterosis of the first internode was significantly correlated to that of plant height （r = 0.56, P 〈 0.05）, suggesting that the increased elongation of the first internode is the major contributor to the heterosis in plant height. Real-time PCR analysis exhibited that significant difference in heterosis of gene ex- pression was observed among all cross combinations. Moreover, heterosis of the first internode in length was correlated significantly and positively with expression heterosis of KS, GA3ox2-1, GA20ox2, GA20ox1D, GA-MYB and GID1-1, but significantly and negatively with expression heterosis of GAI and GA2ox-1, which is consistent with our recently proposed model of GAs and heterosis in wheat plant height, suggesting the alteration of GA biosynthesis and response pathways might be responsible for the observed heterosis in plant height.     

黄瓜亲本间分子遗传距离与杂种优势的相关性

选用10个黄瓜亲本,通过RAPD分析计算其分子遗传距离,然后配制遗传距离大,中,小的杂交组合15个,田间测定它们的16个园艺性状,对所得园艺性状数据进行统计分析,并计算园艺性状与分子遗传距离间各种相关曲线的相关系数,结果发现,黄瓜园艺性状与分子遗传距离间的各种相关曲线中,以抛物线的相关系数最优,其中座瓜率,收获始期与分子遗传距离的抛物线相关系数存在着显著相关性。     

Relationship between differential gene expression patterns in functional leaves of maize (<Emphasis Type="Italic">Zea mays</Emphasis> L.) at milk filling stage and heterosis using cDNA-AFLP

To understand the molecular mechanism of maize heterosis ,differential gene expression patterns in the functional leaves of 35 maize hybrids relative to their parents involving 10 elite inbreds at milk filling stage were analyzed hy using cDNA-AFLP,the correlation analyses of various differential expression patterns with the performance and heterosis of main maize agronomic traits were evaluated.The main results were as follows:For uniparental specific expression ,significant positive correlations were detected with the performance of seed weight per ear and 100-seed weight at 0.01 and 0.05 probability levels respectively.For biparental specific expression ,significant negative correlations were detected with the performance of ear diameter and seed weight per ear at 0.01 probability level .For uniparental specific expression ,significant positive correlations were detected with the heterosis of ear diameter and seed weight per ear at 0.01 and 0.05 probability levls rspectively,For biparental specific expression .significant negtive correlation was detected with theheterosis of ear diameter at 0.05 probability level ,However,for F1-spectific expression,for fragments detected only in one parent and F1,and for fragments detected only in two parents or only in F1,no significant correlation was detected with the performance or heterosis of all agronomic traits surveyed.     

Isolation and cloning of a new gene encoding maize initiation factor

It was demonstrated that parental gene expression of maize in hybrid genetic background was different from that in their inbred lines. RT-PCR revealed a cDNA overexpressed in hybrid maize. The cDNA was reamplified and used to screen a corresponding cDNA library. A full length of a cDNA insert ZH01 was isolated and shown to have an open reading frame encoding 414a. a. Sequence comparison shows that ZH01 has extremely high similarity with the previously reported plant initiator factor elF-4A and distinct difference from another maize elF-4A gene MIF4A. Ovcrexpression of ZH01 in hybrid may involve vigorous growth of hybrid maize seedlings.     

Relationship between differ- ential gene expression pat- terns in functional leaves of maize (Zea mays L.) at milk filling stage and heterosis using cDNA-AFLP

The genetic mechanism of heterosis has been one of the most challenging subjects in life science since the 20th century. However, because of the complexity of its genetic basis and the limitations of research methods and means, there was no substantial progress in the research of heterosis from the beginning of the 20th century to the 1990s. The development in molecular biology and bio- technology, especially that in quantitative trait loci (QTL) mapping methods, has made it possible to resea…     

Cloning of a down-regulated gene encoding small GTP binding protein in hybrid wheat

Previous studies showed that differential gene expression between wheathybrids and their parents was responsible for the heterosis. To provide an insight into the molecular basis of wheat heterosis, one cDNA, designated TaRab, was identified from the cDNA library of wheat seedling leaves. The sequence comparison in GenBank revealed that TaRab is homologous to a group of genes encoding Rab-GTP binding protein. Semi-quantitative RT-PCR analysis indicated that TaRab was expressed in all plant tissues examined, but at slightly higher level in leaves. Further analysis exhibited that TaRab displayed lower expression in hybrid than in its patents in both roots and leaves, which was in agreement with the original results of suppression subtractive hybridization. TaRab was located on chromosome 7B and C-7DS5-0.36 by in silico mapping. The relationship between differential expression of TaRab and the molecular basis of wheat heterosis was also discussed.     

Comparative growth and viability of hybrids between two populations of Chinese shrimp （Fennropenaeus chinensis）

The total yield of shrimp farming industry declined after WSSV broke out. It was only at the last 20 years that production had again begun to increase[1]. So far, shrimp farming industries mostly depend on capturing wild shrimps or wild post-larvae to sto…     

贵州西山系列玉米杂交种SSR标记纯度鉴定的研究

以11个贵州西山系列玉米杂交种及相应的15个亲本自交系为材料,采用SSR（Simple Sequence Repeat）分子标记方法,从60对多态性高的引物中分别筛选了双亲互补型特异引物,并利用特异引物进行玉米杂交种纯度鉴定的检验．     

不同品种果蝇及其杂交后代的RAPD多态性分析

通过果蝇近交系的建立,用ＲＡＰＤ技术研究了不同品种果蝇及其杂交后代的ＤＮＡ多态性。结果表明：（１）近交作为一种育种方法,只要利用得当,得是大于害的,在畜禽育种的某些条件下还是可以采用的;（２）不同品种或系间有特异性的ＲＡＰＤ带;（３）在近交系与它们的杂交后代间的ＲＡＰＤ带中,多数带为正反交子代与双亲均相同或正反交子代与单亲共有的带,但有些带上亲代与子代间存在着擀和量的差异,在质的差异上出现双亲中没     

Study on heterosis of intersubspecies between indica and japonica rice （Oryza sativa L.） using chromosome segment substitution lines

Great heterosis exists in the inter-subspecific crossesbetween indica and japonica rice cultivars[1,2] and the ex-ploitation of this heterosis has long been considered as apromising method to further increase rice yield potential[3].Previous studies indicated that there were large differencesbetween the two subspecies with respect to morphology,isozyme, polymorphism of molecular markers and DNAstructure due to long time genetic differentiation[4,5]. Thosedifferences were identified to be clos…     

陆地棉显性无腺体品系与常规品种间杂种优势利用研究 Ⅲ.杂种优势及其与配合力的相关

以７个显性无腺体陆地棉品系和４个常规品种为材料,按ＮＣⅡ设计,对２８个组合的Ｆ１杂种优势及其与配合力的相关进行了分析。结果表明：杂种Ｆ１具有明显优势,２８个组合所研究的１５个性状全部具有中亲优势,６个性状具有高亲优势,４个性状具有竞争优势;杂种Ｆ１各性状的竞争优势分别与父本、母本一般配合力效应值,父母本一般配合力效应平均值和组合特殊配合力效应值均有不同程度的相关,而以父母本一般配合力效应平均值与竞争优势的相关最密切且稳定。     

马尾松双列杂交亲本遗传距离与杂种生长优势相关性分析

马尾松6×6全双列杂交的不同组合,其11年生子代在生长性状及其杂种优势上均存在较大的差异。对亲本遗传距离与子代杂种优势的相关分析发现:亲本的ISSR遗传距离(0.266 0~0.467 0)与子代树高、胸径等生长性状及其杂种优势表现为显著的线性正相关,遗传距离与正、反交子代材积杂种优势的相关系数分别达到0.601和0.597,表明随着亲本间遗传距离的增大,子代各生长性状的杂种优势将呈线性增加。马尾松亲本遗传距离与子代杂种优势的相关性明显高于遗传距离与子代生长性状的相关性,表明根据亲本遗传距离对子代杂种优势进行预测比直接预测子代生长性状更可靠。根据这一结论,优先选择树高、材积等经济性状优良同时遗传距离较大的杂交亲本,有望提高子代杂种优势幅度并获得材积性状优良的子代。     

Comparison between varietal purity and zymogram purity in maize

The zymogram purity of 5 inbred lines, 7 single cross hybrids and 7 single cross hybrids mixed with their parental lines was examined by a vertical discontinous polyacrylamide gel electrophoresis. Results indicate that the maize hybrid impurity is mainly composed of three parts:mixed with the seeds from parents or other source, contaminated with the seeds resulting from unknown pollination and variable in genetic background. It was found that the varietal purity is higher than the zymogram purity and they showed a linear relationship. The regression mefficient (γ) between varietal purity and zymogram purity is 0.898 2. There is an average of 3.5 % variable in the field. However, using a known rate of the mixed seeds, their regression mefficient is 0.999 9. It was also found that the examinational mix rate is 0.33% higher than the known mix rate. The seedling rate of the single cross hybrids is 85.71 %, but that of hybrids mixed with their parental lines is only 77%. Therefore, it is reasonable to claim that zymogram purity is lower than the varietal purity.     

Genetic basis of heterosis and inbreeding depression in rice （Oryza sativa L.）

The genetic basis of heterosis was studied through mid-parent, standard variety and better parent for 11 quantitative traits in 17 parental lines and their 10 selected hybrids in rice (Oryza sativa L.). The characters were plant height, days to flag leaf initiation, days to first panicle initiation, days to 100% flowering, panicle length, flag leaf length, days to maturity, number of fertile spikelet/panicle, number of effective tillers/hill, grain yield/10-hill, and 1000-grain weight. In general the hybrids performed significantly better than the respective parents. Significant heterosis was observed for most of the studied characters. Among the 10 hybrids, four hybrids viz., 17Ax45R, 25Ax37R, 27Ax39R, 31Ax47R, and 35Ax47R showed highest heterosis in 10-hill grain yield/10-hill. Inbreeding depression of F2 progeny was also studied for 11 characters of 10 hybrids. Both positive and negative inbreeding depression were found in many crosses for the studied characters, but none was found significant. Selection of good parents was found to be the most important for developing high yielding hybrid rice varieties.     

利用玉米受精至籽粒成熟阶段杂种优势,增加单交种的产量潜力

本文依据Ashby提出的玉米从受精作用开始在胚的发育期直至籽粒成熟阶段具有杂种优势的理论,利用胚乳显性标志性状,采用混合授粉方法,对单交种F_1代同一果穗上所结杂交种子和自交种子的平均粒重、单籽粒重进行了测定和统计分析,讨论了利用胚胎阶段杂种优势在生产上增加单交种产量潜力的可能性。