籼粳不育新位点的发现及其遗传分析

粳稻０２４２８携有Ｓ－５ｎ广亲和基因,然而与籼稻ＩＲ２４杂交表现为半不育。对０２４２８与ＩＲ２４．Ｐｅｃｏｓ、秋光等品种杂交的分离世代的小穗育性进行遗传分析,结果表明：０２４２８与ＩＲ２４之间的不育性受单基因控制,遗传规律符合单位点孢子体一配子体遗传模式,不育性由非Ｓ－５的新位点引起,美国品种Ｐｅｃｏｓ具有复等位的中性基因;ＲＦＬＰ标记技术检测后初步确定,该新不育位点在第１１染色体上的标记Ｇ２４附件,与目前已报道的不育位点都不等位,新位点暂定名为Ｓ－ｐ（ｔ）。研究结果还显示,粳稻品种秋光与籼稻品种ＩＲ２４之间的不育性受２个不育位点Ｓ－５和Ｓ－ｐ（ｔ）控制,其遗传效应表现有累加作用。     

水稻中大麦Mlo和玉米Hm1抗病基因同源序列的分析和定位

大麦抗病基因Mlo和玉米抗病基因Hm1编码的产物不具有绝大多数植物抗病基因产物所含有的保守结构域。这两个抗病基因的作用机理也不符合基因对基因学说。从水稻中分离克隆了Mlo基因的同源序列OsMlo-1和玉米Hm1基因的同源序列DFR－1。利用水稻分子标记遗传连锁图,将OsMlo-1定位于水稻第六染色体的两俱RZ667和RG424之间;Osmlo-1距离这两个分子标记分别为20．6和6．0cM(centi-Morgan)。将DFR－1定位于水稻第一染色体两个分子标记R2635和RG462之间;DFR－1距离这两个分子标记分别为11．3和23．9cM。参照已发表的水稻分子标记连锁图,发现OsMlo-1和DFR－1的染色体位点分别与两个报道的水稻抗稻瘟病数量性状位点（QTL）有较好的对应关系。结果提示,水稻中与大麦Mlo 和玉米Hml同源的基因可能也参于抗病反应的调控。     

通过和玉米杂交诱导硬粒小麦单倍体

硬粒小麦（Ｔｒｉｔｉｃｕｍ ｄｕｒｕｍ Ｄｅｓｆ．）ＤＲ１４７授以超甜玉米（Ｚｅａ ｍ ａｙｓ Ｌ．） ｓｓ ７７００的花粉后,在８３．４％ 的柱头上观察到花粉萌发及花粉管长入胚囊,有９．９％ 的子房发生了卵细胞的单受精,１．９％ 的子房发生了中央细胞的单受精,３２．７％ 的子房发生了双受精。尽管双受精后可同时形成胚和胚乳,但胚乳往往发育迟缓,甚至败育。硬粒小麦×玉米形成的杂合子核型高度不稳定,在最初的几次细胞分裂中,来自父本玉米的染色体逐步被排除,最后形成硬粒小麦单倍体胚。在授以玉米花粉４ ｈ 后用１００ ｐｐｍ ２,４－Ｄ溶液浸蘸硬粒小麦穗部,可以有效地促进幼胚在缺乏胚乳或胚乳败育情况下的生长和发育。授粉９—１３ ｄ 后由５３３个硬粒小麦子房解剖出２５个胚,得胚率为４．７％ 。通过幼胚拯救获得１１棵正常植株,植株获得率为２．１％ 。根尖细胞染色体计数表明,它们为单倍体（２ｎ＝ ２ｘ＝ １４）。     

两个玉米矮花叶病显性互补抗病基因的发现和定位

玉米矮花叶病是世界普通发生危害严重的玉米病毒病害之一,迄今为止,只有少数几个抗病基因被发现并定位,优良自交系四一是鉴定出定的玉米筹花叶病新抗源,它表现为全生育抗性,通过连续两年的经典遗传学研究发现,四一的成株期抗性表现为一种新的抗病遗传模式,该抗性是由两个显性互补抗病基因控制,87对微卫星标记分析进一步证实了以上推论,并把两个抗病基因分别定位在第三和第六染色体上,第三染色体上的抗病基因与微卫星标记phi029相距14.5cM,第六染色体上的抗病基因与微卫星标记phil26相距7.2cM.     

水稻抗稻瘟病基因Pi-2(t)物理图谱的构建

应用ＢＡＣ文库,采用基于分子标记的染色体着陆（ｍａｒｋｅｒ－ｂａｓｅｄ ｃｈｒｏｍｏｓｏｍｅ ｌａｎｄｉｎｇ）和染色体步查（ｃｈｒｏｍｏｓｏｍｅ ｗａｌｋｉｎｇ）等手段,建立了包含有裟抗稻瘟病基因Ｐｉ－２（ｔ）的物理图谱,该物理图谱由２２个ＢＡＣ克隆组成,遗传跨度８ｃＭ,而物理距离为９２５ｋｂ,该物理图谱的构建不仅为进一步分离和克隆该基因打下了基础,同时也可为分子标记辅助选择育种选择抗稻瘟病新材料     

急性早幼粒细胞白血病（APL）中t（15;17）染色体易位的分子机制研究

对急性早幼粒细胞白血病中ｔ（１５;１７）染色体易位的分子生物学研究显示,１７号染色体上的维甲酸受体α（ＲＡＲＡ）基因与１５号染色体上的ＰＭＬ基因并置,并产生ＰＭＬ－ＲＡＲＡ融合基因。我们以前的工作证明ＡＰＬ患者中ＰＭＬ基因断裂点集中于２个限区域,即ＰＭＬ－ｂｃｒ１和ＰＭＬ－ｂｃｒ ２,二者相距约１０ｋｂ。本文确定了ＰＭＬ－ｂｃｒ １的ＤＮＡ顺序,并确定了一例ＡＰＬ患者染色体相互易位接合部的基本结构     

莜麦与玉米的远缘杂交

莜麦（Ａｖｅｎａ ｎｕｄａ Ｌ．）和玉米（Ｚｅａ ｍ ａｙｓＬ．）杂交有一定的受精率和成胚率。人工传粉后玉米花粉能很快在莜麦柱头上萌发并长入莜麦花柱中,在６８％ 的莜麦花柱中可观察到不只一条玉米花粉管。对授粉后的１６３ 个莜麦子房进行制片观察,发现受精率可达１１．０４％ ,其中只形成胚而无胚乳的卵细胞单受精占３．０７％ ,只形成胚乳而无胚的中央细胞单受精占１．８４％ ,既形成胚又形成胚乳的双受精占６．１３％ 。从授过玉米花粉的大约２２００ 朵莜麦小花中收获１８ 粒种子,对１２ 株实生苗根尖染色体计数表明,其中９ 株为单倍体（２ｎ＝ ２１）,３ 株为二倍体（２ｎ＝ ４２）。结果证明,通过莜麦和玉米杂交后玉米染色体的消除可以获得莜麦单倍体     

水稻半矮秆基因sd－g的染色体定位研究

以标志基因系和ＩＲ３６三体为工具材料,通过杂交,研究了籼稻矮秆材料双矮所携半矮秆基因ｓｄ－ｇ在染色体上的位置。结果表明：半矮秆基因ｓｄ－ｇ与标志基因系Ｍ４所携隐性主基因ｇｈ－１和Ｍ２７所携隐性主基因ｎ１表现连锁。ｓｄ－ｇ与ｇｈ－１之间的交换值为２４．３３％±３．９６％,ｓｄ－ｇ与ｎ１之间的交换值为２９．４４％±４．８１％。由于ｇｈ－１和ｎ１均位于第５染色体,因而推定ｓｄ－ｇ位于第５染色体上。     

籼稻标记性状等基因系的构建

选用涉及水稻(Oryza sativa L．)全部12条染色体的、表现简单遗传且易于识别的形态标记材料27份,以早籼品种浙辐802为轮回亲本,经10余次回交,转育成一套籼型标记等基因系。在此基础上,对同一染色体上的标记进行聚合,育成了15份双标记等基因系。该套材料除所带标记性状外,生育期、株高、分蘖力和穗子大小等主要农艺性状与轮回亲本基本相仿。     

籼稻标记性状等基因系的构建

选用涉及水稻(Oryza sativa L.)全部12条染色体的、表现简单遗传且易于识别的形态标记材料27份,以早籼品种浙辐802为轮回亲本,经10余次回交,转育成一套籼型标记等基因系.在此基础上,对同一染色体上的标记进行聚合,育成了15份双标记等基因系.该套材料除所带标记性状外,生育期、株高、分蘖力和穗子大小等主要农艺性性状与轮回亲本基本相仿.     

Characterization of QTL for oil content in maize kernel

Kernel oil content in maize is a complex quantitative trait. Phenotypic variation in kernel oil content can be dissected into its component traits such as oil metabolism and physical characteristics of the kernel, including embryo size and embryo-to-endosperm weight ratio (EEWR). To characterize quantitative trait loci (QTL) for kernel oil content, a recombinant inbred population derived from a cross between normal line B73 and high-oil line By804 was genotyped using 228 molecular markers and phenotyped for kernel oil content and its component traits [embryo oil content, embryo oil concentration, EEWR, embryo volume, embryo width, embryo length, and embryo width-to-length ratio (EWLR)]. A total of 58 QTL were identified for kernel oil content and its component traits in 26 genomic regions across all chromosomes. Eight main-effect QTL were identified for kernel oil content, embryo oil content, embryo oil concentration, EEWR, embryo weight, and EWLR, each accounting for over 10?% of the phenotypic variation in six genomic regions. Over 90?% of QTL identified for kernel oil content co-localized with QTL for component traits, validating their molecular contribution to kernel oil content. On chromosome 1, the QTL that had the largest effect on kernel oil content (qKO1-1) was associated with embryo width; on chromosome 9, the QTL for kernel oil content (qKO9) was related to EEWR (qEEWR9). Embryo oil concentration and embryo width were identified as the most important component traits controlling the second largest QTL for kernel oil content on chromosome 6 (qKO6) and a minor QTL for kernel oil content on chromosome 5 (qKO5-2), respectively. The dissection of kernel oil QTL will facilitate future cloning and/or functional validation of kernel oil content, and help to elucidate the genetic basis of kernel oil content in maize.     

The ectopic expression of the wheat Puroindoline genes increase germ size and seed oil content in transgenic corn

Plant oil content and composition improvement is a major goal of plant breeding and biotechnology. The Puroindoline a and b (PINA and PINB) proteins together control whether wheat seeds are soft or hard textured and share a similar structure to that of plant non-specific lipid-transfer proteins. Here we transformed corn (Zea mays L.) with the wheat (Triticum aestivum L.) puroindoline genes (Pina and Pinb) to assess their effects upon seed oil content and quality. Pina and Pinb coding sequences were introduced into corn under the control of a corn Ubiquitin promoter. Three Pina/Pinb expression positive transgenic events were evaluated over two growing seasons. The results showed that Pin expression increased germ size significantly without negatively impacting seed size. Germ yield increased 33.8% while total seed oil content was increased by 25.23%. Seed oil content increases were primarily the result of increased germ size. This work indicates that higher oil content corn hybrids having increased food or feed value could be produced via puroindoline expression.     

Recombination in the B Chromosome of Maize to Produce a-B-a Chromosomes

The translocations between the supernumerary B chromosomes and the normal A chromosomes of maize provide a valuable tool for gene localizations, dosage studies and characterization of mutants as null, leaky or gain-of-function. A procedure is described, that relies on recombination in the B chromosome, for marking each of the various B-A translocations with a single dominant marker that will allow dosage classifications of individuals at the mature kernel stage. This marker is R-scm3, which conditions anthocyanin pigment in the aleurone of the endosperm and the scutellum of the embryo. A test for recombination in the B chromosome was conducted by crossing together two translocations, that were broken on opposite sides of the B centromere, and in different A chromosome arms, namely TB-1La and TB-10L18. An example was recovered that linked genetic markers on 1L and 10L to the B centromere. Cytological examination at pachytene of meiosis confirmed the new chromosomal linkage. The use of this procedure to produce a comprehensive set of uniformly marked B-A translocations is discussed.     

Association of endosperm reduction with parental imprinting in maize

Among 38 reciprocal translocations between the maize B chromosome and the proximal region of the long arm of chromosome 10 were six interchanges associated with reduced endosperm development. These six have breakpoints that are the most proximal of the set and constitute a graded series with those broken nearer the centromere which have the most abnormal phenotypes. The group of six defines three major regions that produce the endosperm effects. The remaining 32 translocations reduce kernel size very slightly, suggesting the presence of a fourth region distal to all break-points.-The affected class of kernels lacks a paternally derived representative of that segment of 10L translocated to the B centromeric element (B(10) chromosome; 10 10 B(10)). An accompanying class of kernel in which the paternal B(10) chromosome is duplicated in the endosperm (10 10 10(B) B(10) B(10)) is normal. Kernels of the same endosperm constitution synthesized by introducing both 10 and B(10) maternally, however, are defective, resembling 10 10 10(B). Maternal B(10)'s are therefore unable to compensate for the absence of a paternal B(10). Clearly expression of the 10L genes involved supports normal endosperm growth only following pollen transmission.     

A transposable element insertion within ZmGE2 gene is associated with increase in embryo to endosperm ratio in maize

Most of the maize kernel oil is located in the embryo while the majority of starch is located in the endosperm. Maize kernel composition and value are affected significantly by the ratio of the embryo size to the endosperm size; however, the genetic regulation of embryo to endosperm ratio (EER) in maize is unknown. Here we identified ZmGE2 gene, which encodes a cytochrome p450 protein, as a gene associated with EER variation in maize. We first expressed rice Giant Embryo (GE) gene driven by oleosin promoter in maize and detected a 23.2?% reduction in EER in transgenic seeds, demonstrating the existence of evolutionarily conserved mechanisms for EER determination in rice and maize. We next identified maize GE2, a homolog of rice GE sharing 70?% identity in amino sequence, as a candidate based on the similar expression pattern and co-localization with a previously detected QTL for EER. Followed by linkage and association mapping, a 247-bp transposable element (TE) insertion in 3′-untranslated region of ZmGE2 gene was identified to be associated with increase in EER and kernel oil content. Expression level of the favorable ZmGE2 allele containing the 247-bp TE insertion was strongly reduced. In addition, the 247-bp TE insertion site was a selection target during the artificial long-term selection for the high EER trait in a high oil population. This is the first report that demonstrates an association of ZmGE2 with EER variation in maize and identifies ZmGE2 gene as a promising target for manipulation of EER and grain composition by either transgenic approach or molecular breeding in maize.     

Processing of transgenic corn seed and its effect on the recovery of recombinant beta-glucuronidase

The tools of plant biotechnology that have been developed to improve agronomic traits are now being applied to generate recombinant protein products for the food, feed, and pharmaceutical industry. This study addresses several processing and protein recovery issues that are relevant to utilizing transgenic corn as a protein production system. The gus gene coding for beta-glucuronidase (rGUS) was stably integrated and expressed over four generations. The accumulation level of rGUS reached 0.4% of total extractable protein. Within the kernel, rGUS was preferentially accumulated in the germ even though a constitutive ubiquitin promoter was used to direct gus expression. Fourth-generation transgenic seed was used to investigate the effect of seed processing on the activity and the recovery of rGUS. Transgenic seed containing rGUS could be stored at an ambient temperature for up to two weeks and for at least three months at 10 degrees C without a significant loss of enzyme activity. rGUS exposed to dry heat was more stable in ground than in whole kernels. The enzyme stability was correlated with the moisture loss of the samples during the heating. Transgenic seed was dry-milled, fractionated, and hexane extracted to produce full-fat and defatted germ fractions. The results of the aqueous extraction of rGUS from ground kernels, full-fat germ, and defatted-germ samples revealed that approximately 10 times more rGUS per gram of solids could be extracted from the ground full-fat germ and defatted-germ than from the kernel samples. The extraction of corn oil from ground germ with hot hexane (60 degrees C) did not affect the extractable rGUS activity. rGUS was purified from ground kernels and full-fat germ extracts by ion exchange, hydrophobic interaction, and size exclusion chromatography. Similar purity and yield of rGUS were obtained from both extracts. Biochemical properties of rGUS purified from transgenic corn seed were similar to those of E. coli GUS.     

Linkage and segregation distortion in Drosophila melanogaster

Segregation distortion is caused by a group of genetic elements in and near the centric heterochromatin of chromosome 2 of Drosophila melanogaster. These elements promote their preferential recovery in heterozygous males by rendering sperm bearing the homologous chromosome dysfunctional. Previous work has shown that numerous Y-autosome translocations are associated with the suppression of the segregation distorter phenotype. The present study examined the effects of translocations between the major autosomes upon the expression of segregation distortion. Autosomal translocations involving either the segregation distorter chromosome or its sensitive homologue had no significant effect upon the expression of segregation distortion. These results argue that linkage arrangement per se may not have a major effect on segregation distortion. The suppression of SD by specific Y-autosomal translocations may be due to the disruption of elements on the Y chromosome that are important for the expression of SD.     

Flaxseed Oil for Control of Peanut Rust and Its Disease Control Mechanism

Severity of peanut rust caused by Puccinia arachidis was reduced by 15 edible oils tested. Flaxseed oil was the best suppressing the disease completely. Peanut oil, wheat germ oil, brown rice oil, aloe oil, olive oil and corn germ oil also caused more than 75% reduction in disease incidence. Flaxseed oil reduced the rust to a negligible level in the greenhouse and was nearly as effective as the fungicide chlorothalonil in peanut field trials. The control of peanut rust by flaxseed oil did not result from activation of the host defence mechanisms. Flaxseed oil did not affect urediniospore germination, but reduced the germ tube length and completely suppressed appressorium formation which is essential for the pathogen to form an infection peg to pass through the stomatal aperture and infect the host tissue. Although the pathogen had penetrated, flaxseed oil still exerted some inhibitory effect against the growth of the pathogen. The advantages of using flaxseed oil to control peanut rust are that it is relatively inexpensive, easy to prepare, and friendly to the environment and human health.     

A search for chromosome aberrations induced in mouse spermatogonia by chemical mutagens

Two established chemical mutagens—ethylmethanesulphonate (EMS) and triethylenemelamine (TEM)—were tested for the ability to induce chromosome aberrations in mouse spermatogonia. While not a single aberration was detected following the EMS treatment, a low frequency of translocations and fragments was found in the TEM groups. These findings are in agreement with the data obtained with the specific locus mutation test as applied to male mouse premeiotic germ cells but contrast with the effectiveness of these chemicals in breaking chromosomes in male mouse postmeiotic germ cells. A differential sensitivity of post- and premeiotic germ cells to any kind of genetic damage by these chemical mutagens is most likely to be the correct interpretation of all the data. However, it is also suggested that a high proportion of translocations induced in spermatogonia by chemical mutagens may not be detectable by present methods.