莱茵衣藻（Chlamydomjonas reinhardtii）sub^cbnⅠ基因的遗传学？…

通过将莱菌衣藻回复合成叶绿素ｂ能力的１４种回复突变株和野生型杂交并对其后代进行四分子分析与随机分析，发现导致回复突变的抑制基因ｓｕｂ位于第一染色体，并根据其连锁程度的不同初步鉴定出５个同功能的非等位ｓｕｂ基因。杂交分析表明ｓｕｂ基因不 专一性，以及在促ｃｂｎⅠ基因重新获得合成叶绿素ｂ的能力的过程中具有单一基因决定性状的特点，不同的ｓｕｂ基因具有其独立的表型效应。ｓｕｂ／Ｓｕｂ杂合二倍体的表型分析证     

餐洗剂对小鼠骨髓细胞SCE形成和Salmonella typhimurium基因回复突变的影响

本研究采用Salmonella typhimurium基因回复突变测试和小鼠骨髓细胞姐妹染色单体交换(SCE)分析,研究了四种餐洗剂及其主要成分LABS、Dispersol D、Alkanolamide的潜在诱变活性。结果表明四种牌号餐洗剂在高浓度时能诱发SCE形成,除TL牌餐洗剂加入S9代谢激活系统后未见诱变作用外,其他三种餐洗剂和三种主要成分都表现出致HisG46和HisD3052基因回复突变的能力。在相当于人日常使用量时,没观察出它们使SCE频率升高的现象,也不表现出致STY基因回复突变的能力。实验还观察了餐洗剂对小鼠骨髓细胞增殖的毒性效应,及其主要成分使细菌菌落异常生长的现象,并讨论了不同诱变效应之间可能存在的关系。     

籼稻品种浙辐802抗瘟性遗传研究

通过与８个日本鉴别品种杂交和利用日本代表菌系研５４－０４及我国南方稻区菌系９５-ｈ接种鉴定,研究了籼稻品种浙辐８０２的抗性遗传。研究结果表明,该品种对菌系研５４-０４的抗性由 ２对显性基因控制,对菌系 ９５-ｔ２的抗性由 １对显性基因控制。基因等位性分析确认,浙辐８０２中抵抗９５－ｔ２的抗病基因与Ｐｉ－ｉ基因等位,与Ｐｉ－ａ、Ｐｉ－ｓｈ、Ｐｉ－ｋ、Ｐｉ－ｚ、Ｐｉ－ｂ、Ｐｉ－ｔ、Ｐｉ－ｔａ等已知基因位点为非等位关系;抵抗菌系研５４－０４,感染菌系９５-ｔ２的基因与Ｐｉ－ｉ、Ｐｉ－ｋ、Ｐｉ－ｂ、 Ｐｉ－ｔ ４个已知基因位点为非等位关系。对这个基因与其他已知基因的等位性进行了分析,认为它可能是１个未被命名的新基因。     

ACC合酶基因（ACSG）可能是黄瓜雌性系的分子标记

利用本实验室根据已知序列分离得到的ＡＣＣ合酶基因（ＡＣＳＧ）为探针对不同黄瓜（Ｃｕｃｕｍｉｓ ｓａｔｉｖｕｓ Ｌ．）品种（系）的基因组ＤＮＡ进行Ｓｏｕｔｈｅｒｎ杂交,初步分析了该基因与黄瓜性别表型之间的相关性。发现在所检测的１０个不同品系中,ＡＣＳＧ与雌性系表型之间存在明显的相关关系,而且这种相关关系在不同的实验中具有良好的重复怀。ＡＣＳＧ基因可能是鉴定黄瓜雌性系的一个分子标记。     

光照和温度对豌豆Lhcb2基因表达的影响

采用ＲＴ－ＰＣＲ技术,从豌豆（Ｐｉｓｕｍ ｓａｔｉｖｕｍ Ｌ．）幼叶中克隆了１个约８００ｂｐ的Ｌｈｃｂ２ ｃＤＮＡ。以特异探针进行的Ｓｏｕｔｈｅｒｎ杂交结果表明,Ｌｈｃｂ２基因以单拷贝形成存在于豌豆基因组中。不同光照时间和温度对豌豆幼苗进行处理的ＲＴ－ＰＣＲ和Ｎｏｒｔｈｅｒｎ ｂｌｏｔｔｉｎｇ分析表明,Ｌｈｃｂ２基因转录水平上的表达受光照的控制,且明显表现出对光照时间的依赖性。光照０￣１．５ｈＬｈ     

稻瘟净（Blasticidin S）脱氨酶基因的克隆

从一株抗稻瘟净（ＢＳ）的Ａｓｐｅｒｇｉｌｌｕｓ ｔｅｒｒｅｕｓ菌中克隆到一个ｂｌａｓｔｉｅｉｄｉｎＳ脱氨酶基因,命名为ｂｓｒＡＳ。ＤＮＡ序列分析表明ｂｓｒＡＳ不含内含子。编码区长３９０ｂｐ,编码１３０个氨基酸。将ｂｓｒＡＳ转化到稻瘟菌中,能使受体菌表达出ＢＳ脱氨酶的活性,从而产生抗药性。该基因可作为抗药标记基因使用,建立稻瘟菌的基因转化系统。     

3个玉米黄叶突变体的光合特性研究

在农业生产中光合作用是作物积累生物量的主要方式,其主要依赖于多种光合色素和完整的叶绿体结构与功能。而玉米叶色突变体对于研究叶绿体发育、提高玉米光合作用能力和产量具有重要意义。以两个玉米自交系郑58(Z58)和B73为对照,对从甲基磺酸乙酯(ethyl methanesulphonate,EMS)处理后的不同玉米诱变群体中筛选到的2株黄叶突变体yl-1(yellow leaf-1,Z58背景)、yl-2(yellow leaf-2,B73背景)以及从玉米自交系Z58中发现的1株自然黄叶突变体yl-3(yellow leaf-3)等3个表型相似的玉米黄叶突变体的形态特征、光合色素含量、叶绿素合成前体物质含量进行了比较研究。结果表明,与对照相比,3个突变体在整个生长周期内均呈现不同程度的黄叶表型、不复绿、植株矮小、发育迟缓;叶片总叶绿素、叶绿素a和叶绿素b含量均显著降低(P<0.05),叶绿素a/叶绿素b比值显著升高(P<0.05);不同突变体的各类叶绿素合成前体物质含量有不同程度的降低。3个突变体的黄叶表型可能是由不同基因的突变导致相关四吡咯化合物合成异常引起的。研究结果为定位...     

水稻幼苗条纹突变体yss1的转录组分析

利用60Co辐射诱变籼稻品种"Ⅱ-32B",筛选得到一个水稻幼苗条纹突变体yss1,该突变体在水稻五叶期前表现出明显的条纹叶表型;色素分析表明yss1叶片中叶绿素和类胡萝卜素含量明显低于野生型,五叶期后突变体和野生型无显著差异。利用转录组分析水稻三叶期野生型和突变体yss1中的基因表达,表明与野生型相比,yss1中表达差异显著的基因432个,其中274个表达上调,158个表达下调。GO分析显示叶绿素合成途径中多数基因表达上调,类胡萝卜素合成过程中的相关基因受到不同程度地调控。因此,推测YSS1基因通过调节叶绿素和类胡萝卜素合成过程中的基因表达,进而调控光合色素的合成。     

水稻叶片叶绿素和过氧化氢含量的QTL检测及上位性分析

研究水稻叶片叶绿素和过氧化氢含量的遗传规律,对探讨光合代谢产物遗传规律和开展高产育种具有重要指导意义。利用由日本晴／Kasalath∥日本晴的杂交组合衍生的98个回交重组自交家系(BC1F9)所组成的BIL(backcross inbred lines)群体,在第1、2、3和10染色体上分别检测出5个与叶绿素含量相关的QTL和2个影响剑叶过氧化氢含量的QTL,其中位于第1染色体的RFLP标记C86和C813之间的q-Chll对叶绿素含量的影响最为显著,对表型变异的贡献率达22％,其增效基因来自粳稻品种日本晴;同时在该区间检测到1个与剑叶过氧化氢含量相关的QTL:q-H2O2I,对过氧化氢含量的减效基因来自日本晴品种。上位性分析结果显示影响叶绿素含量及过氧化氢含量的非等位QTL之间存在显著的上位性效应。具有上位性效应的QTL分布于第2、6、11和12染色体上,未检测到与q-Chll或q-H2O2I互作的位点。暗示日本晴品种的RFLP标记C86和C813之间存在1个能够提高叶绿素含量,同时又能降低过氧化氢含量的主效QTL,其加性效应显著而不存在上位性效应。     

非01群霍乱弧菌溶血素基因的初步研究

本文报导86个不同血清型非01群霍乱弧菌菌株,用含El Tor霍乱弧菌溶血素基因的同位素探针作菌落原位杂交,结果显示其中80个菌株(占93%)具有与El Tor霍乱弧菌溶血素同源性基因;其余6株菌则显示阴性结果,表明不存在这种溶血素基因。但用表型方法测定时,它们都显示有溶血性。此说明非01群霍乱弧菌中存在有不同种溶血素。     

Identification of a vinyl reductase gene for chlorophyll synthesis in Arabidopsis thaliana and implications for the evolution of Prochlorococcus species

Chlorophyll metabolism has been extensively studied with various organisms, and almost all of the chlorophyll biosynthetic genes have been identified in higher plants. However, only the gene for 3,8-divinyl protochlorophyllide a 8-vinyl reductase (DVR), which is indispensable for monovinyl chlorophyll synthesis, has not been identified yet. In this study, we isolated an Arabidopsis thaliana mutant that accumulated divinyl chlorophyll instead of monovinyl chlorophyll by ethyl methanesulfonate mutagenesis. Map-based cloning of this mutant resulted in the identification of a gene (AT5G18660) that shows sequence similarity with isoflavone reductase genes. The mutant phenotype was complemented by the transformation with the wild-type gene. A recombinant protein encoded by AT5G18660 was expressed in Escherichia coli and found to catalyze the conversion of divinyl chlorophyllide to monovinyl chlorophyllide, thereby demonstrating that the gene encodes a functional DVR. DVR is encoded by a single copy gene in the A. thaliana genome. With the identification of DVR, finally all genes required for chlorophyll biosynthesis have been identified in higher plants. Analysis of the complete genome of A. thaliana showed that it has 15 enzymes encoded by 27 genes for chlorophyll biosynthesis from glutamyl-tRNA(glu) to chlorophyll b. Furthermore, identification of the DVR gene helped understanding the evolution of Prochlorococcus marinus, a marine cyanobacterium that is dominant in the open ocean and is uncommon in using divinyl chlorophylls. A DVR homolog was not found in the genome of P. marinus but found in the Synechococcus sp WH8102 genome, which is consistent with the distribution of divinyl chlorophyll in marine cyanobacteria of the genera Prochlorococcus and Synechococcus.     

Analysis of the chlorophyll biosynthetic system in a chlorophyll b-less barley mutant

The chlorophyll b-less barley (Hordeum vulgare L.) mutant chlorina 2807 allelic to the well-known barley mutant chlorina f2 was studied. 5-Aminolevulinic acid at saturating concentration (40 mM) was introduced into postetiolated leaves of the mutant and its wild type, and the protochlorophyllide accumulation in the dark was measured. It was found that the activity of the enzyme system transforming 5-aminolevulinic acid into protochlorophyllide was the same in both types of plants. The activity of esterifying enzymes that catalyze attachment of phytol to chlorophyllide was analyzed by infiltration of exogenous chlorophyllides a and b into etiolated leaves. The reaction was shown to have close rates in the mutant and wild-type plants. In very early stages of greening of etiolated leaves, when the apoproteins of the light-harvesting complexes are not yet formed, appearance of chlorophyll b was clearly recorded in the wild-type plants, while in the mutant chlorina 2807 no indications of chlorophyll b were detected in any stage of greening. On the other hand, in the mutant as well as in the wild type an active reverse conversion of chlorophyll b into chlorophyll a was possible. It is concluded that (a) in the mutant chlorina 2807 the ability of the biosynthetic system to transform 5-aminolevulinic acid to chlorophyll a is fully preserved, (b) in the mutant the enzymes converting chlorophyll a into chlorophyll b are most likely absent or damaged, (c) the conversion of chlorophyll a into chlorophyll b and the reverse conversion of chlorophyll b into chlorophyll a are performed by different enzymes.     

一个番茄EMS叶色黄化突变体的叶绿素含量及光合作用

本试验以测序番茄品种‘Heinz 1706’的甲基磺酸乙酯(EMS)诱变所获得的叶色黄化突变体(Y55)为试材,分析了突变体的植株生长、叶片叶绿素含量及光合参数.结果表明: Y55的株高、茎粗、鲜质量均显著降低;叶绿素 a、叶绿素 b 、类胡萝卜素、总叶绿素含量以及叶绿素 a/b均显著降低,Y55叶绿素合成的前体物质含量均显著低于野生型,尤其是粪卟啉原Ⅲ及其后前体物质;且Y55叶片净光合速率、蒸腾速率、胞间CO₂浓度、气孔导度均显著低于野生型,最大光合速率、CO₂饱和点与补偿点、光饱和点与补偿点也显著下降;Y55的PSII最大量子效率显著降低,F_o显著升高,PSII与PSI的光合电子产量和电子传递速率显著降低;Y55处于基态的捕光色素分子、捕光色素分子处于最低激发态的平均寿命均显著降低.表明粪卟啉原Ⅲ的合成受阻可能是黄化突变体Y55叶绿素含量下降的主要原因,黄化突变降低了叶片捕光色素分子数量,影响了叶片的光合作用,进而抑制了植株的生长发育.     

Defects in the cytochrome b6/f complex prevent light-induced expression of nuclear genes involved in chlorophyll biosynthesis

Mutants with defects in the cytochrome (cyt) b6/f complex were analyzed for their effect on the expression of a subgroup of nuclear genes encoding plastid-localized enzymes participating in chlorophyll biosynthesis. Their defects ranged from complete loss of the cytb6/f complex to point mutations affecting specifically the quinone-binding QO site. In these seven mutants, light induction of the tetrapyrrole biosynthetic genes was either abolished or strongly reduced. In contrast, a normal induction of chlorophyll biosynthesis genes was observed in mutants with defects in photosystem II, photosystem I, or plastocyanin, or in wild-type cells treated with 3-(3'4'-dichlorophenyl)-1,1-dimethylurea or 2,5-dibromo-3-methyl-6-isopropyl benzoquinone. We conclude that the redox state of the plastoquinone pool does not control light induction of these chlorophyll biosynthetic genes. The signal that affects expression of the nuclear genes appears to solely depend on the integrity of the cytb6/f complex QO site. Since light induction of these genes in Chlamydomonas has recently been shown to involve the blue light receptor phototropin, the results suggest that cytb6/f activity regulates a plastid-derived factor required for their expression. This signaling pathway differs from that which regulates state transitions, since mutant stt7, lacking a protein kinase involved in phosphorylation of the light-harvesting complex II, was not altered in the expression of the chlorophyll biosynthetic genes.     

Differential regulation of <Emphasis Type="Italic">chlorophyll a oxygenase</Emphasis> genes in rice

Chlorophyll b is synthesized from chlorophyll a by chlorophyll a oxygenase. We have identified two genes (OsCAO1 and OsCAO2) from the rice genome that are highly homologous to previously studied chlorophyll a oxygenase (CAO) genes. They are positioned in tandem, probably resulting from recent gene duplications. The proteins they encode contain two conserved functional motifs – the Rieske Fe–sulfur coordinating center and a non-heme mononuclear Fe-binding site. OsCAO1 is induced by light and is preferentially expressed in photosynthetic tissues. Its mRNA level decreases when plants are grown in the dark. In contrast, OsCAO2 mRNA levels are higher under dark conditions, and its expression is down-regulated by exposure to light. To elucidate the physiological function of the CAO genes, we have isolated knockout mutant lines tagged by T-DNA or Tos17. Mutant plants containing a T-DNA insertion in the first intron of the OsCAO1 gene have pale green leaves, indicating chlorophyll b deficiency. We have also isolated a pale green mutant with a Tos17 insertion in that OsCAO1 gene. In contrast, OsCAO2 knockout mutant leaves do not differ significantly from the wild type. These results suggest that OsCAO1 plays a major role in chlorophyll b biosynthesis, and that OsCAO2 may function in the dark.     

Characterization and genetic analysis of a light- and temperature-sensitive spotted-leaf mutant in rice

A rice spotted-leaf mutant was isolated from an ethane methyl sulfonate (EMS) -induced IR64 mutant bank. The mutant, designated as spl30 (spotted-leaf30), displayed normal green leaf color under shade but exhibited red-brown lesions under natural summer field conditions. Initiation of the lesions was induced by light and the symptom was enhanced at 33 (°) C relative to 26 (°) C. Histochemical staining did not show cell death around the red-brown lesions. Chlorophyll contents in the mutant were significantly lower than those of the wild type while the ratio of chlorophyll a/b remained the same, indicating that spl30 was impaired in biosynthesis or degradation of chlorophyll. Disease reaction patterns of the mutant to Xanthomonas oryzae pv. oryzae were largely unchanged to most races tested except for a few strains. Genetic analysis showed that the mutation was controlled by a single recessive gene, tentatively named spl30(t), which co-segregated with RM15380 on chromosome 3, and was delimited to a 94 kb region between RM15380 and RM15383. Spl30(t) is likely a novel rice spotted-leaf gene since no other similar genes have been identified near the chromosomal region. The genetic data and recombination populations provided in this study will enable further fine-mapping and cloning of the gene.     

Clp protease controls chlorophyll b synthesis by regulating the level of chlorophyllide a oxygenase

Chlorophyll b is one of the major light-harvesting pigments in green plants and it is essential for optimal light harvesting. Chlorophyll b is synthesized from chlorophyll a by chlorophyllide a oxygenase (CAO) which consists of A, B and C domains. Previously, we demonstrated that the C domain alone has a catalytic function, while the A and B domains control the level of CAO protein in response to chlorophyll b accumulation. We hypothesized that the accumulation of chlorophyll b triggers the proteolytic degradation of CAO. In this study, in order to gain further insight into this regulatory mechanism we screened for mutants that have defects in the control of CAO accumulation. Seeds from a transgenic line of Arabidopsis which overexpressed a CAO-GFP fusion were mutagenized and their progenies were screened by laser-scanning confocal microscopy for mutants showing an elevated level of GFP fluorescence. One particular mutant (dca1) exhibited stronger GFP fluorescence and accumulated a GFP-CAO fusion protein at a higher level. Concomitantly, the chlorophyll a to b ratio decreased in this mutant. The mutation in the dca1 mutant was mapped to the ClpC1 gene, thereby indicating that a chloroplast Clp protease is involved in regulating chlorophyll b biosynthesis through the destabilization of CAO protein in response to the accumulation of chlorophyll b.     

高等植物叶绿素生物合成的研究进展

叶绿素是植物叶绿体内参与光合作用的重要色素,其功能是捕获光能并驱动电子转移到反应中心.整个叶绿素生物合成过程(L-谷氨酰-tRNA→叶绿素a→叶绿素b)需要15步反应,涉及15种酶,迄今在模式植物拟南芥中已分离到27个编码这些酶的基因,完成了以拟南芥为代表的被子植物叶绿素生物合成全部基因的克隆.本文主要对近年来国内外有关植物叶绿素的生物合成过程及相关酶基因的克隆、生物合成途径中2个关键步骤(σ-氨基酮戊酸(ALA)合成和Mg离子插入原卟啉Ⅸ的调节)、影响叶绿素生物合成的主要因素(光、温度、营养元素等),以及叶绿素生物合成相关酶的其他生物学功能等的研究进展进行综述.