水稻垩白相关基因及其功能的研究进展

水稻是我国最重要的粮食作物之一,高垩白性状严重降低了稻米的食用与加工品质。水稻的垩白性状主要由遗传控制,并受环境因素的影响。降低稻米的垩白含量是水稻育种改良的重要目标。近年来,研究者们揭示了多个与垩白相关的遗传学机制。本文从能量产生、能量物质分配、淀粉合成和淀粉体堆积结构等途径综述了水稻垩白性状相关基因及其遗传特性的最新研究进展,从而为水稻垩白形成的机理研究与稻米品质遗传改良提供参考。     

水稻垩白的研究现状与改良策略

文章综合分析了水稻垩白与其他稻米品质性状的相关性、垩白形成机理、经典遗传以及分子遗传方面的国内外研究进展。表明垩白形成是一个复杂的生理过程, 与稻株“源-库”关系、籽粒灌浆动态以及胚乳内淀粉的合成与积累密切相关。垩白属于复杂的数量性状, 其遗传具有母体效应、胚乳效应以及细胞质效应, 还受环境条件的影响。在多条染色体上存在一些稳定表达的控制垩白性状的QTL, 其中3个与垩白形成相关的影响淀粉合成、淀粉代谢和果实发育的基因已被克隆。然而, 关于垩白的形成机制和调控网络目前仍不清楚。在育种实践中, 降低垩白仍是我国优质稻育种, 尤其是籼稻品质育种的主要目标之一。文章对今后稻米垩白的遗传研究方向及其改良措施进行了讨论。     

稻米外观品质性状遗传与分子定位研究进展

稻米外观品质主要是指稻米的粒形、垩白、透明度和籽粒色泽等,它不仅直接影响到人们的喜好,还与其他品质性状诸如蒸煮食用、加工等密切相关。因此,外观品质对稻米的商品价值有着十分重要的影响。本文从经典遗传与现代分子生物学两个方面对稻米主要外观品质的遗传研究进展进行了较全面的综述,包括粒长、粒宽、长宽比、粒厚、垩白、透明度和籽粒色泽等。综合近年来的遗传研究结果发现,大多数稻米外观品质性状都是由数量基因控制的。利用分子标记技术已将控制外观品质的QTL（qualitative trait locus）定位在不同的染色体上,为下一步的稻米外观品质改良提供了有利条件。     

水稻品质性状的遗传改良及其关键科学问题

改善稻米品质是水稻遗传改良及基础研究的重要目标。破解控制稻米重要品质性状形成的调控机制,对稻米品质改良和品种选育具有十分重要的意义。近十多年来,稻米品质功能基因组研究成果为其遗传改良提供了丰富的功能基因、有效的功能性分子标记及良好的改良策略。但是,稻米品质本身由多个性状构成,且各品质性状间、品质与产量性状间、品质与环境间均互相影响,极大地限制了稻米品质的遗传改良。因此,文中提出了未来水稻品质性状基础研究及遗传改良的六个关键科学问题。     

研发动态

<正>中科院发现控制水稻粒形和稻米品质的重要基因中国科学院遗传与发育生物学研究所傅向东研究员领导的团队在水稻品质和产量协同遗传改良的研究中取得重要进展,从优质杂交水稻不育系泰丰A中成功分离并克隆了一个控制水稻粒形和提升稻米品质的重要基因GW7。这一基因能通过改变细胞分裂模式,让稻米变得更为细长,有效地减少垩白率和垩白面积,从而提高稻米     

粳稻品质性状间及其与植株性状和产量性状间的遗传相关

利用朱军等提出的种子性状遗传模型,采用 3×3 NCⅡ正反交设计的亲本和部分组合F2代种子,分析了品质性状糙米率、垩白粒率、垩白面积和AC间及上述品质性状与株高、穗部性状等的遗传相关,以期为粳稻育种后代选择提供指导。结果表明,精米重与糙米率存在极显著的母体加性相关;虽然控制品质性状的主要遗传效应分量与植株性状相应遗传效应分量遗传协方差不显著,但在其他相应遗传效应分量方面存在着复杂的关系。     

密穗型水稻品种籽粒垩白性状改良研究

采用籽粒长宽比较大、穗部着粒密的散穗型材料(EG23)改良粳稻密穗型品种的籽粒垩白性状.结果表明,经改良后得到的密穗型品系EA6,与原亲本浙粳20比较,其穗部长度缩短,每穗总粒数增加,着粒密度增大,而籽粒垩白特性得到明显的改善,表明在穗部长度和着粒结构未得到改良的情况下,调节籽粒长宽比对改善密穗型品种籽粒垩白性状具有可能性.穗部不同粒位籽粒垩白性状改良的效果不同,穗顶部和穗中部的改良效果明显优于穗基部.设计的4个不同杂交配组方式中,以反回交配组方式(浙粳20/ EG23//浙粳20)选育效果最好.EA6具有较好的农艺性状,既可作为优异种质资源利用,也可直接应用于生产.这一结果从育种实践上较好地协调了密穗型品种高产与优质的矛盾,对于培育既有密穗型的高产株型又有优良籽粒外观品质的水稻品种具有重要意义.     

沿黄稻区水稻灌浆期遮阴对产量和品质的影响及耐弱光粳稻品种筛选

水稻灌浆期经常遇到阴雨寡照天气,从而导致水稻减产和品质下降。本研究通过分析沿黄稻区近6年水稻灌浆期的气象数据发现,灌浆期日照时数减少是在该时期影响沿黄稻区水稻生产的主要气候因子;以生育期适合沿黄稻区种植的80个粳稻品种为材料,在灌浆期用65%的黑色遮阳网遮阴30 d,检测了水稻冠层顶部晴天、阴天和雨天3种天气下光、温度和湿度等生态环境,分析了灌浆期遮阴对水稻千粒重、加工品质和垩白性状的影响,并进行了耐弱光品种的筛选。结果表明遮阴后水稻冠层顶部阳光在能量和信号两个层面都发生了变化,即辐射量减少和R/FR比值降低;灌浆期遮阴后千粒重降低、糙米率、精米率和整精米率下降、垩白粒率和垩白度增加,其中对千粒重和垩白性状影响最大;以遮阴后千粒重降幅、垩白粒率和垩白度增幅为指标,通过聚类分析从中筛选出了方四落、新丰5号、早香3和小香共4个优质耐弱光品种。     

植酸对稻米品质影响的研究（Ⅰ）

本文报道在水稻生长的抽穗期、齐穗期、灌浆期和蜡熟期喷施不同浓度植酸改良稻米品质的研究。结果表明,在水稻生长的不同阶段,控制喷施植酸浓度可提高糙米率,降低稻米垩白。     

水稻垩白形成的生理和遗传机制

介绍了水稻垩白形成的生理和分子生物学机制的研究进展,提出了垩白形成分子机制研究中的一些难点和期待解决的问题。     

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.     

肝癌中HBV和HCV基因和抗原的分布及意义

采用原位分子杂交方法检测HCV RNA及HBV X基因;采用免疫组织化学方法研究HCV核心抗原,非结构区C33c抗原及HBxAg在肝细胞肝癌中的定位及分布.结果表明(1)HCV RNA、HBV X基因在肝细胞肝癌组织检出率分别为40%(55/136)和82%(112/136).HCV RNA定位于癌细胞的胞浆内,阳性细胞呈散在、灶状及弥漫分布三种形式;HBV X基因在肝癌细胞中的分布呈胞浆型、核型及核浆型,阳性细胞也呈上述三种分布形式;(2)HCV C33c抗原、核心抗原在肝细胞肝癌中的阳性率为81%(133/164)及86%(141/164).C33c抗原定位于癌细胞及肝细胞的胞浆内;核心抗原既定位于癌细胞核中,又可定位于胞浆中.C33c抗原阳性细胞以灶状分布为主;而核心抗原阳性细     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.