植物数量性状变异的分子基础与QTL克隆研究进展

探讨数量性状变异规律以便对其进行遗传操纵一直是植物遗传学的一个重要领域。DNA分子标记和QTL作图技术的发展以及拟南芥和水稻全基因组测序的完成极大地促进了植物数量性状分子基础的研究。现已克隆了拟南芥ED1、水稻Hdl、玉米Tb1、番茄fw2．2和Brii9-2-5等控制目标数量性状的基因。数量性状表型变异不仅源于多个数量性状基因（QTL）的分离．而且还受到内外环境的修饰。QTL等位基因变异与孟德尔基因变异具有类似的分子基础,即基因表达或蛋白质功能发生改变。通过分析已克隆的植物QTL的变异特征及分子基础,讨论了植物QTL克隆技术策略,并对QTL研究所面临的挑战和应用前景进行了展望。     

我国农作物QTL定位研究的现状和进展

植物大多数重要的经济性状都是数量性状,研究植物数量性状遗传对植物育种具有十分重要的意义。近十几年来,分子生物学特别是分子标记技术的飞速发展,许多植物高饱和的分子连锁图谱的构建,使得我们可以更深入地进行数量性状的研究。本文综述了近年来我国在农作物数量性状遗传研究方面的进展及发展动态。列举了我国利用DNA分子标记进行数量性状QTL定位的47个实例。总结了控制数量性状的QTL的数目、类别、效应及其互作和QTL与环境间的互作关系。讨论了当前在该研究领域中存在的问题,展望了该领域的发展前景。     

水稻产量相关QTL研究现状

产量是最为复杂的数量性状,对它的遗传机理了解甚微。近15年来,许多学者利用随机分离群体定位了许多影响水稻产量及其组分的QTL,即以QTL定位的方法对产量潜力进行遗传剖析。试验证明上位性效应对产量及其组分性状遗传变异起着重要作用,但目前大多数QTL研究仍侧重于发掘和克隆单个主效QTL,然而对单一基因／QTL的深入了解还不足以诠释复杂性状遗传基础的全貌,还没有为育种家提供足够的可应用于分子标记辅助育种的遗传信息并用于提高水稻产量。笔者认为今后的数量性状研究尚需加强复杂性状QTL遗传网络的发掘,在改良水稻品种性状的同时发展并完善QTL研究。     

水稻QTL分析的研究进展

水稻许多重要的性状是由多基因控制的数量性状,经典的数量遗传学只能把数量性状作为一个整体进行研究。近年来．高密度分子标记连锁图的构建和有效的生物统计学方法的发展使人们对数量性状遗传基础的研究出现了革命性的变化。通过对不同群体内的个体或品系的分子标记基因型和表型数据的共分离分析,能对QTL进行检测和定位。本文对QTL定位的原理和方法进行了介绍,从QTL的数目和效应、上位性效应、QTL基因型与环境的互作、相关性状的QTL以及个体发育不同阶段的QTL等方面对水稻QTL分析的研究进展进行了综述。水稻基因组测序计划已经完成,本文还对基因组时代水稻QTL精细定位和克隆的方法进行了探讨,对QTL分析在水稻育种中的应用前景进行了展望。     

小麦株高性状的QTL分析

自20世纪60年代农林10号矮秆基因被用于小麦育种以来,矮化育种成为世界范围内势不可挡的趋势,矮秆基因研究被越来越多的育种专家重视,先后鉴定出20余个矮秆基因,并应用其中6,7个基因,培育了大批丰产潜力大的半矮秆品种,应用矮秆冬小麦吕系DN3338（♀）和F390（♂）杂交得到的F2：3群体,研究小麦株高的遗传基础,以控制株高的数量性状基因座进行定位,利用240个F2：3家系,构建了含215个微卫星标记,覆盖3600cM,由21个连锁群组成的遗传 连锁图谱,并对该群体进行了4个环境（2年：2000年和2001年,2点：北京和石家庄）3重复的田间种植;采用区间作图法,对该群体的株高性状进行了QTL分析。结果表明：7个影响株高的QTL分别位于染色体1B,4B(2个）,6A（2个）,6D和7A上,每个QTL能解释5．2％－50．1％的表型变异,每个环境条件下检测出的所有QTL能解释64．8％－75％,的表型变异,除了7A上的QTL外,其他6个降低株高的QTL均来自ND3338,其效应介于0．94cm-9.33cm之间,且其中的4个在所有的环境下都能被检测出来,具有较高的稳定性,在4BS的Xgwm113标记附近有一主效QTL,其在不同的环境下能降低株高7．91cm-9.33cm,解释27．8％－36．2％,的表型变异,有着同农林10号中Rht-Blb相近的效应;同时在4BS上还发现一个和地点互作的QTL,该QTL在石家庄的两年试验中均被检测到,且有较大的效应值（80cm和7.6cm),因此,认为大部分的QTL能在所有的环境中检测到,这些QTO可以被用于品种改良和分子标记辅助选择育种。     

我国农作物QTL定位研究的现状和进展

植物大多数重要的经济性状都是数量性状,研究植物数量性状遗传对植物育种具有十分重要的意义。近十几年来,分子生物学特别是分子标记技术的飞速发展,许多植物高饱和的分子连锁图谱的构建,使得我们可以更深入地进行数量性状的研究。本文综述了近年来我国在农作物数量性状遗传研究方面的进展及发展动态。列举了我国利用DNA分子标记进行数量性状QTL定位的47个实例。总结了控制数量性状的QTL的数目、类别、效应及其互作和 QTL与环境间的互作关系。讨论了当前在该研究领域中存在的问题,展望了该领域的发展前 景。     

大白菜部分形态性状的QTL定位与分析

应用352个标记位点的大白菜AFLP和RAPD图谱和一套栽培品种间杂交获得的重组自交系群体,采用复合区间作图的方法对大白菜9个形态性状进行QTL定位及遗传效应研究。在14个连锁群上检测到50个QTL:其中控制株型的QTL有5个;控制株高的QTL有6个;控制开展度的QTL有5个;控制最大叶长的QTL有7个;控制最大叶宽的QTL有4个;控制叶形指数的QTL有6个;控制中肋长的QTL有7个;控制中肋宽的QTL有4个;控制抽苔的QTL有6个。另外,估算了单个QTL的遗传贡献率和加性效应。这将为大白菜品种改良中形态性状的分子标记辅助选择提供理论依据。     

水稻纹枯病抗性QTL分析

对灿稻窄叶青8号（ZYQ8）和粳稻京系17（JX17）以及由它们构建的加倍单倍体（DH）群体,分别在杭州和海南岛,采用注射器接种法进行纹枯病抗性鉴定,并使用该群体的分子链锁图谱进行数量性状座位（QTL）分析。共检测到4个抗纹枯病的QTL（qSBR-2、qSBR-3、qSBR-7和qSBR-11）,分别位于第2、第3、第7和第11染色体。其中qSBR-2、qSBR-3、qSBR-7的抗性基因由抗病亲本ZYQ8贡献,而qSBR-11的抗性基因来自感病亲本JX17。qSBR-2、qSBR-3、qSBR-7在杭州和海南岛都能检测到,而qSBR-11只在杭州检测到。在杭州的实验中,纹枯病病级与秆长和抽穗期呈显著负相关;在控制秆长和抽穗期的QTL中,控制秆长的qCL-3与qSBR-3位于同一染色体区域,其余QTL与抗纹枯病的QTL之间无连锁关系。     

植物QTL定位方法的研究进展

本文系统地介绍了QTL定位的单一标记分析法、区间作图法以及复合区间作图法、混合显性模型的分析方法,概述了一些主要定位方法的分析原理、存在的主要优缺点。单一标记分析法可以采用方差分析、回归分析或似然比检验的方法分析。区间作图法和复合区间作图法是基于两个相邻标记的QTL定位方法,可采用回归分析或最大似然法分析。复合区间作图法在模型中包括了与其他QTL连锁的标记,可以提高作图的精度和效率。混合线性模型的QTL定位方法可以包括复杂的遗传效应及QTL与环境的互作效应,具有更广阔的应用前景。 Abstract:QTL mapping methods are reviewed for single-marker mapping,interval mapping,composite interval mapping,and mixed-model based method.Statistical approaches along with their properties are discussed for the mapping methods.ANOVA,regression method and likelihood ratio test can be applied in single-marker mapping.Interval mapping and composite interval mapping can be conducted,based on two interval markers,by regression method and maximum likelihood method.Since markers linked with other QTLs are include in the model,composite interval mapping is more precision and powerful.Mapping QTL by mixed-model approaches is more applicable when complicated QTL effects as well as QTL by environment interaction are analyzed.     

玉米和水稻重要性状QTL的比较研究

在构建玉米分子标记连锁图和对重要性状进行QTL定位的基础上,以玉米和水稻的分子标记比较图谱为桥梁,分析了控制玉米和水稻F2：3群体重要农艺和产量性状QTL的共线性关系。研究结果表明：在玉米和水稻共线性的染色体区段,控制玉米株高、行数和行粒数的QTL与控制水稻株高、单株有效穗和每穗实粒数的QTL存在广泛的对应关系;在已定位的影响玉米株高等5个性状的45个QTL中,有16个与水稻“汕优63”群体中5个相同或相似性状所定位的38个QTL中的12个具有共线性关系。这一结果为利用水稻的基因组数据来定位、分离和克隆玉米重要性状的QTL提供了有益信息。同时发现,控制水稻某一个性状的QTL常常与控制玉米同一性状的两个QTL相对应,这一结果为玉米染色体是由水稻染色体加倍而来的理论假设提供了支持。研究还发现,不管是玉米还是水稻在染色体上都存在QTL的富集区域,而这些富集区域常常存在于相同的共线性区域,暗示着玉米和水稻控制相同或相似性状的QTL可能有着相同的起源。基于性状的比较基因组研究不但有助于新基因或QTL的发现、克隆和利用,同时还有助于研究不同物种间染色体的演变和进化规律。     

蜜蜂microRNA的研究进展

MicroRNA (miRNA)是一类长度为18~24 nt的内源性非编码小RNA分子,它能通过与靶标mRNA 分子互补结合抑制蛋白质翻译或导致 mRNA 降解,从而调控靶基因表达。蜜蜂是重要的社会性经济昆虫,一直是国际上热门的研究对象。迄今为止,通过各种生物技术在蜜蜂中发现已鉴定注册的miRNA共有218个,对蜜蜂miRNA的研究表明其在蜜蜂的胚胎发育、级型分化、劳动分工和免疫防御等方面可能具有重要的调控作用。本文就miRNA对蜜蜂蜂王和工蜂级型分化、哺育蜂和采集蜂劳动分工、舞蹈行为、脑部神经功能及免疫防御等方面调控作用的最新研究进展进行了综述,以期为进一步研究miRNA提供借鉴和参考。     

Acquisition of a time-memory in forager honey bees

Forager honey bees can associate the time of day with the presence of food at locations outside the hive. It is thought that this time-memory enables the bee to make a spatio-temporal match between its behavior and floral nectar secretion rhythms. Despite a long tradition of research, the mechanisms by which the time-memory becomes established are unknown. We investigated the influences of two experiential factors on the acquisition of time-memory: (1) the number of collecting visits made by the forager within a feeding bout during a restricted time of day and (2) the number of days of exposure to the restricted feeding time. Our results indicate that these two factors control different processes. The number of days of experience influences the temporal accuracy of reconnaissance behavior to the food source. The cumulative number of collecting visits within the feeding bouts has no apparent effect on time-accuracy but, instead, determines the probability of exhibiting food-anticipatory behavior and, if that overt behavior is performed, the intensity of its expression. This paper is dedicated to the memory of Prof. James L. Larimer.     

磁场对蜜蜂行为影响的研究进展

地球内部存在着天然磁性现象,被称为地磁场。当今社会电子通讯发达,电磁波信号频繁,地球表面充满了电磁场。蜜蜂作为重要的授粉昆虫,其活动范围大部分都处于磁场环境中。目前研究者普遍认为蜜蜂能利用磁场进行导航,但环境中异常的磁场同样会影响蜜蜂的定位导航、飞行行为、采集活动和学习认知能力等。本文对前人的研究结果进行了综述,以期系统地了解磁场对蜜蜂行为特性的影响。     

蜜蜂花粉采集器官和采集飞行的线性比例分析

本研究从采粉工蜂飞行中能量消耗相关的几个方面入手,分析了蜜蜂属(Apis) 8个物种的花粉采集器官。结果表明,花粉筐表面积、翅膀表面积、体重及胸部动力容量与蜂种个体的体长呈极显著相关,并且它们随蜂种个体的增大而呈对数线性比例增加。除意大利蜜蜂(A·mellifera ligustica)以外,花粉团重量与花粉筐和基跗节表面积成线性比例。工蜂负重前后重量的变化与花粉筐和翅膀的表面积不成比例[动物学报51 (5) :947 -951 , 2005]。     

Mortality rates of honey bees in the wild

Senescence, defined as an age-specific decrease in physiological performance accompanied by an increase in mortality rate, has been studied in a wide range of animals including social insects. It is not clear, however, whether honey bees in the wild live long enough to exhibit senescent decline. I tested for the effects of senescence on honey bees foraging in natural settings and documented the predicted pattern of exponential increase in mortality rate with forager age. These data indicate that, in spite of high rates of external mortality, senescence is an important factor determining the performance of insects such as honey bees in the wild. Received 16 November 2007; revised 1 February 2008 and 10 March 2008; accepted 18 March 2008.     

Calorimetric investigations of the different castes of honey bees,Apis mellifera carnica

Summary Honey bees of different age and castes were investigated calorimetrically at 20, 25 and 30 °C. Experiments were completed by endoscopic observation of the insects in the visible and the near infrared range and by acoustical monitoring and subsequent frequency analysis of various locomotor activities. Direct calorimetric results of this paper are compared with data of indirect calorimetry from the literature using a respiratory quotient of 1.00 and 21.13 J consumed. Agreements between both methods are generally good. The results show that weight-specific heat production rates increase with age of worker bees by a factor of 5.6 at 30 °C, 3.7 at 25 °C and 40.0 at 20 °C. In groups of foragers the heat production decreases with growing group size to around 6% of the value for an isolated bee. The presence of a fertile queen or of brood reduces the heat output of a small worker group significantly. Adult drones exhibit a much higher metabolic rate (up to 19.7-fold at 20 °C) than juveniles with strong fluctuations in the power-time curves. Fertile queens show a less pronounced heat production rate than virgin queens (54% at 30 °C, 87% at 25 °C and 77% at 20 °C). Calorimetric unrest is much higher for young than for adult queens. Heat production is very low in both uncapped and capped brood and less than 30% of that of a newly emerged worker. In most cases temperature showed a significant influence on the metabolic level, although its sign was not homogeneous between the castes or even within them. Locomotor activities are easily recorded by the acoustic frequency spectrum (0–7.5 kHz) and in good agreement with endoscopic observations and calorimetric traces.Abbreviations RQ respiratory quotient - ww wet weight This paper is part of the PhD thesis of L.F.     

Modeling the potential distribution of the predator of honey bees,Palarus latifrons,in the Arabian deserts using Maxent and GIS

ObjectivesThe species Palarus latifrons (bee pirates) has been recorded in Saudi Arabia as an invasive species. This pest can destroy honey bee colonies under certain conditions. The origin of this species in Africa and it has a good ability to adapt to desert conditions. Studies on this species are very few but its current distribution in the Arabian deserts is mainly in the Arabian Gulf countries. This study presents maps for the possible expansion of this species to invade other desert areas in the Arabian countries’ under current and near-future conditions (2030).MethodsThis pest is a solitary insect with high activity during summer. It is hypothesized that summer conditions and especially temperature are the limiting factor for its distribution in the deserts. The analysis depended on generating maps based on temperatures during summer and based on two bioclimatic factors. Maxent and the geographical information system (GIS) were used to perform the analysis.Results and conclusionsAll maps showed the high ability of this pest to spread in the Gulf countries. In North Africa: south Egypt and Libya, and some parts of Algeria showed suitability for Palarus. The invasion of this pest towards North Africa can happen mostly due to trading activities with Gulf countries especially materials containing soil. Continues monitoring for the activity of Palarus in the risk areas is highly advised.     

Thermal energy conduction in a honey bee comb due to cell-heating bees

Theoretical analysis and numerical calculations are performed to characterize the unsteady two-dimensional conduction of thermal energy in an idealized honey bee comb. The situation explored corresponds to a comb containing a number of brood cells occupied by pupae. These cells are surrounded by other cells containing pollen which, in turn, are surrounded (above) by cells containing honey and (below) by vacant cells containing air. Up to five vacant cells in the brood region can be occupied by cell-heating bees which, through the isometrical contraction of their flight muscles, can generate sufficient energy to raise their body temperatures by a few degrees. In this way, the cell-heating bees alter the heat flux and temperature distributions in the brood region so as to maintain conditions that benefit the pupae. The calculations show that the number of cell-heating bees significantly affects the magnitude, time rate of change, and spatial distribution of temperature throughout the comb. They also reveal a vertically aligned asymmetry in the spatial distribution of temperature that is due to the large heat capacity and thermal conductivity of honey relative to air, whereby air-filled cells experience larger temperature increases than honey-filled cells. Analysis shows that convection and radiation represent negligible modes of thermal energy transfer at all levels in the problem considered. Also, because of its small thickness, the wax wall of a comb cell simultaneously presents negligible resistance to conduction heat transfer normal to it and very large resistance along it. As a consequence the walls of a cell play no thermal role, but simply serve as mechanical supports for the materials they contain.