植物体细胞胚发生的分子基础

植物通过体细胞胚胎发生途径形成再生植株已是及其普遍的现象,这一发育途径为研究植物细胞的分化、发育、全能性表达和作物品种改良、突变体筛选等提供了良好的实验体系,在理论上和应用中都具重大意义.体细胞分化为胚性细胞是受细胞内外多种因子所调控[1, 2],其中最重要的是受特定基因的调控,在胚性细胞的分化过程中伴随着特定的遗传信息表达,其分化过程的实质是基因按顺序表达调控,是相应基因产物作为胚性细胞形成的分子基础.本文结合我们的工作来探讨体细胞胚发生分子基础研究现状.     

松杉类植物体细胞胚发育机理的研究进展

植物体细胞胚胎发生不仅可作为其繁育的重要手段,而且也是研究胚胎发育过程的一种重要模式系统.体细胞胚在形态和生理上的成熟,直接影响到植株的萌发和再生频率.本文综述了近年来国内外有关裸子植物中几种松杉类植物体细胞胚发育过程的研究报道,其中主要涉及培养基成分和脱落酸(ABA)对体细胞胚发育的影响,以及体细胞胚发育在细胞学、细胞程序性死亡、相关基因和蛋白质组学等方面的研究进展,并进一步讨论了松杉类植物体细胞胚的发育机理,以及体细胞胚在遗传转化系统中的作用.     

植物体细胞胚发生过程中基因表达的研究进展

植物体细胞胚胎发生是一个复杂的发育过程,研究者们通过分析植物体细胞胚发生过程中的基因表达或胚性组织和非胚性组织中基因的差异表达,获得了在体细胞胚发生过程不同时期表达的基因,并分析了这些基因在胚胎发生途径中可能的作用。综述了在植物体细胞胚发生过程中细胞周期相关基因、胁迫和激素应答相关基因、信号转导相关基因、晚期胚胎丰富蛋白基因及与体细胞胚发生相关的胞外蛋白基因表达的研究进展。     

胁迫诱导植物体细胞胚发生中相关基因及蛋白的研究进展

植物体细胞胚发生是一个复杂的发育过程,体细胞胚发生已成为研究植物胚胎发育过程中生理、生化、分子生物学等方面分子机理的模式系统。胁迫被认为是对体细胞胚的诱导有重要作用的因素。植物生长调节物质如2,4-D、ABA等目前认为是与胚性能力获得有关的胁迫物质。在蛋白和转录水平上对基因表达的分析中已鉴定出一些与体细胞胚发生相关的基因和蛋白。该文主要对近年来国内外有关胁迫诱导体细胞胚发生的相关基因及蛋白的研究进展进行综述。     

植物胚胎发生基因调控的研究进展

植物胚胎发生是指单细胞的受精卵经过一系列受控的细胞分裂和分化,发育为成熟的多细胞种胚的过程,也是一个基因有序的选择性表达调控的过程。主要从胚胎发生的3个时期即原胚期——极性建成、球形胚-心形胚过度期——区域形态建成、器官形成与成熟期——分生组织形成及发育等方面对基因调控的研究进展作一简要综述。     

刺五加体细胞胚发生研究进展

综述了国内外对刺五加体细胞胚发生研究的现状。分别对刺五加体细胞胚发生方式、体细胞胚发育相关生理生化变化（包括生长素极性运输、DNA甲基化和代谢途径调控）、体细胞胚生物反应器培养的研究现状进行了评述。     

矮牵牛叶片体细胞胚胎发生发育的组织学观察

以矮牵牛生根试管苗的叶片为外植体,在培养基MS NAA0.1mg/L 6-BA1.6mg/L上诱导体细胞胚胎直接发生。从接种后第一天开始观察叶片愈伤组织发生、发育的外部形态变化,从接种后第七天开始,每隔3天取变化明显的叶片组织块切片观察其胚状体的组织细胞学连续变化。组织切片观察表明,矮牵牛叶片体细胞胚胎发生类似于合子胚的发育过程;矮牵牛体细胞胚起源于叶肉细胞,胚性细胞与非胚性细胞染色明显不同,体细胞胚胎与周边其它组织有明显界线;体细胞胚胎的发育经历胚性细胞、多细胞原胚、球形胚、梨形胚、心形胚、鱼雷胚、类子叶胚等几个阶段。     

植物激素对棉花体细胞胚胎发生的诱导及调节作用

选用11种激素研究了外源激素对棉花胚性愈伤组织增殖、胚胎发生和发育的调控作用。结果表明不同激素对棉花胚性愈伤组织增殖、胚胎发生与发育的影响不同。除2,4-D和BA对棉花胚性愈伤组织的增殖影响不大外,其他激素对棉花胚性愈伤组织的增殖均具有抑制作用,且具有一定的时间效应,同时还受基因型的影响。激素对棉花体细胞胚的形成和发育的影响极大,2,4-D既抑制了体细胞胚的形成,又抑制了体细胞胚的发育;TDZ的作用与2,4-D相似,显抑制了体细胞胚的形成,且诱导获得的体细胞胚均停留在球形胚阶段;GA也抑制了体细胞胚的形成,且不利于体细胞的成熟与萌发;BU-30对棉花体细胞胚形成与发育的影响不大。其他7类生长素类物质和细胞分裂素类物质对棉花体细胞胚的形成均具有促进作用,且依IBA、ABA、IAA、BA、KT、ZT、2iP序增强,其总胚数为对照的1．193—3．852倍;其中2iP的促进作用最大,可使产生的体细胞胚数提高2．852倍。     

大蒜体细胞胚胎发生研究进展

大蒜生产主要靠无性繁殖,因此,进行大蒜体细胞胚发育研究具有重要意义。本文对大蒜体细胞胚发育的影响因子进行了综述,其中较高浓度的维生素B1及还原态氮源可能有利于胚胎发生,而大蒜体细胞内含物则不利于胚胎发生。此外,对大蒜体细胞胚培养中存在的主要问题进行了讨论,并认为系统开展体细胞胚发生的细胞分子生物学机理研究、建立悬浮培养体系以及进行大蒜体细胞胚无性系变异的研究等,具有广阔的前景。     

植物钙信号系统与体细胞胚发生

植物细胞离体培养中的体细胞胚发生受多种内外因素的调控,其中激素对细胞分化,发育和形态建成起着关键的作用。大量研究表明,在激素的作用过程中,Ca^2 信号系统可能是重要的介导者之一。Ca^2 和CaM在植物合子胚和体细胞胚发生中都具有重要作用,其作用机理可能是植物激素通过Ca^2 第二信号系统直接或间接地调控基因表达而实现的。     

脱落酸在植物体细胞胚胎发生中的调控作用

脱落酸是一种具有全面生理功能的植物激素,在植物体细胞胚胎发生发育过程中具有重要的作用。根据国内外最新的研究文献,从脱落酸对植物体细胞胚胎发生的影响、植物体细胞胚胎发生过程中内源脱落酸含量的变化、脱落酸对体细胞胚胎发生过程中基因表达、信号转导的调控和转基因的表达调控入手,概述了脱落酸在植物体细胞胚胎发生中的调控作用。     

Inheritance of somatic embryogenesis and plantlet regeneration from primary (type 1) callus in maize

Summary Genetic factors controlling the differential expression of somatic embryogenesis and plant regeneration of maize from tissue culture were studied in two crosses. Inbred, hybrid, F2 and backcross generations developed from crossing maize inbred A188 with two commercially important inbred maize lines (B73 and Mo17) demonstrated genetic and environmental effects on somatic embryogenesis and plant regeneration when immature zygotic embryos were cultured on MS medium. Additive gene effects were more important in both crosses than dominant gene effects for precent somatic embryogenesis and percent or number of plants regenerated per embryo when generation means were analyzed. In backcross generations of each cross, cytoplasmic, maternal and/or paternal effects were significant for frequency of somatic embryos three weeks after culture as well as frequency, or number of plants regenerated per embryo, nine weeks after culture. Analysis of genetic variances suggests at least one gene (or block of genes) controls the expression of the frequency of somatic embryogenesis in these crosses. Differences in somatic embryogenesis and plant regeneration between B73 and Mo17 are discussed. This is Journal Paper No. 11,435 of the Purdue University Agricultural Experiment Station.     

New insights into plant somatic embryogenesis: an epigenetic view

Somatic embryogenesis plays a significant role in plant regeneration and requires complex cellular, molecular, and biochemical processes for embryo initiation and development associated with plant epigenetics. Epigenetic regulation encompasses many sensitive events and plays a vital role in gene expression through DNA methylation, chromatin remodelling, and small RNAs. Recently, regulation of epigenetic mechanisms has been recognized as the most promising occurrences during somatic embryogenesis in plants. A few reports demonstrated that the level of DNA methylation can alter in embryogenic cells under in vitro environments. Changes or modification in DNA methylation patterns is linked with regulatory mechanisms of various candidate marker genes, involved in the initiation and development of somatic embryogenesis in plants. This review summarizes the current scenario of the role of epigenetic mechanisms as candidate markers during somatic embryogenesis. It also delivers a comprehensive and systematic analysis of more recent discoveries on expression of embryogenic-regulating genes during somatic embryogenesis, epigenetic variation. Biotechnological applications of epigenetics as well as new opportunities or future perspectives in the development of somatic embryogenesis studies are covered. Further research on such strategies may serve as exciting interaction models of epigenetic regulation in plant embryogenesis and designing novel approaches for plant productivity and crop improvement at molecular levels.     

一种新型的棉花体细胞胚胎发生的快速诱导法

用异常苗的茎段和叶片进行培养,可快速高效诱导获得棉花体细胞胚胎发生,激素组膈及其浓度配比影响异常苗的直接胚胎发生,在附加有０．１ｍｇ／Ｌ ＩＡＡ和０．１ｍｇ／ＬＺＴ的改良ＭＳ培养基上,异常苗不仅体细胞胚胎发生率高,而且形成的体细胞胚数目多,用异常苗作外植体获得胚性愈伤组织仅需要时间１０ｄ,获得成熟胚需要２０－３０ｄ,获得再生植株需要６０ｄ,大大短于常规方法获得胚性愈伤组织、体细胞胚和再生植株的时间     

植物体细胞胚胎发生的调控网络

植物体细胞胚胎发生是一个极其复杂而有序的过程,受到多种内外因素的影响与调控。其中基因的表达与调控是影响体细胞胚胎发生最重要和最根本的因素。这些基因包括PLANT GROWTH ACTIVATOR系列基因、LEAFYCOTYLEDON家族基因、BABY BOOM基因、SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASE基因和PICKLE基因等,它们相互作用构成了一个复杂的调控网络。以下结合作者对PLANT GROWTH ACTIVATOR 37等基因的研究,对这一调控网络进行了介绍,并探讨了未来体细胞胚胎发生的研究方向。     

Auxin-induced WUS expression is essential for embryonic stem cell renewal during somatic embryogenesis in Arabidopsis

Somatic embryogenesis requires auxin and establishment of the shoot apical meristem (SAM). WUSCHEL ( WUS ) is critical for stem cell fate determination in the SAM of higher plants. However, regulation of WUS expression by auxin during somatic embryogenesis is poorly understood. Here, we show that expression of several regulatory genes important in zygotic embryogenesis were up-regulated during somatic embryogenesis of Arabidopsis. Interestingly, WUS expression was induced within the embryonic callus at a time when somatic embryos could not be identified morphologically or molecularly. Correct WUS expression, regulated by a defined critical level of exogenous auxin, is essential for somatic embryo induction. Furthermore, it was found that auxin gradients were established in specific regions that could then give rise to somatic embryos. The establishment of auxin gradients was correlated with the induced WUS expression. Moreover, the auxin gradients appear to activate PIN1 polar localization within the embryonic callus. Polarized PIN1 is probably responsible for the observed polar auxin transport and auxin accumulation in the SAM and somatic embryo. Suppression of WUS and PIN1 indicated that both genes are necessary for embryo induction through their regulation of downstream gene expression. Our results reveal that establishment of auxin gradients and PIN1-mediated polar auxin transport are essential for WUS induction and somatic embryogenesis. This study sheds new light on how auxin regulates stem cell formation during somatic embryogenesis.     

Auxin gradients trigger de novo formation of stem cells during somatic embryogenesis

Single or a group of somatic cells could give rise to the whole plant, which require hormones, or plant growth regulators. Although many studies have been done during past years, how hormones specify cell fate during in vitro organogenesis is still unknown. To uncover this mechanism, Arabidopsis somatic embryogenesis has been recognized as a model for studying in vitro plant organogenesis. In this paper, we showed that establishment of auxin gradients within embryonic callus is essential for inducing stem cell formation via PIN1 regulation. This study sheds new light on how hormone regulates stem cell formation during in vitro organogenesis.Key words: auxin gradients, PIN proteins, stem cell, somatic embryogenesis