树木发育阶段理论及其在橡胶树育种中的应用(综述)

近一个多世纪来,树木发育阶段理论的应用研究取得了令人瞩目的成就,在果树育种,造林,园艺等领域得到广泛应用并取得了巨大的经济效益,与此形成鲜明对比的是,树木发育阶段理论研究的核心内容如发育阶段转变的遗传基础,分子机制等方面的基础研究工作却进展缓慢,对各个阶段的发育特性和利用潜力认识不足,在一定程度上限制了该理论在生产实践中的应用和推广范围,本文就树木发育阶段理论的研究现状,存在问题及在橡胶树育种中的应用等进行了综述和探讨。     

树木复幼的研究概述

幼龄树木通常具有良好的生根能力、旺盛和通直的生长习性与较强的抗性, 然而随着树木的成熟这些特性会逐渐丧失。复幼是使成熟树木重现某些幼态性状的过程。成熟树木的复幼和幼态保持是林木生产、无性繁殖、遗传改良和生物技术在林木中应用中十分重要的科学问题。本文对树木的组织和器官保持幼态的特性、顶端分生组织表达幼态的潜能、与复幼相关的生理、生化和分子生物学以及复幼方法等方面的研究进行了概述, 并对今后的研究和需要解决的关键问题提出了意见和建议。     

树木复幼的研究概述

幼龄树木通常具有良好的生根能力、旺盛和通直的生长习性与较强的抗性,然而随着树木的成熟这些特性会逐渐丧失.复幼是使成熟树木重现某些幼态性状的过程.成熟树木的复幼和幼态保持是林木生产、无性繁殖、遗传改良和生物技术在林木中应用中十分重要的科学问题.本文对树木的组织和器官保持幼态的特性、顶端分生组织表达幼态的潜能、与复幼相关的生理、生化和分子生物学以及复幼方法等方面的研究进行了概述,并对今后的研究和需要解决的关键问题提出了意见和建议.     

植物激素效应启动子

植物激素调节植物细胞的伸长、分裂和分化,并且控制植物体的生长、发育、休眠、萌发、生根、开花、结果以及果实成熟等过程。自30年代以来,人们一直不停地研究植物激素,近年来关于植物激素效应启动子的研究报道迅速增多。尽管不同植物基因的启动子间存在一定差异,但都具有基本的启动子核心序列,基本启动子含有转录起始位点和位于-25～-30的ＴＡＴＡ盒,ＴＡＴＡ盒的序列为ＴＡＴＡ[Ａ/Ｔ]Ａ[Ａ/Ｔ],转录起始点一般为Ａ。除基本启动子外,植物激素效应基因的启动子中还存在一些顺式调节元件,这些顺式调节元件在对不同植物激素产生效应的基因收…     

植物激素研究中的化学生物学思路与应用

植物激素是植物生长发育过程中必不可少的重要调节物质, 它们直接或间接参与调控从种子萌发到成熟的各个发育阶段以及对生物/非生物胁迫的响应。随着利用小分子化合物探究生物体生理代谢分子机制的不断发展, 植物生物学与化学之间一个新的前沿交叉学科——化学生物学随之诞生, 并在短时间内取得了重要进展。化学生物学的思路与方法在植物激素研究领域中起到了不可替代的作用, 尤其是在激素合成及信号转导研究领域。该文概述了主要植物激素的小分子类似物及其在植物生长发育和生物/非生物胁迫响应等方面的作用机制, 并讨论了激素类似物在实际生产中的应用潜力及未来的研究方向。     

植物激素研究中的化学生物学思路与应用

植物激素是植物生长发育过程中必不可少的重要调节物质,它们直接或间接参与调控从种子萌发到成熟的各个发育阶段以及对生物/非生物胁迫的响应。随着利用小分子化合物探究生物体生理代谢分子机制的不断发展,植物生物学与化学之间一个新的前沿交叉学科——化学生物学随之诞生,并在短时间内取得了重要进展。化学生物学的思路与方法在植物激素研究领域中起到了不可替代的作用,尤其是在激素合成及信号转导研究领域。该文概述了主要植物激素的小分子类似物及其在植物生长发育和生物/非生物胁迫响应等方面的作用机制,并讨论了激素类似物在实际生产中的应用潜力及未来的研究方向。     

14-3-3蛋白对植物发育的调控作用

14-3-3蛋白是高度保守并在真核生物中普遍存在的一类调节蛋白。不同的14-3-3蛋白同工型具有不同的细胞特异性, 并通过识别特异的磷酸化序列与靶蛋白相互作用, 被称为蛋白质与蛋白质相互作用的桥梁蛋白。在植物生长发育过程中, 14-3-3蛋白通过与其它蛋白的相互作用参与多种植物激素信号转导、各种代谢调控、物质运输和光信号应答等调控过程。该文主要对近年来有关14-3-3蛋白在植物生长发育中的调控作用, 特别是14-3-3蛋白参与调控植物激素信号转导等方面的研究进展进行综述。     

全基因组分析杨树WOX基因家族在茎部发育中的作用

WUSCHEL-related homeobox(WOX)家族是植物特有的转录因子家族,参与分生组织细胞分裂分化、初生和次生物质代谢及植物激素信号转导等多个发育过程,目前尚未有从全基因组分析该基因家族参与杨树茎部发育的相关研究。本项研究旨在对杨树WOX基因家族进行鉴定,在杨树基因中发现18个WOX候选基因,将这些候选基因分为三组,同一分组的大多数WOX家族成员具有相似的基因结构和保守的基序。根据不同发育阶段茎部转录组数据,系统分析了WOX家族成员在茎部不同发育阶段的特异表达情况,并采用qRT-PCR对上述结果进行了验证。结果表明,杨树WOX基因家族在茎部不同发育阶段表现出不同的表达模式,为毛果杨WOX家族的功能研究与利用奠定基础。     

丽江云杉体胚发生过程差异蛋白分析

以丽江云杉非胚性愈伤组织、胚性愈伤组织以及体胚发育过程的球型胚、鱼雷胚和子叶胚培养物为材料,采用双向电泳技术对体胚发生过程中特异表达蛋白进行分析.结果表明,丽江云杉非胚性、胚性愈伤组织及不同发育阶段体胚的蛋白质种类丰富(1 857-2 344个),胚性愈伤及发育体胚蛋白种类多于非胚性愈伤,球型胚蛋白种类最为丰富(2 344个).非胚性、愈伤组织及各发育阶段体胚共检测到44个差异表达蛋白,它们有明显的变化特点,子叶胚阶段的差异蛋白变化最为显著(23个,占特异蛋白总数的52.3％),鱼雷胚新出现大比例的分子量小于30 kD、pI为6.0左右的弱酸性小分子量特异蛋白(8个,占此阶段特异蛋白总数的88.9％),这些体胚发育晚期特异表达蛋白可能与体胚形态建成有密切关系.     

转录中介体复合物(Mediator complex)调控茉莉酸信号途径的新机制

转录中介体(Mediator)是由多个在进化上高度保守的亚基组成的蛋白复合物。在基因转录过程中,转录中介体分别与基因特异的转录因子和RNA聚合酶II相互作用,广泛参与二者之间的信息传递,被称为真核生物基因转录的中央控制器。在植物激素信号转导研究中,人们主要关注激素特异的转录因子的作用,但对于转录中介体的功能及作用机理     

Proteomic analysis of the potato tuber life cycle

The tuber of potato (Solanum tuberosum) is commonly used as a model for underground storage organs. In this study, changes in the proteome were followed from tuberization, through tuber development and storage into the sprouting phase. Data interrogation using principal component analysis was able to clearly discriminate between the various stages of the tuber life cycle. Moreover, five well-defined protein expression patterns were found by hierarchical clustering. Altogether 150 proteins showing highly significant differences in abundance between specific stages in the life cycle were highlighted; 59 of these were identified. In addition, 50 proteins with smaller changes in abundance were identified, including several novel proteins. Most noticeably, the development process was characterized by the accumulation of the major storage protein patatin isoforms and enzymes involved in disease and defense reactions. Furthermore, enzymes involved in carbohydrate and energy metabolism and protein processing were associated with development but decreased during tuber maturation. These results represent the first comprehensive picture of many proteins involved in the tuber development and physiology.     

Pattern of mineral uptake in the developing human deciduous enamel

The present study describes the detailed changes in mineral concentration in developing human enamel across the different stages of development from early formation to maturation. The results indicate a stage in the development of deciduous human incisor enamel in which the tissue becomes porous because of a loss of matrix protein, which is subsequently replaced by mineral during the maturation process, with the enamel finally becoming fully mineralized and hard. The importance of this stage with regard to enamel susceptibility to metabolic influences is discussed.     

Label-free shotgun proteomics and metabolite analysis reveal a significant metabolic shift during citrus fruit development

Label-free LC-MS/MS-based shot-gun proteomics was used to quantify the differential protein synthesis and metabolite profiling in order to assess metabolic changes during the development of citrus fruits. Our results suggested the occurrence of a metabolic change during citrus fruit maturation, where the organic acid and amino acid accumulation seen during the early stages of development shifted into sugar synthesis during the later stage of citrus fruit development. The expression of invertases remained unchanged, while an invertase inhibitor was up-regulated towards maturation. The increased expression of sucrose-phosphate synthase and sucrose-6-phosphate phosphatase and the rapid sugar accumulation suggest that sucrose is also being synthesized in citrus juice sac cells during the later stage of fruit development.     

Physiological and morphological characteristics during development of pedunculate oak (Quercus robur L.) zygotic embryos

The developmental stages of oak zygotic embryos (ZEs) are characterized here according to morphological and physiological features. Seeds were harvested from June to September in 1-week intervals. Excised embryos were classified into four stages of development by using growth parameters. For physiological characterization, endogenous levels of abscisic acid (ABA), indole-3-acetic acid (IAA), l-proline, starch content and water status were determined. The expression of the oak legumin storage protein gene was tested in immature cotyledonary ZEs before and after ABA treatment. The ABA levels of the embryos showed a significant peak during the intermediate stage of maturation (stage III) and then decreased again at the end of the late maturation phase (stage IV). Concomitant with ABA, the moisture content declined with the maximum embryo size. High IAA levels were found at the beginning of embryo enlargement as exponential growth occurred (stage II) but decreased during further development. Starch accumulated gradually in the course of maturation, whereas significant values were found in stage IV ZEs near shedding. Proline, on fresh weight basis, was high during stages I and II. Osmotic potential increased when, by rapid dry matter accumulation, stage II ZEs reached their maximum size during early intermediate development. Expression of precocious germination was higher on hormone-free medium, in particular, among stage II and stage III ZEs. Variations in phytohormone levels in combination with changes in tissue water status seem to be important factors for oak ZE development.     

Effects of protein synthesis on maturation, sperm penetration, and pronuclear development in porcine oocytes.

In vitro matured porcine oocytes were used to test the importance of protein synthesis for sperm penetration, the second meiotic division, and pronuclear development. Experiments were carried out to measure rates of protein synthesis in the presence of protein synthesis inhibitors (35 microM or 350 microM cycloheximide or a combination of inhibitors) (study 1); to test for sperm penetration and pronuclear development when protein synthesis was inhibited during fertilization (study 2); to test for oocyte meiosis, sperm penetration, and female and male pronuclear development when protein synthesis was inhibited during maturation (oocyte maturation in vitro with addition of inhibitor at 0, 24, or 36 hr of culture) (study 3); and to analyze the changes in the pattern of protein synthesis during these phases. Sperm penetration, oocyte meiosis, and female pronuclear development were not affected by the total inhibition of protein synthesis during fertilization. By contrast, inhibiting protein synthesis during maturation severely impaired the completion of meiosis and pronuclear development. Although inhibition of protein synthesis after 36 hr of maturation culture did not totally block male pronuclear development (MPN), the rate of MPN formation was lower than for controls (52% vs. 72%, P less than 0.05). However, protein synthesis was absolutely essential between 24 and 36 hr for the formation of MPN after decondensation. This period of maturation coincided with the dominant phase of protein reprogramming in the oocyte.     

Role of ABA in Maturation of Rapeseed Embryos

Development of Brassica napus L. cv Tower embryos of different ages cultured in vitro with and without abscisic acid (ABA) was compared with normal development in situ to investigate the role of ABA in embryo maturation. Endogenous ABA levels were measured by radioimmunoassay, and sensitivity to ABA was assayed in terms of its ability to suppress precocious germination and stimulate accumulation of storage protein and storage protein mRNA. During development in situ, the levels of endogenous ABA and 12S storage protein mRNA both reach their peaks just before the embryos begin to desiccate. The ABA levels during this phase of development also correlate with the time required in culture before germination is evident. Following these peaks, increasing concentrations of exogenous ABA are required to both suppress germination and continue storage protein accumulation in vitro. Thus, both endogenous ABA and ABA sensitivity decline during maturation. The concentrations of exogenous ABA required to suppress germination at these later stages result in abnormally high levels of endogenous ABA and appear to be toxic. These results are consistent with the hypothesis that in maturing rapeseeds, low water content rather than ABA prevents germination during the later stages of development.     

Nuclear-cytoplasmic interactions during ovine oocyte maturation

The present studies have been undertaken to investigate the interactions that occur between the nucleus and cytoplasm of ovine oocytes at various stages during meiotic maturation. We report that the nucleus of ovine fully grown dictyate stage oocytes can be efficiently removed by a microsurgical enucleation procedure. It is demonstrated that between the initiation of maturation and germinal vesicle breakdown certain newly synthesized polypeptides are selectively sequestered in the oocyte nucleus and the major sequestered polypeptide has a relative molecular mass of 28,000, which represent at least 9% of the total labelled polypeptides transferred to the oocyte nucleus during the first 4 h of maturation. The experiments provide evidence that the removal of the oocyte nucleus at various times before germinal vesicle breakdown (GVBD) does not prevent the major series of changes in protein synthesis that occurs after entry into a metaphase. We conclude therefore that the mixing of the nucleoplasm and cytoplasm is not essential for the initiation or progression of the protein reprogramming process during maturation. In addition, the experiments show that the development of the ability to condense chromatin during ovine oocyte maturation is independent of the oocyte nucleus. The combined results strongly support the hypothesis that the extensive series of translational changes that occur in oocytes during maturation are controlled by cytoplasmic rather than nuclear factors.     

Co-ordinated programme of gene expression during asexual intraerythrocytic development of the human malaria parasite Plasmodium falciparum revealed by microarray analysis

Plasmodium falciparum is a protozoan parasite responsible for the most severe forms of human malaria. All the clinical symptoms and pathological changes seen during human infection are caused by the asexual blood stages of Plasmodium. Within host red blood cells, the parasite undergoes enormous developmental changes during its maturation. In order to analyse the expression of genes during intraerythrocytic development, DNA microarrays were constructed and probed with stage-specific cDNA. Developmental upregulation of specific mRNAs was found to cluster into functional groups and revealed a co-ordinated programme of gene expression. Those involved in protein synthesis (ribosomal proteins, translation factors) peaked early in development, followed by those involved in metabolism, most dramatically glycolysis genes. Adhesion/invasion genes were turned on later in the maturation process. At the end of intraerythrocytic development (late schizogony), there was a general shut-off of gene expression, although a small set of genes, including a number of protein kinases, were turned on at this stage. Nearly all genes showed some regulation over the course of development. A handful of genes remained constant and should be useful for normalizing mRNA levels between stages. These data will facilitate functional analysis of the P. falciparum genome and will help to identify genes with a critical role in parasite progression and multiplication in the human host.     

Spermiogenesis and chromatin condensation in the common tree shrew, <Emphasis Type="Italic">Tupaia glis</Emphasis>

We have investigated the cellular characteristics, especially chromatin condensation and the basic nuclear protein profile, during spermiogenesis in the common tree shrew, Tupaia glis. Spermatids could be classified into Golgi phase, cap phase, acrosome phase, and maturation phase. During the Golgi phase, chromatin was composed of 10-nm and 30-nm fibers with few 50-nm to 60-nm knobby fibers. The latter were then transformed into 70-nm knobby fibers during the cap phase. In the acrosome phase, all fibers were packed into the highest-order knobby fibers, each about 80–100 nm in width. These chromatin fibers became tightly packed in the maturation phase. In a mature spermatozoon, the discoid-shaped head was occupied by the acrosome and completely condensed chromatin. H3, the core histone, was detected by immunostaining in all nuclei of germ cell stages, except in spermatid steps 15–16 and spermatozoa. Protamine, the basic nuclear protein causing the tight packing of sperm chromatin, was detected by immunofluorescence in the nuclei of spermatids at steps 12–16 and spermatozoa. Cross-immunoreactivity of T. glis H3 and protamine to those of primates suggests the evolutionary resemblance of these nuclear basic proteins in primate germ cells. This work was supported by the Thailand Research Fund (Senior Research Fellowship to Prof. Prasert Sobhon).