Self-incompatibility in flowering plants: the Brassica model.

Self-incompatibility (SI) is a widespread mechanism in flowering plants that prevents self-fertilization. Self-pollen recognition relies on the products of genes located at the S (self-incompatibility) locus. Significant progress towards understanding molecular interactions allowing stigmatic cells to recognize and reject self-pollen in Brassica has been made during the past two years. Thus, the male and female determinants responsible of the self-incompatibility (SI) response have been identified. The structural features of these molecules strongly suggest that SI response is triggered by a ligand-receptor interaction.     

The molecular biology of self-incompatibility systems in flowering plants

Self-incompatibility is a common mechanism by which flowering plants can exert some control over the process of fertilization. Typically, the self-incompatibility response involves the recognition and rejection of self-incompatible pollen which leads to a block in self-fertilization and, as a consequence, promotes outcrossing. In recent years, considerable progress has been made in the molecular understanding of several self-incompatibility systems. Interestingly, a common mechanism for self-incompatibility is not employed by all flowering plants, but in fact quite diverse mechanisms have been recruited for the rejection of self-incompatible pollen. In this review, the recent advances in the self-incompatibility systems of the Solanaceae, Papaveraceae, and Brassicaceae will be described as well as some of the molecular work that is emerging for the Poaceae and the heteromorphic self-incompatibility systems.     

Photoperiodism dynamics during the domestication and improvement of soybean

Soybean (Glycine max) is a facultative short-day plant with a sensitive photoperiod perception and reaction system, which allows it to adjust its physiological state and gene regulatory networks to seasonal and diurnal changes in environmental conditions. In the past few decades, soybean cultivation has spread from East Asia to areas throughout the world. Biologists and breeders must now confront the challenge of understanding the molecular mechanism of soybean photoperiodism and improving agronomic traits to enable this important crop to adapt to geographical and environmental changes. In this review, we summarize the genetic regulatory network underlying photoperiodic responses in soybean. Genomic and genetic studies have revealed that the circadian clock, in conjunction with the light perception pathways, regulates photoperiodic flowering. Here, we provide an annotated list of 844 candidate flowering genes in soybean, with their putative biological functions. Many photoperiod-related genes have been intensively selected during domestication and crop improvement. Finally, we describe recent progress in engineering photoperiod-responsive genes for improving agronomic traits to enhance geographic adaptation in soybean, as well as future prospects for research on soybean photoperiodic responses.     

观赏植物花期调控途径及其分子机制

开花期控制对观赏植物的生产和应用具有重要意义。目前关于高等植物成花机理的研究已经取得了突破性进展, 为观赏植物花期调控开辟了新途径。该文总结了观赏植物花期调控的途径和方法, 并对改良观赏植物花期的技术思路做了初步分析。通过与高等植物成花机制研究的对比分析发现, 观赏植物开花机理的研究已有了长足发展, 一些观赏植物的转基因研究也取得了丰硕成果。利用分子设计育种途径改良观赏植物的开花期, 突破了传统方法的局限性, 其研究和应用前景非常广阔。     

Maturation of somatic embryos in conifers: Morphogenesis,physiology, biochemistry,and molecular biology

Summary In the past 15 years tremendons progress has been made towards the development of systems for the induction and development of somatic embryos of coniferous species. Since the first report in 1985, several species have been induced to produce somatic embryos. This has been rendered possible by the development of rational media and improvement of culture conditions, which have resulted in increased embryo quality and higher conversion frequency. Understanding the physiological and biochemical events occurring during in vivo embryogenesis has been fundamental in the design of new protocols for improving the somatic embryogenic process. Specifically, the inclusions of abscisic acid (ABA) and osmotic agents, such as polyethylene glycol (PEG), have been shown to be necessary for the functional development of somatic embryos. In the past few years, physiological and biochemical investigations have been useful in increasing our knowledge on the mode of action of ABA and PEG during embryo development. In comparison with the flowering plants, our understanding on the molecular mechanisms regulating the embryogenic process in coniferous species is still very limited. The application of new molecular techniques is therefore fundamental towards this end. The emphasis of this review is on recent information dealing with the maturation of conifer somatic embryos.     

Conservation and diversity in flower land

During the past decade, enormous progress has been made in understanding the molecular regulation of flower development. In particular, homeotic genes that determine the identity of the floral organs have been characterised from different flowering plants, revealing considerable conservation among angiosperm species. On the other hand, evolutionary diversification has led to enormous variation in flower morphology. Increasing numbers of reports have described differences in the regulation, redundancy and function of homeotic genes from various species. These fundamentals of floral organ specification are therefore an ideal subject for comparative analyses of flower development, which will lead to a better understanding of plant evolution, plant development and the complexity of molecular mechanisms that control flower development and morphology.     

Analyzing female gametophyte development and function: There is more than one way to crack an egg

In flowering plants, gametes are formed in specialized haploid structures, termed gametophytes. The female gametophyte is a few-celled structure that integrates such diverse functions as pollen tube attraction, sperm cell release, gamete fusion and seed initiation. These processes are realized by distinct cell types, which ensure reproductive success in a coordinated manner. In the past decade, much progress has been made concerning the molecular nature of the functions carried out by the different cell types. Here, we review recent work that has shed light on female gametophyte development and function with a particular focus on approaches that have led to the isolation of genes involved in these processes.     

Ras and Phosphoinositide 3-Kinase: Partners in Development and Tumorigenesis

Much progress has been made in understanding the myriad of intracellular signalling pathways responsible for control of cell physiology. Signalling downstream of receptor tyrosine kinases (RTKs) is probably the most studied signalling mechanism to date and many of the molecular components and corresponding interactions involved have been delineated. Importantly, deregulation of RTK signalling has been implicated in the formation and maintenance of many human tumours. Two of the pivotal molecular components in RTK signalling, Ras and phosphoinositide 3-kinase (PI 3-kinase), have been shown to bind to each other, leading to the activation of PI 3-kinase. However, in addition to this Ras - PI 3-kinase interaction, first described over a decade ago, several other molecular interactions have more recently been described that appear to mediate the same signal. This has brought into question the physiological relevance of the Ras – PI 3-kinase interaction during RTK signalling. Through disruption of the interaction in a mouse model, we have now confirmed that the interaction is highly functional in vivo both during mammalian development and during Ras-induced tumorigenesis. Many questions still remain: in this Perspective, we explore the remaining uncertainties surrounding the role of this signalling mechanism, as well as the future directions that will likely shed further light on its role within cells.     

Cell-intrinsic regulators of proliferation in vertebrate retinal progenitors

The proliferative expansion of retinal progenitor cells (RPCs) is a fundamental mechanism of growth during vertebrate retinal development. Over the past couple of years, significant progress has been made in identifying genes expressed in RPCs that are essential for their proliferation, and the molecular mechanisms are beginning to be resolved. In this review, we highlight recent studies that have identified regulatory components of the RPC cell cycle machinery and implicate a set of homeobox genes as key regulators of proliferative expansion in the retina.     

The Angiosperm Gibberellin-GID1-DELLA Growth Regulatory Mechanism: How an “Inhibitor of an Inhibitor” Enables Flexible Response to Fluctuating Environments

The phytohormone gibberellin (GA) has long been known to regulate the growth, development, and life cycle progression of flowering plants. However, the molecular GA-GID1-DELLA mechanism that enables plants to respond to GA has only recently been discovered. In addition, studies published in the last few years have highlighted previously unsuspected roles for the GA-GID1-DELLA mechanism in regulating growth response to environmental variables. Here, we review these advances within a general plant biology context and speculate on the answers to some remaining questions. We also discuss the hypothesis that the GA-GID1-DELLA mechanism enables flowering plants to maintain transient growth arrest, giving them the flexibility to survive periods of adversity.     

Engineering virus resistance in agricultural crops

Plant viral genomes are relatively small and in the past decade many have been characterized at the molecular level. This has prompted research into the development of virus resistance based on interference with the viral multiplication cycle by the introduction of viral sequences into the plant genome. Several strategies have been tested. The most successful one so far involves the constitutive expression of the coat protein gene of the virus against which resistance is desired. In this review we describe progress made in engineering virus resistance into potato, an important agricultural crop. To this end the molecular structure of the potato viruses X and Y and leafroll is discussed as well as the introduction of resistance against potato virus X into potato. In addition, we address the question of preservation of cultivar-specific characteristics, an important prerequisite for commercial application. Finally, recent investigations for alternative forms of virus resistance are described against the background of the results of coat protein-mediated protection.     

Ambient temperature signaling in plants: An emerging field in the regulation of flowering time

Plants show remarkable developmental plasticity to survive in a continually changing environment. One example is their capability to adjust flowering time in response to environmental changes. Ambient growth temperature, which is strongly affected by global temperature changes, has a profound effect on flowering time. However, those effects have been largely ignored in research. Recent molecular genetic studies ofArabidopsis as a model system have implicated several genes, and have identified a molecular mechanism underlying the responses of plants to changes in ambient temperature. Here, we describe recent discoveries related to ambient temperature signaling and the control of flowering time inArabidopsis. We also discuss current perspectives on how plants sense and respond to such changes.     

兰花花发育的分子生物学研究进展

兰科植物是开花植物中最大的家族之一,其花高度进化,具有花瓣状的萼片,特化的唇瓣和雌雄蕊合生的蕊柱,是单子叶植物花发育生物学研究的理想材料。近年来有关兰花花发育基因调控的研究已取得了一些进展,本文从兰花开花转换和兰花花器官的形成两方面综述了近年来国内外关于兰花花发育分子机理方面的研究进展,主要介绍了文心兰、蝴蝶兰和石斛兰的花发育相关基因,并推测了兰花花被的进化发育过程,认为兰花的DEFICIENS(DEF)类基因在早期经过两轮复制,形成了四类DEF基因,从而促进了花萼与花瓣的分离、侧瓣与唇瓣的分离。该文最后对今后兰花花发育研究的发展方向进行了展望。     

模式植物拟南芥开花时间分子调控研究进展

植物从营养生长到生殖生长的转变是开花发育的关键,在合适的时间开花对植物的生长和繁衍极为重要,植物开花时间的调控对农业生产发展意义重大。植物开花是由遗传因子和环境因子协同调节的一个复杂过程。近年来,对不同植物开花调控的研究,特别是对模式植物拟南芥（Arabidopsis thaliana（L.） Heynh.）的开花调控研究取得了显著进展,已探明开花时间分子调控的6条主要途径分别是光周期途径、春化途径、自主途径、温度途径、赤霉素途径和年龄途径。各遗传调控途径既相互独立又相互联系,构成一个复杂的开花调控网络。本文综述了模式植物拟南芥开花时间调控分子机制相关研究的最新进展,并对未来的研究进行了展望。     

2008年中国植物科学若干领域重要研究进展

在国家各类重大研究计划的持续支持和推动下, 2008年中国植物科学研究继续快速发展, 中国科学家在植物科学各领域中取得了大量的原创性研究成果, 尤其是在水稻株型功能基因组、水稻开花控制和种子发育、生殖隔离机制以及转基因生态安全研究等方面取得了一系列重大进展, 受到了国内外的广泛关注。该文对2008年中国本土科学家在植物生命科学若干领域取得的重要研究进展进行概括性评述, 旨在全面追踪当前中国植物科学领域发展的最新前沿和热点事件, 并展现我国科学家所取得的杰出成就。     

Molecular mechanisms for the photoperiodic regulation of flowering in soybean

Photoperiodic flowering is one of the most important factors affecting regional adaptation and yield in soybean (Glycine max). Plant adaptation to long-day conditions at higher latitudes requires early flowering and a reduction or loss of photoperiod sensitivity; adaptation to short-day conditions at lower latitudes involves delayed flowering, which prolongs vegetative growth for maximum yield potential. Due to the influence of numerous major loci and quantitative trait loci (QTLs), soybean has broad adaptability across latitudes. Forward genetic approaches have uncovered the molecular basis for several of these major maturity genes and QTLs. Moreover, the molecular characterization of orthologs of Arabidopsis thaliana flowering genes has enriched our understanding of the photoperiodic flowering pathway in soybean. Building on early insights into the importance of the photoreceptor phytochrome A, several circadian clock components have been integrated into the genetic network controlling flowering in soybean: E1, a repressor of FLOWERING LOCUS T orthologs, plays a central role in this network. Here, we provide an overview of recent progress in elucidating photoperiodic flowering in soybean, how it contributes to our fundamental understanding of flowering time control, and how this information could be used for molecular design and breeding of high-yielding soybean cultivars.     

2008年中国植物科学若干领域重要研究进展

在国家各类重大研究计划的持续支持和推动下,2008年中国植物科学研究继续快速发展,中国科学家在植物科学各领域中取得了大量的原创性研究成果,尤其是在水稻株型功能基因组、水稻开花控制和种子发育、生殖隔离机制以及转基因生态安全研究等方面取得了一系列重大进展,受到了国内外的广泛关注。该文对2008年中国本土科学家在植物生命科学若干领域取得的重要研究进展进行概括性评述,旨在全面追踪当前中国植物科学领域发展的最新前沿和热点事件,并展现我国科学家所取得的杰出成就。