Long-distance stress and developmental signals associated with abscisic acid signaling in environmental responses

Flowering plants consist of highly differentiated organs, including roots, leaves, shoots and flowers, which have specific roles: root system for water and nutrient uptake, leaves for photosynthesis and gas exchange and reproductive organs for seed production. The communication between organs through the vascular system, by which water, nutrient and signaling molecules are transported, is essential for coordinated growth and development of the whole plant, particularly under adverse conditions. Here, we highlight recent progress in understanding how signaling pathways of plant hormones are associated with long-distance stress and developmental signals, with particular focus on environmental stress responses. In addition to the root-to-shoot peptide signal that induces abscisic acid accumulation in leaves under drought stress conditions, we summarize the diverse stress-responsive peptide signals reported to date to play a role in environmental responses.     

Gymnosperm Orthologues of Class B Floral Homeotic Genes and Their Impact on Understanding Flower Origin

Class B floral homeotic genes play a key role in specifying the identity of male reproductive organs (stamens) and petals during the development of flowers. Recently, close relatives (orthologues) of these genes have been found in diverse gymnosperms, the sister group of the flowering plants (angiosperms). The fact that such genes have not been found so far, despite considerable efforts, in mosses, ferns or algae, has been taken as evidence to suggest that B genes originated 300–400 million years ago in a lineage that led to extant seed plants. Gymnosperms do not develop petals, and their male reproductive organs deviate considerably from angiosperm stamens. So what is the function of gymnosperm B genes? Recent experiments revealed that B genes from diverse extant gymnosperms are exclusively expressed in male reproductive organs (microsporophylls). At least for some of these genes it has been shown that they can partially substitute for the Arabidopsis B genes AP3 and PI in ectopic expression experiments, or even partially substitute these genes in different class B floral organ identity gene mutants. This functional complementation, however, is restricted to male organ development. These findings strongly suggest that gymnosperm and angiosperm B genes have highly related interaction partners and equivalent functions in the male organs of their different host species. It seems likely that in extant gymnosperms B genes have a function in specifying male reproductive organs. This function was probably established already in the most recent common ancestor of extant gymnosperms and angiosperms (seed plants) 300 million years ago and thus represents the ancestral function of seed plant B genes, from which other functions (e.g., in specifying petal identity) might have been derived. This suggests that the B gene function is part of an ancestral sex determination system in which B gene expression specifies male reproductive organ development, while the absence of B gene expression leads to the formation of female reproductive organs. Such a simple switch mechanism suggests that B genes might have played a central role during the origin of flowers. In the out-of-male and out-of-female hypotheses changes in B gene expression led to the origin of hermaphroditic flower precursors out of male or female gymnosperm reproductive cones, respectively. We compare these hypotheses with other recent molecular hypotheses on the origin of flowers, in which C/D and FLORICAULA/LEAFY-like genes is given a more prominent role, and we suggest how these hypotheses might be tested in the future.     

Strong postmating reproductive isolation in Mimulus section Eunanus

Postmating reproductive isolation can help maintain species boundaries when premating barriers to reproduction are incomplete. The strength and identity of postmating reproductive barriers are highly variable among diverging species, leading to questions about their genetic basis and evolutionary drivers. These questions have been tackled in model systems but are less often addressed with broader phylogenetic resolution. In this study we analyse patterns of genetic divergence alongside direct measures of postmating reproductive barriers in an overlooked group of sympatric species within the model monkeyflower genus, Mimulus. Within this Mimulus brevipes species group, we find substantial divergence among species, including a cryptic genetic lineage. However, rampant gene discordance and ancient signals of introgression suggest a complex history of divergence. In addition, we find multiple strong postmating barriers, including postmating prezygotic isolation, hybrid seed inviability and hybrid male sterility. M. brevipes and M. fremontii have substantial but incomplete postmating isolation. For all other tested species pairs, we find essentially complete postmating isolation. Hybrid seed inviability appears linked to differences in seed size, providing a window into possible developmental mechanisms underlying this reproductive barrier. While geographic proximity and incomplete mating isolation may have allowed gene flow within this group in the distant past, strong postmating reproductive barriers today have likely played a key role in preventing ongoing introgression. By producing foundational information about reproductive isolation and genomic divergence in this understudied group, we add new diversity and phylogenetic resolution to our understanding of the mechanisms of plant speciation.     

ADAMTS proteases in fertility

The reproductive organs are unique among adult organs in that they must undergo continual tissue remodelling as a key aspect of their normal function. The processes for persistent maturation and release of new gametes, as well as fertilisation, implantation, placentation, gestation and parturition involve cyclic development and regression of tissues that must continually regenerate to support fertility. The ADAMTS family of proteases has been shown to contribute to many aspects of the tissue morphogenesis required for development and function of each of the reproductive organs. Dysregulation or functional changes in ADAMTS family proteases have been associated with reproductive disorders such as polycystic ovarian syndrome (PCOS) and premature ovarian failure (POF). Likewise, proteolytic substrates of ADAMTS enzymes have also been linked to reproductive function. New insight into the roles of ADAMTS proteases has yielded a deeper understanding of the molecular mechanisms behind fertility with clinical potential to generate therapeutic targets to resolve infertility, develop biomarkers that predict dysfunction of the reproductive organs and potentially offer targets for development of non-hormonal male and female contraceptives.     

桃儿七不同器官中营养成分分布状况及其生态学意义

植物生殖生态学是植物学领域中刚刚兴起并迅速发展的学科 ,近年来生活史进化理论的研究 ,使繁殖分配 (ｒｅｐｒｏｄｕｃｔｉｖｅａｌｌｏｃａｔｉｏｎ (ＲＡ ) )与繁殖投资(ｒｅｐｒｏｄｕｃｔｉｖｅｅｆｆｏｒｔ (ＲＥ) )研究成为植物生态学研究的主要焦点[7] 。目前在植物繁殖分配与繁殖投资研究中 ,通常用生物量作为衡量指标 ,这种方法遇到两个疑难问题 :一是各种成分在植物器官中的含量及比例各不相同 ,而且各种成分在植物生长发育过程中所起的生理功能也是不等价的 ,因此 ,在重量相同时 ,各器官的综合营养价值及生理功能是不等价的 ,生…     

Molecular control of autonomous embryo and endosperm development

Precocious seed development is usually prevented by a series of mechanisms that ensure seed production results from double fertilization. These events are circumvented in natural apomictic plant species that reproduce clonally through seed. Recent advances in molecular genetics using mutagenic approaches in model sexual plant species, such as Arabidopsis and Zea mays, have revealed some of the mechanisms that prevent such precocious seed development. An understanding of these mechanisms may lead to the development of techniques that will allow future crop plant species exhibiting hybrid vigor to be engineered such that their complex genomes can be fixed indefinitely, thereby maintaining high yields. Our current understanding of the mechanisms underlying the processes of reproductive development is discussed in this review.     

Embryological features of Alhagi persarum (Fabaceae): Adapt to environmental constraints

Reproductive organs, in flowering plants, are sensitive to stressful environments. Alhagi persarum Boiss. & Buhse copes with the stresses and produce reproductive organs under difficult climatic conditions. Embryological characters of this plant were investigated for the first time using different microscopy and staining techniques. The results of this study showed unique reproductive characters and strategies in A. persarum that we named reproductive adaptation. These characters have roles in protection and nutrition of reproductive organs, some of which were visible in ovule: accumulation of phenolic compounds, presence of ovular endothelium with its cuticle coat, hypostase, postament, endosperm haustorium, presence of operculum, curvature of the embryonic axis. The other characters in the seed are macrosclereid cells with cuticle coat, double palisade layer and lignified tracheids in hilar groove. Thickness increasing of endothecium and exine are the adaptive characters in anther. Unlike many of the stress-sensitive plants, all developmental stages of the embryo sac, anther, pollen and pollen tube are without any defects in these stress-tolerant plants. Seed germination rate is low in this species that is due to the hardness of seed coat which causes seed deep exogenous dormancy. This dormancy is also a developmental program for stress tolerance to keep seed viability for a long time in difficult conditions.     

Structure of floral galls of Byrsonima sericea (Malpighiaceae) induced by Bruggmanniella byrsonimae (Cecidomyiidae,Diptera) and their effects on host plants

Galls are anomalies in plant development from parasitic origin, and affect cellular differentiation or growth of plants. This parasite–plant interaction occurs in many environments and typically in vegetative organs of plants. The existence of galls in reproductive organs and their effects on the host plant are seldom described in the literature. In this paper, we present a novel study of galls in plants of the neotropical region. Galls of Bruggmmaniella byrsonimae develop in the flower buds of Byrsonima sericea DC. (Malpighiaceae) and affect development of the reproductive organs and the reproductive effort of these plants. The sepals and petals show hypertrophy of parenchyma tissues after differentiation, and the stamens exhibit degeneration of the sporogenic tissue. The gynoecium is not entirely developed; ovary and ovules are often absent. Changes in vascular tissues are also frequent, which may indicate high demand for nutrient resources by the new tissues initiated by the larva. We compared the amount of inflorescences, galls and fruits to evaluate possible effects on host reproduction. The results suggest that the Cecidomyiidae galls in flower organs affect fruit set and the reproductive success of B. sericea.     

Preferential localization of abscisic acid in primordial and nursing cells of reproductive organs of Arabidopsis and cucumber

Abscisic acid (ABA) is known to function in plant stress responses and seed dormancy, and much is known about its detailed mechanisms of signal transduction. Recent studies suggest that this hormone may also play important roles in sugar signaling and assimilate distribution during fruit development. However, little is known about the role of ABA in actively growing or differentiating fruits and other plant organs or tissues. To explore whether ABA functions during the early development of reproductive organs, we carried out ABA immunolocalization using monoclonal antibodies. The specific ABA accumulation pattern was verified by gas chromatography-mass spectrometry (GC-MS). ABA was not only detected in primordial cells of flower organs, but was also detected in nursing cells (e.g. tapetum and integuments), which function in supplying nutrition for germ cell development. These findings suggest that, in addition to its well-known function as a 'negative hormone', ABA may play some 'positive' roles during plant development, including possible involvement in the regulation of assimilate distribution.     

MADS-box genes active in developing pollen cones of Norway spruce (Picea abies) are homologous to the B-class floral homeotic genes in angiosperms.

The reproductive organs of conifers, the pollen cones and seed cones, differ in morphology from the angiosperm flower in several fundamental respects. In this report we present evidence to suggest that the two plant groups, in spite of these morphological differences and the long evolutionary distance between them, share important features in regulating the development of the reproductive organs. We present the cloning of three genes, DAL11, DAL12, and DAL13, from Norway spruce, all of which are related to the angiosperm B-class of homeotic genes. The B-class genes determine the identities of petals and stamens. They are members of a family of MADS-box genes, which also includes C-class genes that act to determine the identity of carpels and, in concert with B genes specify stamens in the angiosperm flower. Phylogenetic analyses and the presence of B-class specific C-terminal motifs in the DAL protein sequences imply homology to the B-class genes. Specific expression of all three genes in developing pollen cones suggests that the genes are involved in one aspect of B function, the regulation of development of the pollen-bearing organs. The different temporal and spatial expression patterns of the three DAL genes in the developing pollen cones indicate that the genes have attained at least in part distinct functions. The DAL11, DAL12, and 13 expression patterns in the pollen cone partly overlap with that of the previously identified DAL2 gene, which is structurally and functionally related to the angiosperm C-class genes. This result supports the hypothesis that an interaction between B- and C-type genes is required for male organ development in conifers like in the angiosperms. Taken together, our data suggests that central components in the regulatory mechanisms for reproductive organ development are conserved between conifers and angiosperms and, thus, among all seed plants.     

Axial nature of the cupule-bearing organ in Caytoniales

Caytoniales are an important group of seed plants, and the nature of their female reproductive organ may influence interpretations of the seed plant phylogeny and the origin of angiosperms. Although not convincingly demonstrated by clear evidence, cupules on previously described specimens were interpreted as being distichously arranged, implying that the cupule-bearing organ in Caytoniales was a pinnate megasporophyll. Here a female reproductive organ of Paracaytonia hongtaoi gen. et sp. nov. (Caytoniales) is reported from Liaoning, China. The well preserved specimen clearly shows a spiral arrangement of cupules along the reproductive axis, suggesting that the cupule-bearing organ in Caytoniales is not a megasporophyll but a branch. This new information on the axial nature of the cupule-bearing organ in Caytoniales has significant implications on the placement of Caytoniales in the seed plant phylogeny and interpretation of the relationship between Caytoniales and angiosperms.     

Phylogenetic and growth form variation in the scaling of nitrogen and phosphorus in the seed plants

Plant biomass and nutrient allocation explicitly links the evolved strategies of plant species to the material and energy cycles of ecosystems. Allocation of nitrogen (N) and phosphorus (P) is of particular interest because N and P play pivotal roles in many aspects of plant biology, and their availability frequently limits plant growth. Here we present a comparative scaling analysis of a global data compilation detailing the N and P contents of leaves, stems, roots, and reproductive structures of 1,287 species in 152 seed plant families. We find that P and N contents (as well as N : P) are generally highly correlated both within and across organs and that differences exist between woody and herbaceous taxa. Between plant organs, the quantitative form of the scaling relationship changes systematically, depending on whether the organs considered are primarily structural (i.e., stems, roots) or metabolically active (i.e., leaves, reproductive structures). While we find significant phylogenetic signals in the data, similar scaling relationships occur in independently evolving plant lineages, which implies that both the contingencies of evolutionary history and some degree of environmental convergence have led to a common set of rules that constrain the partitioning of nutrients among plant organs.     

植物离体器官发生控制机理研究进展

植物离体器官发生不仅是获得大量无性繁殖植物和进行基因转化的重要途径, 而且亦是研究植物发育问题的主要实验系统之一。迄今为止, 包括营养器官和生殖器官在内的几乎所有的器官都可以在离体条件下得到再生, 为深入研究植物离体器官发生的分子机理奠定了基础。本文着重介绍了营养器官发生过程基因表达的调节及重要功能基因的作用, 并对器官特征决定基因在生殖器官发生过程中的作用进行了分析, 提出了揭示离体器官发生分子机理的主要途径。     

植物离体器官发生控制机理研究进展

植物离体器官发生不仅是获得大量无性繁殖植物和进行基因转化的重要途径,而且亦是研究植物发育问题的主要实验系统之一。迄今为止,包括营养器官和生殖器官在内的几乎所有的器官都可以在离体条件下得到再生,为深入研究植物离体器官发生的分子机理奠定了基础。本文着重介绍了营养器官发生过程基因表达的调节及重要功能基因的作用,并对器官特征决定基因在生殖器官发生过程中的作用进行了分析,提出了揭示离体器官发生分子机理的主要途径。     

DELLA蛋白在被子植物有性生殖中的作用

DELLA蛋白是植物生长发育过程中响应赤霉素(GA)应答途径的关键调控因子, 主要行使转录调控因子的功能, 几乎参与了植物生长发育的各个重要过程。已有的研究表明, DELLA蛋白在被子植物的雄性生殖器官、雌性生殖器官和胚胎等组织中均有表达, 在植物有性生殖过程中起着极其重要的作用。该文综述了DELLA蛋白的分子结构、特性及其在植物有性生殖过程中的表达与功能, 并讨论了现存的问题及研究思路。     

Altering sexual development inArabidopsis

The reproductive system determines the way in which gametes develop and interact to form a new organism. Therefore, it exerts the primary level of control of genotypic frequencies in plant populations, and plays a fundamental role in plant breeding. A basic understanding of plant reproductive development will completely transform current breeding strategies used for seed production. Apomixis is an asexual form of reproduction in which embryogenesis occurs in a cell lineage lacking both meiosis and fertilization, and that culminates in the formation of viable progeny genetically identical to the mother plant. The transfer of apomixis into sexual crops will allow the production of self-perpetuating improved hybrids, and the fixation of any desired heterozygous genotype. The initiation of apomictic development invariably takes place at early stages of ovule ontogeny, before the establishment of the megagametophytic phase. The developmental versatility associated with megagametophyte formation suggests that the genetic and molecular regulation of apomixis is intimately related to the regulation of sexuality. Differences between the initiation of sexual and apomictic development may be determined by regulatory genes that act during megasporogenesis, and that control events leading to the formation of unreduced female gametophytes. To test this hypothesis, we are isolating and characterizing genes that act during megasporogenesis inArabidopsis thaliana and investigating their potential role in the induction of apomixis. We are using a recently established transposon-based enhancer detection and gene trap insertional mutagenesis system that allows the identification of genes based on their expression patterns. An initial screen of transposants has yielded over 20 lines conferring restricted GUS expression during early ovule development. We have obtained the sequence of genomic fragments flanking the transposon insertion. Several have homology to genes playing important roles in plant and animal development. They include cell cycle regulators, enzymes involved in callose hydrolysis, leucine-rich repeat protein kinase receptors, and expressed sequence tags (ESTs) of unknown function. Independently, a genetic screen allows the identification of female sterile mutants defective in megasporogenesis. Results from these experiments will improve our basic understanding of reproductive development in plants, and will set the basis for a sustained effort in plant germ line biotechnology, a first step toward a flexible transfer of apomixis into a large variety of sexual crops.     

AGAMOUS subfamily MADS-box genes and the evolution of seed cone morphology in Cupressaceae and Taxodiaceae

In this comparative developmental genetics study, we test hypotheses based on fossil and morphological data on reproductive organ morphology and evolution in conifers--specifically, the ovule-bearing organ in Cupressaceae and Taxodiaceae. Genes homologous to the Arabidopsis gene AGAMOUS are expressed in ovuliferous scales of spruces (Picea) throughout development. Previous studies have shown that the AGAMOUS subfamily of MADS-box genes predates the split between angiosperms and gymnosperms, and that these genes have in part conserved functions in reproductive development among seed plants, especially in the specification of identity of the ovule-bearing organs. These data indicate that their expression in conifer families other than Pinaceae might be used as markers for organs homologous to the Pinaceae ovuliferous scale. Here we have isolated putative AGAMOUS orthologs from Cupressaceae and Taxodiaceae and analyzed their expression pattern in seed cones to test for the presence of morphological homologs of ovuliferous scales. Our results were not congruent with the hypothesis that the tooth of the Cryptomeria seed cone is homologous to the Picea ovuliferous scale. Likewise, the hypothesis that the bracts of Thujopsis and Juniperus contain fused ovuliferous scales was not supported. However, we found expression of AGAMOUS homologs in the sterile bracts of Cupressaceae seed cones at late developmental stages. This expression probably represents a novel gene function in these conifer families, since no corresponding expression has been identified in Pinaceae. Our study suggests that the evolutionary history of modern conifer cones is more diverse than previously thought.     

细叶百合的生物量和营养分配

 以栽培的2年生细叶百合（Lilium pumilum）为材料,于2000年的生长季从蕾期至种子成熟期进行6次取样,对其各器官生物量和氮、磷元素的配置进行了动态研究。结果表明,细叶百合虽然以种子繁殖为主,但在整个生长季用于生殖器官的生物量投资的比例并不很大,大量干物质分配到地下器官鳞茎中（平均为60.17%）;茎、叶的生物量分配比例仅次于鳞茎;雄蕊生物量分配比例明显高于雌蕊。在叶萌动及展叶初期植株全氮百分含量最高;从春季萌动至秋季果实成熟,叶中的氮呈逐渐递减的趋势;茎和生殖器官的全氮含量在蕾期最大;生殖器官与叶、鳞茎的全氮含量相关显著。磷在生殖器官的含量较高,这与磷在植物有性生殖过程中的重要作用相一致;生殖器官与茎的全磷含量相关显著。地下器官全氮、全磷随季节变化有增多的趋势;地上各器官全氮、全磷相关显著,随季节变化有明显减少的趋势。