Sexual Plant Reproduction: a Fertile and Flourishing Field

Since the very beginning of plant science, sexual plant reproduction (SPR) has proved an attractive and enduring topic for generations of botanists. With the rapid development of modern technology, a significant acceleration has occurred in our understanding on the developmental mechanisms of plant reproductive processes, particularly the evolution of double fertilisation, signalling in pollen tube orientation, molecular characterisation of plant gametes, maternal to zygotic transitions and parental gene involvement in early embryogenesis. This is reflected not only by several recent high-ranking research papers, but also by the frequent conferences and workshops on these topics. These include the 2008 XXth International Congress on SPR in Bras´齦ia and “Frontiers in SPR III” in Tucson, as well as “Cell-Cell Communication in Plant Reproduction” held in 2009 in Bath. The continuing efforts from around the world indicate that SPR is still a fertile and flourishing field, with great expectations for the coming decade. Investigations on SPR have been enhanced recently by their underlying relationship to agriculture. With the development of molecular crop breeding comes an increasing requirement for knowledge on molecular mechanisms of SPR, both general regulatory processes, and in particular, signalling for cell-cell communication in several critical steps. To reveal mechanisms behind some well-known phenomena in modern agriculture, such as compatibility of crop crosses and fertility determination of remote hybrids and heterosis, one must first precisely understand the basic developmental processes and molecular mechanisms involved in SPR. Thus, it is not surprising that the field has attracted much attention in recent years. In fact, advances in the study of SPR throw new light on investigations for solving many existing problems in agriculture. This special issue presents current research on multiple aspects of SPR, both pre- and post-fertilisation. Hence, this special issue of the Journal of Integrative Plant Biology features a diverse collection of papers. One paper, “The earliest normal flower in Liaoning Province, China” (see pages 800–811), presents evidence of component parts and morphology of early angiosperm flowers. Four papers, “A genome-wide functional characterisation of Arabidopsis regulatory calcium sensors in pollen tubes” (see pages 751–761), “GNOM-LIKE 2, encoding an ARF-GEF protein homologous to GNOM and GNL1, is essential for pollen germination in Arabidopsis” (see pages 762–773), “Regulation of actin dynamics in the pollen tubes:control of actin polymer level” (see pages 740–750) and “Pollen tube growth: a delicate equilibrium between secretory and endocytic pathways” (see pages 727–739), deal with molecular mechanisms of pollen tube growth and orientation, a hot field in SPR. Amongst these papers, Prof. Moscatelli offers a deep insight into dynamic control of vesicle trafficking in pollen tubes. In the signalling cascade of vesicle trafficking, calcium and actin dynamics play essential roles in the balance between secretory and endocytic pathways. GNOM-LIKE 2, as an ARF-GEF- and BFA-sensitive protein,may indirectly influence calcium and actin dynamics during pollen germination and pollen tube growth. “Premature tapetum degeneration: a major cause of abortive pollen development in photoperiod sensitive genic male sterility in rice” (see pages 774–781) presents new evidence for the interaction between tapetum and pollen development. “Comparative detection of calcium fluctuations in single female sexual cells of tobacco to distinguish calcium signals triggered by in vitro fertilisation” (see pages 782–791) reports observations on calcium dynamics during sperm-central cell fusion, and “Oil body biogenesis during Brassica napus embryogenesis” (see pages 792–799) focuses on post-fertilisation developmental events, mainly on oil body generation and accumulation during embryogenesis in both wild type and mutants. A review paper, “Analyses of sexual reproductive success in transgenic and/or mutant plants” (see pages 719–726), gives a critical evaluation of current techniques used for investigating genes that affect pistil development, and provides useful information and technical guidance to readers in this field. These papers coherently address the common theme: development and its mechanisms in plant reproductive processes. In this way, we hope to create an atmosphere in which extensive discussion can stimulate and lead to interactions between scientists with different perspectives in order to inspire future directions. We sincerely hope that this special issue of JIPB will provide a platform to highlight current advances and novel findings in the study of SPR. Finally, we express our appreciation to JIPB for supporting this special issue and to all authors for their great contributions. Mengxiang Sun, Professor The Editor for this Special Issue College of Life Sciences, Wuhan University, China     

Origins of Eukaryotic Sexual Reproduction

Sexual reproduction is a nearly universal feature of eukaryotic organisms. Given its ubiquity and shared core features, sex is thought to have arisen once in the last common ancestor to all eukaryotes. Using the perspectives of molecular genetics and cell biology, we consider documented and hypothetical scenarios for the instantiation and evolution of meiosis, fertilization, sex determination, uniparental inheritance of organelle genomes, and speciation.The transition from prokaryote to protoeukaryote to the last eukaryotic common ancestor (LECA) entailed conservation, modification, and reconfiguration of preexisting genetic circuits via mutation, horizontal gene transfer (HGT), endosymbiosis, and selection, as detailed in previous articles of this collection. During the course of this evolutionary trajectory, the LECA became sexual, reassorting and recombining chromosomes in a process that entails regulated fusions of haploid gametes and diploid → haploid reductions via meiosis. That the LECA was sexual is no longer a matter of speculation/debate as evidence of sex, and of genes exclusively involved in meiosis, has been found in all of the major eukaryotic radiations (Brawley and Johnson 1992; Ramesh et al. 2005; Kobiyama et al. 2007; Malik et al. 2008; Phadke and Zufall 2009; Fritz-Laylin et al. 2010; Lahr et al. 2011; Peacock et al. 2011; Vanstechelman et al. 2013).We propose that the transition to a sexual LECA entailed four innovations: (1) alternation of ploidy via cell–cell fusion and meiosis; (2) mating-type regulation of cell–cell fusion via differentiation of complementary haploid gametes (isogametic and then anisogametic), a prelude to species-isolation mechanisms; (3) mating-type-regulated coupling of the diploid/meiotic state to the formation of adaptive diploid resting spores; and (4) mating-type-regulated transmission of organelle genomes. Our working assumption is that the protoeukaryote → LECA era featured numerous sexual experiments, most of which failed but some of which were incorporated, integrated, and modified. Therefore, this list is not intended to suggest a sequence of events; rather, the four innovations most likely coevolved in a parallel and disjointed fashion.Once these core sexual-cycle themes were in place, the evolution of eukaryotic sex has featured countless prezygotic and postzygotic variations, the outcome being the segregation of panmictic populations into distinct species with distinctive adaptations.For additional reviews on the evolution of sex, the interested reader is referred to Goodenough (1985), Dacks and Roger (1999), Schurko et al. (2009), Wilkins and Holliday (2009), Gross and Bhattacharya (2010), Lee et al. (2010), Perrin (2012), and Calo et al. (2013).     

Hormonal Control of Sexual Differentiation and Reproduction in Crustacea

SYNOPSIS. Sexual differentiation in malacostracan Crustaceais controlled by the androgenic gland hormone (AGH). In males,the primordial androgenic glands (AG) develop and AGH inducesmale morphogenesis. In females, the primordial AG does not developand the ovaries differentiate spontaneously. Implantation ofthe AG into females yields various results, showing that thesensitivity to AGH differs with the species and the receptiveorgans. Purified AGH of the isopod Armadillidium vulgare consistsof at least two molecular forms, which exist as monomeric proteinswith molecular weights of 17,000 ± 800 and 18,300 ±1,000 Da and with isoelectric points of about 4.5 and 4.3, respectively.The antiserum raised against purified AGH makes it possibleto measure AGH activity by immunoassay. Neurohormones control male and female reproduction. In males,they are involved in the maintenance of the male germinativezone and the control of AG activity. In females, the secondaryvitellogenesis is controlled by the vitellogenesis-inhibitinghormone (VIH) and the vitellogenesis- stimulating hormone (VSH).VIH isolated from the lobster Homarus americanus is a peptidewith a molecular weight of 9,135 Da and shows homology to thecrustacean hyperglycemic hormone and moltinhibiting hormone.Involvement of the molting hormone and the juvenile hormone-likecompound in the secondary vitellogenesis have also been suggested.In the amphipod Orchestia gammarella, the vitellogenesis- stimulatingovarian hormone (VSOH) seems to control vitellogenin synthesis     

Genetic Variation Underlying Sexual Behavior and Reproduction

Selection depletes additive genetic variation underlying traitsimportant in fitness. Intense mating competition and femalechoice may result in negligible heritability in males. Femalesoften appear to choose mates, however, suggesting genetic variationin males which is important to females. Evidence is reviewedon allelic substitutions, karyotypic variation, and especiallythe heritable variation of continuous traits involved in sexualbehavior and reproduction. Phenotypic variation in male matingspeed and courtship intensity, female mating and ovipositionbehavior, egg size and number, body size, parthenogenesis, andthe sex ratio generally have heritable variation. The maintenanceof genetic variation, and the meaning of heritability estimatesfor natural populations is considered.     

鲁中山区东亚三角头涡虫有性生殖过程研究初报

于2005年3-5月、9～11月对生活于鲁中山区的东亚三角头涡虫（Dugesia japonica）的有性生殖过程进行了研究,发现鲁中山区东亚三角头涡虫1年只有1次有性生殖过程。卵囊产出的高峰在4月,卵囊孵化与种群密度最高峰在5月,其有性生殖过程与温度、食物、虫体大小密切相关。经实验观察1个卵囊最多能孵出涡虫幼体10条,最少3条。     

有性生殖与食者—被食者体系中的极限环

1　引　言种群生物学的原始假设认为,在一定条件下,任一种群,不管是有性生殖种群还是无性生殖种群,其自然增长都遵守ＶｅｒｈｕｌｓｔＰｅａｒｌＬｏｇｉｓｔｉｃ方程。按照这一方程,种群有一个平衡点Ｓ,Ｓ=Ｋ,Ｋ是环境负荷容量;并且随着种群大小(或密度)Ｎ的增加,种群的个体(或相对)自然增长率ｄＮ/Ｎｄｔ单调下降。这是由于存在拥挤效应。Ｌｏｇｉｓｔｉｃ方程不含Ａｌｌｅｅ效应或过疏效应[1,2]。实际情况与Ｌｏｇｉｓｔｉｃ方程有所不同,由于存在“拥挤效应”和“过疏效应”,第一,有一个最适种群大小Ｎｍ:随着Ｎ增加,ｄＮ/Ｎｄｔ在Ｎ<Ｎ…     

Sexual and Asexual Reproduction in Natural Stands of Populus nigra

The balance between sexual and asexual propagation in the establishment of natural stands of Populus nigra was assessed from the genotypes of trees sampled in different natural stands. One site was completely sampled and genotyping proceeded using STS and RAPD markers. Among 118 trees, only four were vegetative copies of other trees of the site. Isozymes were used in four stands, and a method to detect the presence of vegetative copies in a sample is proposed for these markers. No vegetative copies were found in two cases, and a low number of copies was detected in the other two. Observations are reported for seedlings as well as for different modes of vegetative propagation in natural stands. We conclude that sexual and asexual propagation play complementary roles in the dynamics of this species, and that in most cases the adults originate from seedlings.     

被子植物有性生殖过程中的细胞程序死亡

细胞程序死亡是植物发育过程中的一种普遍现象。早就认识到高等植物生殖器官中一些细胞的死亡对植物有性生殖具有重要作用。这些细胞的死亡过程与动物组织中的细胞程序死亡基本相同。但植物体内诱导生殖细胞程序死亡的信号及其传导系统则显示出其特点 ,有些还表现出雌、雄性细胞的相互作用。探索植物生殖过程中的细胞程序死亡现象将有利于澄清植物生殖过程中的一些机理问题 ,使过去的细胞学研究结果深入到分子水平进行探讨     

阿拉伯半乳糖蛋白在被子植物有性生殖中的作用

阿拉伯半乳糖蛋白(arabinogalactan-proteins,AGPs)是一类主要分布在细胞表面和胞外基质中的糖蛋白.它们在植物的雄性器官(花粉、花粉管、精细胞)、雌性器官(柱头、花柱、子房)和胚胎(合子胚和体细胞胚)等组织和细胞中均有大量的表达.大量研究表明AGPs在被子植物有性生殖过程中起着非常重要的作用,既可能参与花粉管粘附、营养、传导或提供信号的作用,也可能参与受精过程中配子识别和受精后胚胎的发育与分化等过程.该文就其分子结构、特性以及在植物有性生殖过程中各种器官和组织内的表达和功能研究进展做了较为全面的概述.     

阳春砂有性生殖特性的研究进展(综述)

阳春砂是我国珍稀濒危的药用植物,以其果实入药。由于阳春砂柱头高于花药,自然传粉结实率低,严重制约了果实产量。为揭示阳春砂果实形成的基础,探讨提高阳春砂产量的对应策略,本文就阳春砂的形态特征、生态习性、花粉发育、胚囊发育及开花、传粉、受精等有性生殖研究状况进行综述。     

Sexual Dichromatism and Temporary Color Changes in the Reproduction of Fishes

SYNOPSIS. Studies on color patterns of fishes have focused onrelationships between bright, relatively permanent colors, suchas those of fishes inhabiting coral reef and tropical freshwaterhabitats, and ecological factors, such as competitors, predators,and the visual background. By comparison, the functions of,and hence the selective pressures acting on, temporary changesin nuptial coloration have received much less attention. Temporarycolor changes associated with reproduction occur in many freshwaterand marine groups. Nuptial coloration in fishes functions bothin agonistic interactions among males and courtship of females,so that it is subject to both intrasexual and intersexual selectionas well as natural selection. Temporal variation in nuptialcolor patterns is sensitive to temporal changes in the male'sphysical condition, motivation, and social status. Physiologicalprocesses, such as neuronal and endocrine changes, play importantroles in the expression of breeding colors, including rapidresponses to changes in social conditions. The importance ofproximal mechanisms and ultimate selective processes in mediatingrapid changes in the blue, melanin—based breeding colorsof pupfish, and the red, carotenoid—based color patternsin guppies are discussed in the context of signal function andevolution.     

Estimation of Blood Loss in a Small Community Hospital

Three methods of blood loss estimation which are simple, accurate and cheap are: (1) weighing of sponges; (2) estimation of blood volume with Evans blue dye and (3) measurement of central venous pressure (CVP).Weighing of sponges is a valuable operating-room procedure although it has certain defects some of which are described. The Evans dye method is used chiefly in preoperative assessment when hypovolemia is suspected but serial estimations are feasible and can be performed in 45 minutes. Measurement of CVP, however, is the best single criterion of effective blood volume in relation to cardiac functional capacity and is the best guide to blood and fluid requirements. A simple “homemade” device for making serial CVP determinations, incorporating a manometer and a zero level, is described.These methods of blood loss estimation do not supersede the traditional methods of the clinical assessment of the surgical patient, but are valuable adjuncts to such assessment.