绣球茜的二型花柱及其传粉生物学初步研究

首次对绣球茜(Dunnia sinensis Tutch)的花药和柱头高度、花粉和柱头形态,以及人工辅助授粉的结实情况等进行了研究.结果表明:绣球茜在同一居群中同时具有长花柱(Pin 型)和短花柱(Thrum)两种花型,长花柱植株的柱头和雄蕊高分别为9.61±0.36 mm和6.79±0.38 mm,短花柱则为6.11±0.56 mm和8.96±0.59 mm,表现出互补式雌雄异位的花部特征.通过人工辅助授粉,两种花型植株的自交和同型植株间异交都不结实,仅在型间异交方能正常结实,说明绣球茜中存在极强的自交不亲和和型内不亲和现象.在花粉与柱头形态方面:长柱型花的单花花粉量(38555.6±6258.4)显著地小于短柱型花(52145.45±8924.5)(t=4.009,P＜0.01),长柱花和短柱型花的胚珠数分别为38.73±1.85和39.1±2.25(t=-4.13,P＞0.01);长柱型花花粉粒的大小(极径21.27±0.70 μm)显著地小于短柱花(21.92±0.79μm)类型(t=3.890,P＜0.01),而柱头乳突大小长柱类型要大于短柱类型,表现出明显的二型性.研究结果表明绣球茜是一种典型的二型花柱植物.此外,对其传粉昆虫及昆虫访花行为的观察表明,蝶类(青风蝶属Graphium)和蜂类(熊蜂Bombus sp.和木蜂Xylocopa magnifica Smith)为绣球茜的主要访花昆虫和传粉昆虫,它们能够在两种不同花型植株之间有效地传粉.     

沙田柚自交不亲和花柱糖蛋白产生的时空关系

用辣根过氧化物酶标 Con A电镜细胞化学方法研究沙田柚不同发育时期的花柱通道细胞中糖蛋白的合成 ,分布和运输途径的动态变化。四分体期至开花期 ,在沙田柚花柱通道细胞中 ,内质网 (ER)合成糖蛋白呈颗粒状定位于核膜腔 ,内质网膜腔 ,质膜与细胞壁之间电子透明层中。授粉后 1～ 3d,内质网结构形态改变 ,由完整圆形变为开放 ,并囊泡化 ,大量线粒体集中于囊泡区 ,形成类似于哺乳动物腺外分泌细胞的高尔基区 ,内质网合成的糖蛋白在高尔基区膜囊中经糖基转移酶作用进一步浓缩凝结 ,形成与识别有关的糖蛋白 ,经高尔基小泡运送至通道细胞外壁。讨论了定位于通道细胞外壁的糖蛋白在沙田柚配子体型不亲和识别中的作用及与识别部位的关系。     

蓝花丹的花部形态二态性及自交不亲和特性

花部形态的二态性在异型自交不亲和中的作用一直颇具争议。为了探讨其对自交不亲和的作用,选择代表植物蓝花丹,观测其花部形态,利用激素调控其花柱高度,对调控后的花柱授粉,并分析结实率的变化。结果表明：(1)蓝花丹的花部形态在众多方面存在二态性;(2)IAA,NAA,GA 在适宜的浓度都能调节其花柱的长度;(3)调节后的花柱自然和人工授粉,结实率与空白对照相比无显著差异。实验结果说明蓝花丹的花部形态有着典型的二态性特征,此特征是蓝花丹对花型间互补式雌雄异位的进化适应策略;而雌雄性器官的空间分布并没有通过影响合法花粉的有效传播而影响自交不亲和性;异型花的自交不亲和性更多地还是体现在生理机制上。     

沙田柚配子体自交不亲和花柱消减文库的构建及分析

分别以沙田柚自交花柱cDNA为tester,异交花柱cDNA为driver,利用抑制性消减杂交技术构建了消减文库,文库的重组率高于95%,插入片段集中在100～500 bp之间,对文库部分克隆进行测序并与GenBank中的同源序列进行比较,发现了一些类似于SI、S9-RNase、激酶类等与自交不亲和相关的基因.     

被子植物异型花柱及其进化意义

异型花柱(heterostyly)是被子植物中一种特殊的花多态现象和雌雄异位形式,包括二型花柱(distyly)和三型花柱(tristyly)2种类型.据报道,在被子植物的约31个科中有异型花柱植物.该类型植物的花部特征在避免自交、促进准确的异交传粉以及通过降低雌雄功能干扰以提高亲本适合度等方面具有重要的进化意义.该文从以下3个方面总结和分析了异型花柱及其进化意义:(1)异型花柱植物的类型和花部特征、附属多态性和种群结构:(2)异型花柱植物在被子植物中的分布、起源和演化:(3)异型花柱植物的进化适应意义.结合目前作者开展的有关工作,对异型花柱植物研究中存在的一些问题进行讨论和展望,希望能为国内工作者开展该领域的研究提供一些参考.     

被子植物异型花柱及其进化意义

异型花柱(heterostyly)是被子植物中一种特殊的花多态现象和雌雄异位形式, 包括二型花柱(distyly)和三型花柱(tristyly) 2种类型。据报道, 在被子植物的约31个科中有异型花柱植物。该类型植物的花部特征在避免自交、促进准确的异交传粉以及通过降低雌雄功能干扰以提高亲本适合度等方面具有重要的进化意义。该文从以下3个方面总结和分析了异型花柱及其进化意义: (1)异型花柱植物的类型和花部特征、附属多态性和种群结构; (2)异型花柱植物在被子植物中的分布、起源和演化; (3) 异型花柱植物的进化适应意义。结合目前作者开展的有关工作, 对异型花柱植物研究中存在的一些问题进行讨论和展望, 希望能为国内工作者开展该领域的研究提供一些参考。     

芸薹属中自交不亲和反应的信号转导

自交不亲和现象在芸薹属(Brassica)植物中普遍存在,芸薹属中表现的是典型的孢子体型自交不亲和性.单元特异性的S位点受体激酶(SRK)基因和S位点花粉胞被蛋白(SCR/SP11)发生识别后,一系列相关蛋白-臂重复蛋白(ARC1)、M位点蛋白激酶(MLPK)等,引发了自交不亲和反应信号的传导,最终产生自交不亲和反应.文章就这方面的研究进展作介绍.     

配子体自交不亲和植物花粉S基因研究进展

配子体自交不亲和植物的自交不亲和性是由雌蕊自交不亲和因子和花粉自交不亲和因子相互作用的结果。目前已经分离和鉴定了雌蕊自交不亲和基因及其表达产物。最近从金鱼草、Prumusdulcis、梅等植物中分离的F-box基因,它具有花粉S基因特点,即在花药、成熟的花粉和花粉管中特异表达;在基因位置上,与S-RNase基因紧密连锁;不同物种或同一物种不同品种F-box基因间核苷酸和氨基酸序列上存在高度多态性。通过分子生物学方法和杂交授粉试验证明所分离的F-box基因是花粉自交不亲和基因,但目前尚未分离出该类基因相应的表达蛋白。主要综述了配子体自交不亲和植物花粉自交不亲和基因的发现、基因的结构、雌蕊自交不亲和因子和花粉自交不亲和因子相互作用的模型。     

二型花柱植物金荞麦的繁殖生态学研究

通过野外实验观察和人工控制套袋等方法,从金养麦的花部基本特征、开花动态、花粉胚珠比(P/O)、花粉活力、柱头可授性、杂交指数、套袋实验及访花昆虫等方面对其繁殖生态学进行了研究.结果显示:(1)金荞麦在同一居群中同时具有长柱型(L-型)和短柱型(S-型)两种花型,短花柱花直径(7.25±0.11 mm)显著大于长花柱花直径(6.79±0.11 mm),长花柱花的柱头和花药高分别为3.39±0.04 mm和1.80±0.02 mm,短花柱花的柱头和花药高则分别为1.89±0.04 mm和3.19±0.06 rnm,表现出互补式雌雄异位的花部特征.(2)金荞麦8～10月开花,单花序的花期为15～23 d,单花的花期为1～3 d,开花进程中,内轮雄蕊先散粉,外轮雄蕊后散粉;S-型花的花粉活力高于L型花的花粉活力,但其单花花粉量低于L-型花,显示了两种花型的自我调控机制.(3)套袋实验表明,金荞麦自花自交不亲和,但具有型内和型间亲和性,L型和S-型花的P/O值分别为810±40.48和526.5±42.24,表明其繁育系统为兼性异交,需要传粉者,但L-型花更倾向异交.(4)金荞麦的主要访花昆虫为膜翅目(Hymenoptera)、双翅目(Diptera)、鳞翅目(Lepidoptera)、半翅目(Hemiptera)和蜻蜒目(Odonata) 19个科37种昆虫,其中,两种花型拥有12种共同的访花昆虫,L-型花访花昆虫14种,S-型花访花昆虫35种,表明S-型花对昆虫具有更强的吸引力.研究表明,金荞麦是典型的二型花柱植物,虽然具有严格的自交不亲和性,但显示一定的型内亲和性.     

植物自交不亲和分子机理研究的一些进展

综述了植物孢子体自交不亲和（ＳＳＩ）与配子体不亲和（ＧＳＩ）分子机理研究的一些进展。ＳＬＧ和ＳＲＫ基因编码的ＳＬＧ和ＳＲＫ蛋白在ＳＳＩ中起着关键作用,而Ｓ基因编码的Ｓ蛋白（ＲＮａｓｅ）在ＧＳＩ中起着重要作用。禾本科植物的ＧＳＩ是受双位点Ｓ和Ｚ基因控制的,文中也作了简要介绍。     

Distyly and variation in heteromorphic incompatibility in Gaertnera vaginata (Rubiaceae) endemic to La Reunion Island

Documenting the floral biology of species throughout the Rubiaceae family is of particular interest since heterostyly and dioecy may have evolved more than once in this large family. Unfortunately many species in several tropical regions remain unstudied. The purpose of this paper is to describe the floral biology, the nature of self-incompatibility, morph ratios, and fecundity in natural populations of Gaertnera vaginata, a small tree endemic to the island of La Reunion in the Indian Ocean. Measurements of floral characters in populations across the entire distribution of this species showed that G. vaginata exhibits a reciprocal stigma height and anther height dimorphism characteristic of a distylous species. Pollen grain size and corolla tube length are consistently greater in short-styled plants and long-styled plants produce more pollen per flower. Controlled pollinations in a natural population showed that 25% of the short-styled plants gave at least one fruit on intramorph (illegitimate) pollination, whereas no long-styled plants set fruit on illegitimate pollination. In total, 19.4% of illegitimate pollinations produced fruit on short-styled plants. No self-pollination gave fruit on either morph and between-morph pollinations produced 92.2 and 92.8% for short and long-styled plants, respectively. Overall, short-styled plants were significantly more abundant than long-styled plants. Short-styled plants outnumbered long-styled plants in 16 of the 19 populations. In three of these populations the morph ratio was significantly different from 1:1. In two natural populations, fruit set was significantly higher on long-styled plants, although the number of seeds per fruit was not significantly different between the two morphs. The possible effect of variation in the strength of heteromorphic incompatibility on observed variation in morph abundance and the possible causes for the variation in fruit set are discussed.     

Distyly and sequential pollinators of Psychotria nuda (Rubiaceae) in the Atlantic rain forest, Brazil

Reciprocal herkogamy is known to promote intermorph-pollination in distylous species, which are generally self- and intramorph-incompatible. Legitimate crossing rates are also influenced by pollinator foraging strategy, which determines most of the pollen flow in natural populations. This study reports on the floral morphology, compatibility relations and pollination biology of Psychotria nuda (Cham. and Schltdl.) Wawra in the Atlantic rain forest, southeastern Brazil, based on floral measurements, hand-pollination experiments and focal observation of floral visitors. It was found that P. nuda does not present an exactly reciprocal herkogamy, however, this morphological trait in P. nuda is as good as in most of Rubiaceae. Reproductive experiments showed compatibility relations similar to those frequently observed in distylous species. The hummingbirds Ramphodon naevius and females of Thalurania glaucopis were the main pollinators of P. nuda, presenting the traplining foraging strategy, which seems to maximize intermorph crosses in P. nuda flowers. These hummingbirds pollinated P. nuda flowers sequentially throughout the flowering period.     

Distyly and heteromorphic incompatibility in oceanic island species ofErythroxylum (Erythroxylaceae)

Surveys of oceanic island floras have shown that heterostyly is usually absent in such regions, probably because this floral polymorphism is often associated with a self-incompatibility system. In this context we describe the floral biology of three species ofErythroxylum on La Réunion island and examine the compatibility relationships of one of these species,E. laurifolium. All three species are distylous but differ in relative stigma-anther separation in the different morphs. In general, short-styled flowers have greater stigma-anther separation than long-styled flowers, which are often homostylous in appearance. This lack of stigma-anther separation in long-styled flowers is due to style twisting which improves reciprocity at the high organ level. The reduced stigma-anther separation does not appear to be associated with the evolution of selfing asErythroxylum laurifolium shows heteromorphic self-incompatibility. The presence of heteromorphic incompatibility in a group of species that have colonized an oceanic island is discussed.     

Application of DNA barcodes in Hedyotis L.(Spermacoceae, Rubiaceae)

The potential application of DNA barcodes of plastid (matK, trnH-psbA, petD, and rbcL) and nuclear (internal transcribed spacer (ITS) of rDNA) DNA regions was investigated for 25 Hedyotis taxa. The ITS showed the best species discrimination by resolving 23 of the species as exclusive lineages with no shared alleles between any of the 24 distinct species (H. Assimilis and H. Mellii are not supported as distinct species based on our molecular and morphological data). Conversely, rbcL performed the worst and only resolved 10 of the species as exclusive lineages, and 10 species with shared alleles. Using ITS has the advantage of high PCR amplification success and it provides good intra- and interspecific variation distribution patterns. The most powerful plastid markers were petD and trnH-psbA, but we could amplify and sequence trnH-psbA for only 83% of the accessions sampled. Combination of ITS and petD performed extremely well, with all 24 of the distinct species resolved as exclusive lineages and no shared alleles between any of the distinct species. We therefore recommend ITS, or a combination of ITS and petD, as the standard DNA barcode in Hedyotis, but acknowledge that there are no shared alleles between distinct species for marK and rbcL combined.     

Cryptic self‐incompatibility and distyly in Hedyotis acutangula Champ. (Rubiaceae)

Distyly, floral polymorphism frequently associated with reciprocal herkogamy, self‐ and intramorph incompatibility and secondary dimorphism, constitutes an important sexual system in the Rubiaceae. Here we report an unusual kind of distyly associated with self‐ and/or intramorph compatibility in a perennial herb, Hedyotis acutangula. Floral morphology, ancillary dimorphisms and compatibility of the two morphs were studied. H. acutangula did not exhibit precise reciprocal herkogamy, but this did not affect the equality of floral morphs in the population, as usually found in distylous plants. Both pin and thrum pollen retained relatively high viability for 8 h. The pollen to ovule ratio was 72.5 in pin flowers and 54.4 in thrum flowers. Pistils of pin flowers remained receptive for longer than those of thrum flowers. No apparent difference in the germination rate of pin and thrum pollen grains was observed when cultured in vitro, although growth of thrum pollen tubes was much faster than that of pin pollen tubes. Artificial pollination revealed that pollen tube growth in legitimate intermorph crosses was faster than in either intramorph crosses or self‐pollination, suggesting the occurrence of cryptic self‐incompatibility in this species. Cryptic self‐incompatibility functioned differently in the two morphs, with pollen tube growth rates after legitimate and illegitimate pollination much more highly differentiated in pin flowers than in thrum flowers. No fruit was produced in emasculated netted flowers, suggesting the absence of apomixis. Our results indicate that H. acutangula is distylous, with a cryptic self‐incompatibility breeding system.     

Dioecy derived from distyly and pollination in Psychotria rubra (Rubiaceae) occurring in the Ryukyu Islands,Japan

Floral morphology and breeding system were examined in natural populations of Psychotria rubra (Rubiaceae) occurring in the Ryukyu Islands in southwest Japan. This species is morphologically dimorphic with long‐ and short‐styled morphs; however, these morphs are functionally dioecious. All long‐styled morphs set fruits, but their short anthers completely lack pollen grains; thus, they function as pistillate flowers. Alternately, short‐styled morphs usually have fertile pollen and never set fruit, whether after open or obligate pollinations; thus, they function as staminate flowers. However, some short‐styled morphs in Mounts Katsuu‐dake and Oppa‐dake populations have no fertile pollens. No fruit was obtained from bagging experiments, indicating that P. rubra requires pollinators for its reproduction. In our pollinator observations, flies and short‐tongued wasps were the main visitors of the flowers of P. rubra. Thus, these insects are probably effective pollinators for P. rubra in the Ryukyu Islands. Considering the morphological features, the dioecy found in P. rubra is probably derived from distyly; however, no sufficient evidence is available showing that dioecy has evolved “directly” from distyly.     

Heteromorphic incompatibility and efficiency of pollination in two distylous Pentanisia species (Rubiaceae)

BACKGROUND AND AIMS: Distyly has been hypothesized to promote cross-pollination by reducing intrafloral and geitonogamous self-pollination, and enhancing intermorph pollination. Distylous plants typically display both reciprocal herkogamy and a heteromorphic incompatibility system, which allows mating only between morphs. Distyly and its pollination consequences were examined in two Pentanisia species with long-tubed flowers which are pollinated almost exclusively by butterflies. METHODS: Anther and stigma heights were measured to quantify reciprocal herkogamy. The type of incompatibility system was determined by observing pollen tubes and seed production following controlled hand pollination. Pollen loads on pollinators and stigmas were also examined to assess the efficiency of intermorph pollen flow. KEY RESULTS: Pentanisia prunelloides and P. angustifolia exhibit reciprocal herkogamy and a host of ancillary dimorphisms, including pollen colour, exine sculpturing, stigmatic papilla shape and floral-tube pubescence. Controlled hand-pollinations revealed the presence of a strong heteromorphic incompatibility system in both species. The site of incompatibility differed between the morphs; intramorph pollen tubes were blocked in the style of the short-styled morph and on the stigmatic surface of the long-styled morph. Butterflies carried pollen from the short- and long-styled morphs primarily on their head and proboscis, respectively. Natural pollination resulted in a higher proportion of pollen transfer from long- to short-styled plants than vice versa. Nevertheless, fruit set did not differ between morphs. CONCLUSIONS: Both Pentanisia species are fully distylous. Reciprocal herkogamy results in pollen from the two morphs being carried on different locations on pollinators' bodies, which in turn promotes intermorph pollination. Intramorph pollination does not result in fertilization, because of an effective heteromorphic incompatibility system.     

国产耳草属(茜草科)一新种——蕴璋耳草

报道了中国茜草科Rubiaceae耳草属耳草组Hedyotis sect. Hedyotis植物的一个新种——蕴璋耳草H. koiana R. J. Wang。本新种同丹草H. herbacea L.和松叶耳草H. pinifolia Wall. ex G. Don因均具有较窄的叶片和仅顶部开裂的蒴果而相似, 但本种因具线形的叶片以及顶生和上部腋生的聚伞花序而不同于丹草, 与松叶耳草的不同之处在于蕴璋耳草具有较长的花梗和疏松的花序以及花冠管内部无毛。     

Macrophylogenetic analyses of the gain and loss of self-incompatibility in the Asteraceae

The self-incompatibility (SI) status of 571 taxa from the Asteraceae was identified and the taxa were scored as having SI, partial SI or self-compatibility (SC) as their breeding system. A molecular phylogeny of the internal transcribed spacer (ITS) region was constructed for 211 of these taxa. Macrophylogenetic methods were used to test hypotheses concerning the ancestral state of SI in the Asteraceae, the gain and loss of SI, the irreversibility of the loss of SI and the potential for partial SI or SC to be terminal states. The ancestral breeding system in the family could not be resolved. Both maximum likelihood and parsimony analyses indicated that transitions among all breeding system states provide the best fit to the data and that neither partial SI nor SC is a terminal state. Furthermore, the data indicated that the loss of SI is not irreversible, although breeding system evolution has been more dynamic in some clades than in others. These results are discussed within the context of evidence for the gain and loss of SI, the evolutionary role of partial SI and methodological assumptions of tests of breeding system evolution.     

Cryptic dioecy in Mussaenda pubescens (Rubiaceae): a species with stigma-height dimorphism

Background and Aims

Evolutionary transitions from heterostyly to dioecy have been proposed in several angiosperm families, particularly in Rubiaceae. These transitions involve the spread of male and female sterility mutations resulting in modifications to the gender of ancestral hermaphrodites. Despite sustained interest in the gender strategies of plants, the structural and developmental bases for transitions in sexual systems are poorly understood.

Methods

Here, floral morphology, patterns of fertility, pollen-tube growth and floral development are investigated in two populations of the scandent shrub Mussaenda pubescens (Rubiaceae), native to southern China, by means of experimental and open-pollinations, light microscopy, fluorescence microscopy and scanning electron microscopy combined with paraffin sectioning.

Key Results

Mussaenda pubescens has perfect (hermaphroditic) flowers and populations with two style-length morphs but only weak differentiation in anther position (stigma-height dimorphism). Experimental pollinations demonstrated that despite morphological hermaphroditism, the species is functionally dioecious. The long-styled (L) morph possesses sterile pollen and functions as a female, whereas the short-styled (S) morph is female sterile and functions as a male. Self- and intra-morph pollinations of the S-morph were consistent with those expected from dimorphic incompatibility. The two populations investigated were both S-morph (male) biased. Investigations of early stages of floral development indicated patterns typical of hermaphroditic flowers, with no significant differences in organ growth between the floral morphs. Meiosis of microspore mother cells was of the simultaneous type with tetrads isobilateral in shape. The tapetal cells in anther walls of the L-morph became vacuolized during meiosis I, ahead of the uninucleate microspore stage in the S-morph. In the L-morph, the microspore nucleus degenerated at the tetrad stage resulting in male sterility. Microsporogenesis and male gametophyte development was normal in the S-morph. Failure in the formation of megaspore mother cells and/or the development of megagametophytes resulted in female sterility in the S-morph, compared with normal megasporogenesis in the L-morph.

Conclusions

In M. pubescens, cryptic dioecy has evolved from stigma-height dimorphism as a result of morph-specific sterility mutations.