花香的生物合成、调控及基因工程研究进展

花香能提高观赏植物的审美特性,并且在植物的繁衍中起着重要作用。近年来,随着分子生物学的发展,花香分子水平的研究呈现加速发展的趋势,已成为当前的一大研究热点。该文主要论述了花香的生物合成途径及关键酶基因、分子水平的调控和共调控探索、花香基因工程策略,以期为花香性状改良提供参考。     

植物次生代谢途径的遗传操作

植物次生代谢产物种类极其丰富,是人类的宝贵资源,这些产物及其合成途径相关酶具有空间特异性分布的特征。植物次生代谢途径的调控是个复杂的过程,受代谢产物水平、多酶复合物相互作用等多种因素的影响。通过遗传操作改造代谢过程,调控产物在植物体内的含量,是一条切实可行和具有广阔发展空间的途径。目前,改造植物次生代谢途径可以采取单基因操作和多基因操作两种策略进行。     

类胡萝卜素生物合成相关基因的克隆及其遗传工程的研究进展

类胡萝卜素具有重要的生物学功能,尤其对人体健康有着更重要的作用,近年来一直是研究的热点。综述了类胡萝卜素生物合成途径及相关基因的分离,以及运用这些基因提高微生物和植物中类胡萝卜素含量的遗传工程研究进展。     

花颜色和花气味的量化研究方法

花颜色和花气味是花部构成的重要内容。在已开展的传粉生态学研究中对二者的报道主要是描述性的,而其量化研究可以为揭示传粉机制提供有力的实验证据。本文主要介绍了花颜色的测量和标定方法,包括比色卡、分光色差仪和便携式光谱仪等;花气味的采集方法,包括动态顶空套袋-吸附采集法、吸附-溶剂洗脱法和固相微萃取法等;花气味的检测和分析方法,包括气相色谱-质谱联用仪分析和电子鼻型超速气相色谱仪分析等;以及昆虫行为学实验方法,包括气相色谱-昆虫触角电位联用技术、Y型嗅觉仪和飞行箱实验等。科研人员可以根据实验材料的特点和实验目的选择适合的量化研究方法。     

Evidence for positive selection on the floral scent gene isoeugenol-O-methyltransferase

Isoeugenol-O-methyltransferase (IEMT) is an enzyme involved in the production of the floral volatile compounds methyl eugenol and methyl isoeugenol in Clarkia breweri (Onagraceae). IEMT likely evolved by gene duplication from caffeic acid-O-methyltransferase followed by amino acid divergence, leading to the acquisition of its novel function. To investigate the selective context under which IEMT evolved, maximum likelihood methods that estimate variable d(N)/d(S) ratios among lineages, among sites, and among a combination of both lineages and sites were utilized. Statistically significant support was obtained for a hypothesis of positive selection driving the evolution of IEMT since its origin. Subsequent Bayesian analyses identified several sites in IEMT that have experienced positive selection. Most of these positions are in the active site of IEMT and have been shown by site-directed mutagenesis to have large effects on substrate specificity. Although the selective agent is unknown, the adaptive evolution of this gene may have resulted in increased effectiveness of pollinator attraction or herbivore repellence.     

A simple floral fragrance and unusual osmophore structure in Cyclopogon elatus (Orchidaceae)

We studied gland morphology, anatomy and the chemical composition of the floral fragrance in the sweat bee-pollinated orchid Cyclopogon elatus . This is apparently the first such analysis for any Cyclopogon species, and one of very few studies in which both odour and osmophore are characterised in a nectar-rewarding orchid. Structures responsible for floral scent production were localised with neutral red staining and histochemical assays for lipids and starch. Their morphology and anatomy were studied with scanning electron microscopy and light microscopy thin sections, respectively. Fragrance samples were collected using SPME fibres and analysed with GC-MS. Anatomical evidence suggests that two parallel oval-shaped patches of unicellular trichomes on the abaxial surface of the labellum are osmophores. These are rich in stored lipids, while the parenchyma surrounding the vascular bundles contains starch. Only freshly opened flowers produced odours, while buds and withered flowers lacked scent. The chemical composition of the odour was dominated (>99.8%) by a single compound, trans-4,8-dimethyl-nona-1,3,7-triene (DMNT). Gland anatomy and position on the outside of the perianth are unusual for scent glands in general. The presence of DMNT, a nearly ubiquitous compound in herbivore-induced vegetative emissions and one of the major floral volatiles of Yucca , is not surprising in view of hypotheses on the evolutionary origin of flower scents, suggesting that wound volatiles are utilised as kairomonal attractants by florivores whose activities result in pollination.     

花对称性的研究进展

花对称性(floral symmetry)是被子植物花部结构的典型特性之一,主要有辐射对称和两侧对称两种形式。被子植物初始起源的花为辐射对称,而两侧对称的花则是由辐射对称的花演变而来。两侧对称的花部结构是被子植物进化过程中的一个关键的革新,被认为是物种形成和分化的关键推动力之一。近年来有关花对称性的形成和进化机制的研究在植物学科的不同领域均取得了长足的进展。本文综述了花对称性在发育生物学、传粉生物学、生殖生态学及分子生物学等方面的研究进展。两侧对称形成于被子植物花器官发育的起始阶段,随后贯穿整个花器官发育过程或者出现在花器官发育后期的不同阶段。花器官发育过程中一种或多种类型器官的败育以及特异性花器官结构的形成是两侧对称形成的主要原因。研究表明,在传粉过程的不同阶段,花对称性均会受到传粉昆虫介导的选择作用。相比辐射对称的花,两侧对称的花提高了特异性传粉者的选择作用,增加了花粉落置的精确性,进而确保了其生殖成功。花对称性的分子机理已经在多种双子叶植物中进行了深入的研究。现有的证据表明,CYC同源基因在花对称性的分子调控方面起着非常重要的作用。花对称性在被子植物进化过程中是如何起源,与其他花部构成之间是否协同作用,一些不符合一般模式的科属其花对称性的形成机制等都是今后要进一步研究的命题。     

高等植物成花分子机理研究现状及展望

以拟南芥、金鱼草为例,介绍了近几年植物成花（包括成花诱导、花序分生组织的组成、花发端、花器官发生及发育）研究的一些进展,着重介绍了成花过程中基因的表达,调控与生理功能。     

Deceptive pollination in two subspecies of Disa spathulata (Orchidaceae) differing in morphology and floral fragrance

The non-rewarding flowers of Disa spathulata (L.f) Sw. have a highly elongated scent-producing lip that varies in size and form between the two subspecies of this orchid. We investigated whether this unusual morphology is associated with the evolution of a specialized scent-based pollination system. Field observations carried out in South Africa showed that flowers of D. spathulata are pollinated solely by bees belonging to the genus Tetraloniella (Anthophoridae). Flowers of D. spathulata subsp. spathulata were visited by Tetraloniella brevikeraia, while flowers of D. spathulata subsp. tripartita (Lindl.). H. P. Linder were visited by Tetraloniella junodi. The floral fragrance of D. spathulata is emitted by the lip blade and differs markedly between the two subspecies (only 24 [42.1] of the 57 compounds identified were shared). Fragrance of D. spathulata subsp spathulata is dominated by the fatty acid derivatives decyl actetate, octanol, and decanol, while that of D. spathulata subsp. tripartita is dominated by the terpenoids (E) - ocimene, caryophyllene, and (E) nerolidol. Both male and female Tetraloniella bees were strongly attracted to cut flowers of D. spathulata subsp spathulata, even at sites where the orchid does not naturally occur. Bees visit the orchids repeatedly despite the lack of rewards in their flowers. Sexual deception in D. spathulata can be excluded by the attraction of both male and female bees, and yet the manner in which bees are attracted seems too intense and species-specific to be characterized as food-deception. This implies the existence in D. spathulata of a system of scent-based deception of insects that has not been described previously in plants.     

解淀粉芽孢杆菌分子遗传操作及其应用研究进展

解淀粉芽孢杆菌是FDA认定的安全级(generally recognized as safe,GRAS)菌株,在工业酶制剂、高分子聚合物、大宗化学品、绿色生物农药等方面的生产具有突出的优势.近年来,随着解淀粉芽孢杆菌的分子遗传操作技术越来越成熟,对利用该菌开发成微生物发酵平台化菌株用于合成生物学制造领域提出了更迫切的需...     

Integrating floral scent, pollination ecology and population genetics

1 . Floral scent is a key factor in the attraction of pollinators. Despite this, the role of floral scent in angiosperm speciation and evolution remains poorly understood. Modern population genetic approaches when combined with pollination ecology can open new opportunities for studying the evolutionary role of floral scent.
2 . A framework of six hypotheses for the application of population genetic tools to questions about the evolutionary role of floral scent is presented. When floral volatile chemistry is linked to pollinator attraction we can analyse questions such as: Does floral volatile composition reflect plant species boundaries? Can floral scent facilitate or suppress hybridization between taxa? Can the attraction of different pollinators influence plant mating systems and pollen-mediated gene flow? How is population genetic structure indirectly influenced by floral scent variation?
3 . The application of molecular tools in sexually deceptive orchids has confirmed that volatile composition reflects species boundaries, revealed the role of shared floral odour in enabling hybridization, confirmed that the sexual attraction mediated by floral odour has implications for pollen flow and population genetic structure and provided examples of pollinator-mediated selection on floral scent variation. Interdisciplinary studies to explore links between floral volatile variation, ecology and population genetics are rare in other plant groups.
4 . Ideal study systems for future floral scent research that incorporate population genetics will include closely related taxa that are morphologically similar, sympatric and co-flowering as well as groups that display wide variation in pollination mechanisms and floral volatiles.     

Do pollinators simultaneously select for inflorescence size and amount of floral scents? An experimental assessment on Escallonia myrtoidea

Abstract Correlation among phenotypic traits may be explained by correlational selection, the simultaneous selection of more than one trait, or by genetic and/or developmental factors. In Escallonia myrtoidea, a tree with scented flowers from central Chile, inflorescence size and the amount of floral scents were positively correlated. Independent manipulation of scent and inflorescence size in a factorial design was used to assess the occurrence of pollinator‐mediated correlational selection. Dependency on pollinators for seed set was also assessed. If pollinator‐mediated correlational selection occurs, nonadditive effects of both traits are expected, albeit only when the effect of manipulating the state of such traits is disadvantageous with respect to the naturally occurring inflorescences, and provided that plants are not limited by pollinators for seed set and pollen export. Escallonia myrtoidea was very strongly pollinator‐limited for seed set and pollen export. Pollinator‐mediated additive effects were not observed in the frequency of visits by pollinators, pollen export, and seed set of E. myrtoidea after experiencing scent and inflorescence size manipulations. Consequently, there was no support for pollinator‐mediated correlational selection between those traits, suggesting the prevalence of genetic and/or developmental factors.     

Covariance and decoupling of floral and vegetative traits in nine Neotropical plants: a re-evaluation of Berg's correlation-pleiades concept

Nearly forty years ago R. L. Berg proposed that plants with specialized pollination ecology evolve genetic and developmental systems that decouple floral morphology from phenotypic variation in vegetative traits. These species evolve separate floral and vegetative trait clusters, or as she termed them, "correlation pleiades." The predictions of this hypothesis have been generally supported, but only a small sample of temperate-zone herb and grass species has been tested. To further evaluate this hypothesis, especially its applicability to plants of other growth forms, we examined the patterns of phenotypic variation and covariation of floral and vegetative traits in nine species of Neotropical plants. We recognized seven specific predictions of Berg's hypothesis. Our results supported some predictions but not others. Species with specialized pollination systems usually had floral traits decoupled (weak correlation; Canna and Eichornia) or buffered (relationship with shallow proportional slope; Calathea and Canna) from variation in vegetative traits. However, the same trend was also observed in three species with unspecialized pollination systems (Echinodorus, Muntingia, and Wedelia). One species with unspecialized pollination (Croton) and one wind-pollinated species (Cyperus) showed no decoupling or buffering, as predicted. While species with specialized pollination usually showed lower coefficients of variation for floral traits than vegetative traits (as predicted), the same was also true of species with unspecialized or wind pollination (unlike our prediction). Species with specialized pollination showed less variation in floral traits than did species with unspecialized or wind pollination, as predicted. However, the same was true of the corresponding vegetative traits, which was unexpected. Also in contrast to our prediction, plants with specialized pollination systems did not exhibit tighter phenotypic integration of floral characters than did species with generalized pollination systems. We conclude that the patterns of morphological integration among floral traits and between floral and vegetative traits tend to be species specific, not easily predicted from pollination ecology, and generally more complicated than R. L. Berg envisaged.     

Pre-adaptations and the evolution of pollination by sexual deception: Cope's rule of specialization revisited

Pollination by sexual deception is arguably one of the most unusual liaisons linking plants and insects, and perhaps the most illustrative example of extreme floral specialization in angiosperms. While considerable progress has been made in understanding the floral traits involved in sexual deception, less is known about how this remarkable mimicry system might have arisen, the role of pre-adaptations in promoting its evolution and its extent as a pollination mechanism outside the few groups of plants (primarily orchids) where it has been described to date. In the Euro-Mediterranean region, pollination by sexual deception is traditionally considered to be the hallmark of the orchid genus Ophrys. Here, we introduce two new cases outside of Ophrys, in plant groups dominated by generalized, shelter-mimicking species. On the basis of phylogenetic reconstructions of ancestral pollination strategies, we provide evidence for independent and bidirectional evolutionary transitions between generalized (shelter mimicry) and specialized (sexual deception) pollination strategies in three groups of flowering plants, and suggest that pseudocopulation has evolved from pre-adaptations (floral colours, shapes and odour bouquets) that selectively attract male pollinators through shelter mimicry. These findings, along with comparative analyses of floral traits (colours and scents), shed light on particular phenotypic changes that might have fuelled the parallel evolution of these extraordinary pollination strategies. Collectively, our results provide the first substantive insights into how pollination sexual deception might have evolved in the Euro-Mediterranean region, and demonstrate that even the most extreme cases of pollinator specialization can reverse to more generalized interactions, breaking ‘Cope''s rule of specialization’.     

Emitted and endogenous floral scent compounds of Prunus mume and hybrids

Prunus mume is the only species of Prunus known to produce a strong floral fragrance. Most interspecific hybrids between P. mume and other species of Prunus lack the fragrance. The analysis of variations in emitted and endogenous compounds among genetically close cultivars is a powerful approach for revealing the mechanisms underlying floral scent emission. Compounds emitted by flowers from five cultivars were collected using the static headspace method, and endogenous compounds in the flowers were extracted with ethyl acetate. Samples were analysed quantitatively and qualitatively using gas chromatography-mass spectrometry. The result showed that benzenoids were the dominant compounds, of which benzyl acetate was the principal component contributing to the floral scent of P. mume. A clustering analysis of the floral volatiles from the different cultivars suggested that the scent traits of hybrids are related to the taxonomic relationship between their parents. The correlations between the amount of the endogenous and emitted compounds revealed that benzyl acetate had a stronger tendency to be volatile than the other compounds and the volatilisation rate of volatile compounds varied greatly among different cultivars. The importance of the biosynthetic pathway and the function of benzaldehyde are discussed.     

木质素的生物合成及其调控研究进展

木质素是植物体中仅次于纤维素的一种重要大分子有机物质,具有重要生物学功能,其3种主要单体的生物合成途径已经基本清楚。从木质素生物合成及基因工程在调控木质素生物合成中的作用等方面的研究进展进行了综述,并提出了存在的问题及对策。     

The evolution of floral biology in basal angiosperms

In basal angiosperms (including ANITA grade, magnoliids, Choranthaceae, Ceratophyllaceae) almost all bisexual flowers are dichogamous (with male and female functions more or less separated in time), and nearly 100 per cent of those are protogynous (with female function before male function). Movements of floral parts and differential early abscission of stamens in the male phase are variously associated with protogyny. Evolution of synchronous dichogamy based on the day/night rhythm and anthesis lasting 2 days is common. In a few clades in Magnoliales and Laurales heterodichogamy has also evolved. Beetles, flies and thrips are the major pollinators, with various degrees of specialization up to large beetles and special flies in some large-flowered Nymphaeaceae, Magnoliaceae, Annonaceae and Aristolochiaceae. Unusual structural specializations are involved in floral biological adaptations (calyptras, inner staminodes, synandria and food bodies, and secretory structures on tepals, stamens and staminodes). Numerous specializations that are common in monocots and eudicots are absent in basal angiosperms. Several families are poorly known in their floral biology.     

Evolutionary breakdown of distyly to homostyly is accompanied by reductions of floral scent in Primula oreodoxa

Reproductive traits that function in pollinator attraction may be reduced or lost during evolutionary transitions from outcrossing to selfing. Although floral scent plays an important role in attracting pollinators in outcrossing species, few studies have investigated associations between floral scent variation and intraspecific mating system transitions. The breakdown of distyly to homostyly represents a classic example of a shift from outcrossing to selfing and provides an opportunity to test whether floral fragrances have become reduced and/or changed in composition with increased selfing. Here, we evaluate this hypothesis by quantifying floral volatiles using gas chromatography-mass spectrometry in two distylous and four homostylous populations of Primula oreodoxa Franchet, a perennial herb from SW China. Our analysis revealed significant variation of volatile organic compounds (VOCs) among populations of P. oreodoxa. Although there was no difference in VOCs between floral morphs in distylous populations as predicted, we detected a substantial reduction in VOC emissions and the average number of scent compounds in homostylous compared with distylous populations. A total of 12 compounds, mainly monoterpenoids and sesquiterpenoids, distinguished homostylous and distylous morphs; of these, (E)-β-ocimene was the most important in contributing to the difference in volatiles, with significantly lower emissions in homostyles. Our findings support the hypothesis that the transition from outcrossing to selfing is accompanied by the loss of floral volatiles. The modification to floral fragrances in P. oreodoxa associated with mating system change might occur because high selfing rates in homostylous populations result in relaxed selection for floral attractiveness.