峨眉山玉叶金花属一新种

描述了四川峨眉山茜草科（玉叶金花属）一新种,即峨眉玉叶金花。     

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.     

中国玉叶金花属一新记录种——长瓣玉叶金花

报道中国茜草科(Rubiaceae)玉叶金花属一新记录种——长瓣玉叶金花(Mussaenda longipetala H. L. Li)。该种在形态上与尾裂玉叶金花(M. caudatiloba D. Fang)和狭瓣玉叶金花(M. lancipetal X. F. Deng & D. X. Zhang)相似,但区别在于叶片长圆状卵形或椭圆状卵形,托叶早落,正常的萼裂片长6~8 mm,花冠管长约3 cm,裂片披针形,长约12 mm。目前仅知分布于越南北部的广宁省和中国的广西北部湾沿海地区。凭证标本存放于广西植物标本馆(IBK)。     

Chemical constituents of Mussaenda erythrophylla Schumach. & Thonn. (Rubiaceae) and their chemophenetic significance

The chemical investigation of the CH₂Cl₂/MeOH (1:1) extract from the aerial part of Mussaenda erythrophylla Schumach. & Thonn. (Rubiaceae) resulted in the isolation of sixteen known compounds (1–16) distributed in coumarins, flavonoid glucosides, quinic acid derivatives, triterpenoids, monoglycerid, steroids, tetraterpenoid and polyol. The structures of the compounds were determined by spectrometric and spectroscopic analysis including MS and NMR data followed by their comparison with reported ones in the literature. The chemophenetic significance of the isolated compounds was discussed. The crude extract and some of the isolated compounds were assessed in vitro for their antileishmanial, cytotoxic and antiplasmodial activities. The crude extract of M. erythrophylla showed moderate antileishmanial activity (IC₅₀ = 61.6 μg/mL) while the hexane soluble fraction showed good antileishmanial activity (IC₅₀ = 31.06 μg/mL) compared to the reference drug amphotericin B (IC₅₀ = 0.11 μM). Compounds 11 and 9 also exhibited potent antileishmanial activity (IC₅₀ = 53.7–52.0 μM). The crude extract as well as the ethyl acetate soluble fraction also exhibited good antiplasmodial activity (IC₅₀ = 7.43 ± 0.00 μg/mL and 14.49 ± 2.96 μg/mL respectively), while compounds 11, 15 and 16 showed weak activity with IC₅₀ > 20 μM compared to the reference drug artemisinin (IC₅₀ = 0.014 ± 0.001 μM).     

Somatic embryogenesis and shoot proliferation of Mussaenda cultivars

Midrib sections of Mussaenda 'Queen Sirikit', 'Do?a Luz', and 'Do?a Hilaria' were cultured on Murashige and Skoog medium (MS) supplemented with 87.7 mM sucrose, 5 g agar l⁻¹, 0, 5, 10 or 20 μM indole-3-acetic acid (IAA) and 0, 0.5, 1, 2.5, 5, 10, 25 or 50 μM 6-benzyladenine (BA). In addition, aseptic 5 mm shoot tips from 'Do?a Luz' cultures were excised and cultured on MS basal salts, 0.6 mM myo-inositol, 1.2 μM thiamine-HCl, 87.7 mM sucrose, 7 g agar l⁻¹, 0, 2.5, 5, 10, 20, or 40 μM BA, 0 or 1 μM α-naphthaleneacetic acid (NAA) and 0 or 217 μM adenine sulfate at pH 5.8. Calluses began to develop after two weeks at the cut ends of midribs when cultured on a medium containing IAA. Somatic embryos first appeared at eight weeks but only on 'Queen Sirikit' callus. After 15 weeks, the average number of somatic embryos produced per tube decreased as the IAA concentration increased from 0 to 20 μM. BA concentrations between 5.0 and 10.0 μM resulted in the largest number of somatic embryos per tube. After six weeks, the total, axillary and adventitious number of 'Do?a Luz' shoots increased as the BA concentration in the culture medium increased from 0 to 20 μM. Average shoot length and fresh weight decreased from 0 to 40 μM BA. The addition of NAA to the culture medium reduced shoot number. Adenine sulfate in the presence of BA reduced the total number of shoots. An ideal medium for proliferating the largest number of 'Do?a Luz' shoots would be a MS medium supplemented with 10–20 μM BA. This revised version was published online in June 2006 with corrections to the Cover Date.     

Exploration of Phytoconstituents from Mussaenda roxburghii and Studies of Their Antibiofilm Effect

In the context of ethno botanical importance with no phytochemical investigations, Mussaenda roxburghii have been investigated to explore it's phytoconstituents and studies of their antibiofilm activity. Four compounds have been isolated from the aerial parts of this plant and were characterized as 2α,3β,19α,23‐tetrahydroxyurs‐12‐en‐28‐oic acid ( 1 ), β‐sitosterol glucoside ( 4 ), lupeol palmitate ( 5 ), and myoinositol ( 6 ). All these compounds were tested for antibacterial and antibiofilm activity against Pseudomonas aeruginosa. Compound 1 exhibited three times more antibiofilm activity with minimum inhibitory concentration (MIC) at 0.74 mm compared to that of streptomycin. Molecular docking studies exhibited a very high binding affinity of 1 with P. aeruginosa quorum sensing proteins and motility associated proteins viz. LasR and PilB, PilY1, PilT, respectively. Compound 1 was also found to be non‐cytotoxic against sheep RBC and murine peritoneal macrophages at selected sub‐MIC doses.     

玉叶金花的组织培养和植株再生

1　植物名称　玉叶金花 (Ｍｕｓｓａｅｎｄａｐｕｂｅｓｃｅｎｓ)。2　材料类别　嫩茎、幼叶。3　培养条件　以ＭＳ为基本培养基。诱导愈伤组织附加 :( 1 )ＮＡＡ 0 .2ｍｇ·Ｌ- 1 (单位下同 ) ＫＴ0 .2 5 6 ＢＡ 0 .1 ;( 2 )ＮＡＡ 0 .5 ＫＴ 0 .2 5 6 ＢＡ0 .1 ;( 3)ＮＡＡ 0 .5 6 ＢＡ 0 .1 ;( 4 ) 2 ,4 Ｄ 0 .2 ＫＴ0 .1。继代培养基附加 :( 5 ) 6 ＢＡ 4 ＫＴ0 .2 5 ＩＡＡ 0 .5。不定芽诱导及增殖培养基附加 :( 6)6 ＢＡ 4 ＫＴ 0 .5 ＩＡＡ 0 .1。生根培养基 :( 7)1 /2ＭＳ ＩＢＡ 0 .5。上述培养基均含 0 .7%琼脂、3%蔗…     

Two new species of Mussaenda (Rubiaceae) from Panay Island,Philippines

Two new species of Mussaenda (Rubiaceae) from Aklan, Panay, Philippines are described and illustrated. Mussaenda ustii sp. nov. is distinct by its long pedicel (up to 7 mm), yellow with white margins corolla lobes forming a star and recurved stigma lobes which are always semi‐ or distinctly exserted in long‐styled morphs. Mussaenda viridiflora sp. nov. is characterized by its white, sweet‐scented corolla lobes, which are green tinged on the median ridges and bases, and strongly reflexed calyx lobes. A discussion of the relationships of the new taxa to closely related Philippine Mussaenda is provided. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 158 , 87–92.     

玉叶金花一新变种

报道了茜草科玉叶金花属玉叶金花一新变种,即白花玉叶金花Mussaenda pubescens Ait．f.var．alba X．F．Denget D．X．Zhang,var．nov．     

Somatic embryogenesis in callus culture of Mussaenda erythrophylla cvs. Queen Sirikit and Rosea

Somatic embryogenesis was achieved from mid-rib and internodal calluses of Mussaenda erythrophylla L. cvs. Queen Sirikit and Rosea cultured on Murashige and Skoog basal medium containing 8.9 M BA+0.57 M IAA+10 mg l^-1 ascorbic acid. Clumps of somatic embryos were separated and grown into complete plantlets when transferred to 1/2 MS medium+37 M adenine sulphate with 2% (w/v) sucrose.     

国产玉叶金花属(茜草科)的三个新异名

澄清了中国产玉叶金花属Mussaenda 2种1变型的分类学位置, 分别将胀管玉叶金花M. inflata Hsue &; H. Wu、异形玉叶金花M. anomala Li和灵仙玉叶金花M. pubescens Ait. f. forma clematidiflora Chun ex Hsue &; H. Wu作为粗毛玉叶金花M. hirsutula Miq.、大叶白纸扇M. esquirolii Lévl.和玉叶金花M. pubescens Ait. f.的新异名处理。     

Mussaenda yunnanensis sp. nov. (Rubiaceae), a new functionally dioecious species from Yunnan,China

Mussaenda yunnanensis, a new dioecious species of Rubiaceae from Yunnan Province, China, is described and illustrated. The new species can be recognized by its slender stem, congested‐cymose inflorescences and long corolla tubes. Differences between M. yunnanensis and two morphologically similar species (M. pubescens and M. antiloga) are presented. We also provide a key to all dioecious species of Mussaenda in China. The delimitation of the new species is further supported by molecular phylogenetic analyses based on eight plastid loci.     

Pre-and post-zygotic reproductive isolation between co-occurring Mussaenda pubescens var.alba and M. shikokiana(Rubiaceae)

Reproductive isolation is a fundamental requirement for speciation and includes several sequential stages.Few studies have determined the relative contributions of pre-and post-zygotic reproductive isolation in plants,especially between relative species with clear differentiation in flower form.To investigate the mechanisms responsible for reproductive isolation in sympatric Mussaenda pubescens var.alba and Mussaenda shikokiana(Rubiaceae)in Guangxi Province,China,we made observations of flowering phenology,patterns of insect visitation,and conducted pollination experiments,including artificial hybridization.The two species had overlapping flowering times and were pollinated by overlapping pollinators;however,their relative importance differed significantly with M.pubescens visited more commonly by bees and M.shikokiana more frequently by butterflies.Using vegetative and floral characters and molecular evidence based on nuclear ribosomal internal and external transcribed spacer regions we detected seven naturally occurring hybrids among a sample of approximately 125 individuals.Hybrids werecharacterized by morphologies that most closely resembled their maternal parents based on chloroplast evidence.Studies of artificially synthesized and natural hybrids demonstrated that hybrid seed had very low germination rates and naturally occurring hybrids exhibited pollen sterility.Post-zygotic reproductive isolating mechanisms play a primary role in limiting gene exchange between co-occurring species and maintaining species integrity in areas of sympatry.     

Mussaenda epiphytica sp. nov. (Rubiaceae), an epiphytic shrub from cloud forest of the Bakossi Mts,western Cameroon

Mussaenda epiphytica Cheek is described as a new species, remarkable for being a cloud forest canopy epiphytic shrub in a genus of terrestial climbers and straggling shrubs. Attention is drawn to its adaptations to the epiphytic habit. The species appears to be endemic to the submontane evergreen forests of the Bakossi Mts, including Mt Kupe, in Cameroon. Its conservation status is assessed as ‘Vulnerable’ using IUCN criteria.     

Reproductive isolation between sympatric sister species,Mussaenda kwangtungensis and M. pubescens var. alba

Reproductive isolation de fi nes the biological species concept and plays a key role in the formation and maintenance of species. The relative contributions of different isolating stages has been suggested to be closely associated with phylogenetic relatedness. Few studies have focused on the relative contributions of pre- versus postzygotic mechanisms, and even fewer have been conducted under strict phylogenetic frameworks. Pre- and post-zygotic reproductive isolation stages have been investigated in the sister species Mussaenda kwangtungensis and M. pubescens var. alba. The two species have partly overlapping distribution ranges and fl owering times, while the principal pollinators differed strikingly for them, demonstrating strong pre-zygotic isolations. Natural hybrids were detected by simple sequence repeat markers and their maternal parents were identi fi ed based on chloroplast gene sequences. Five out of 81 individuals were suggested to be hybrids that fall into the categories F2, BC1, and BC2 by theNew Hybrids analysis. Interspeci fi c crossings resulted in signi fi cantly reduced fruit set and seed germination rates.Phylogenetic analysis revealed short Kimura-2-parameter distance between M. kwangtungensis and M. pubescens var.alba. These fi ndings strongly supported the hypothesis that for species with a closer phylogenetic relationship, prezygotic isolation plays an important part in limiting gene exchange in sympatric areas.     

In vitro propagation of Mussaenda erythrophylla Schum and Thom cv. scarlet through multiple shoot regeneration

Axillary bud explants were induced to form shoots on Murashige and Skoog's (MS)' basal medium. Best yield (9 shoots per explant) was obtained when the medium was supplemented with adenine sulphate (40 mg/L) and 6-benzylaminopurine (2.25 mg/L). The shoots were rooted on half strength MS basal medium supplemented with indole butyric acid (0.5 mg/L) and having thiamin-HCl (800 mg/L). Regenerated plantlets were successfully acclimatized. This is the first report of micropropagation in the genus Mussaenda without callus intervention.     

Pollen–ovule ratios are strongly correlated with floral reciprocity,in addition to sexual system,in Mussaenda (Rubiaceae)

Heterostyly is a floral polymorphism that increase inter‐morph pollen transfer and promote disassortative mating. Breakdown of heterostyly has happened many times, either leading to dioecy or monomorphism. Mussaenda is a genus with diverse sexual systems including distyly, dioecy, floral monomorphism, and homostyly, making it an ideal system to study the evolution of floral traits and their relationship with sexual system shifts. Here, floral traits and pollen–ovule (P/O) ratios were estimated and used to test hypotheses about the relationships among P/O ratios, floral trait evolution, and sexual system shifts. Our results revealed that there is no significant difference of reciprocity in upper level sexual organs between species with different sexual systems. The reciprocity indices of the lower level sexual organs, however, are smaller in species with functional dioecy than in those with distyly. P/O ratios in dimorphic Mussaenda species were relatively lower than in monomorphic outcrossing species, but did not differ significantly between species with distyly and functional dioecy. Populational P/O ratios were negatively correlated with reciprocity index in the dimorphic species. We suggest that the loss of function in lower level organs in species with functional dioecy has resulted from less strict reciprocity. The relationship between P/O ratios and reciprocity indices strongly support that efficient disassortative pollination of distylus flowers may have promoted evolution towards low P/O ratios.