ALLOZYME DIVERSITY AND GENETIC IDENTITY IN SCHIEDEA AND ALSINIDENDRON (CARYOPHYLLACEAE: ALSINOIDEAE) IN THE HAWAIIAN ISLANDS

Genetic diversity of allozymes, genetic identity based on allozyme variability, and phylogenetic relationships were studied with respect to breeding system diversity, population size, and island age in 20 of the 29 species of Schiedea and Alsinidendron (Caryophyllaceae: Alsinoideae), a monophyletic lineage endemic to the Hawaiian Islands. Average levels of genetic variability in Schiedea and Alsinidendron were comparable to or higher than those found in other Hawaiian lineages for which equivalent data are available [Bidens, Tetramolopium, and the silversword alliance (Asteraceae: Madiinae)] and similar to average values for species of dicots. Allozyme variability was strongly dependent on breeding system, which varies widely in the Hawaiian Alsinoideae. Species with autogamous breeding systems showed very low variability, measured as the number of alleles per locus, percent polymorphic loci, and mean heterozygosity per locus. Outcrossing hermaphroditic and dimorphic species (those with gynodioecious, subdioecious, and dioecious breeding systems) showed significantly higher genetic variability. Small population size was associated with lower values for all measures of genetic variability. Nearly half of the species occurring in small populations are also autogamous; thus, both factors may have influenced levels of genetic variability in these species. Founder effect was apparent in one species (Schiedea adamantis), which occurs in a single large population, has a gynodioecious breeding system but a very low genetic variability. Island age appeared to have little effect on genetic variability. Slightly lower values of genetic variability for species occurring on Kaua'i and O'ahu result primarily from the occurrence of autogamous Alsinidendron species on those islands. Values for Nei's genetic identity for different species pairs were 0.201–0.942, a far greater range than in Bidens, the silversword alliance, and Tetramolopium. Using UPGMA clustering, there was only moderate support for relationships detected through cladistic analysis. Nei's unbiased genetic identity (I) was greatest among species with outcrossing breeding systems, which for the most part clustered together. Nei's genetic identities for self-fertilizing species were low, indicating that these species are less similar to one another and to outcrossing species, regardless of their affinities based on cladistic analysis. Parsimony analysis of allele frequency data supported two clades also found in phylogenetic analyses using morphological and molecular data. Clades recognized in parsimony analysis of allele frequencies were those lineages containing selfing species, indicating that conditions favoring fixation of alleles occurred in ancestral species. In contrast, maintenance of high genetic diversity in outcrossing species interferes with recognition of phylogenetic relationships using allozyme variability.     

Genetical and biochemical evidence that the hydroxylation pattern of the anthocyanin B-ring in Silene dioica is determined at the p-coumaroyl-coenzyme a stage

In petals of Silene dioica, gene P controls the 3′-hydroxylation of the anthocyanin B-ring and the hydroxylation pattern of the hydroxycinnamoyl acyl group bound to the 4″'-hydroxyl group of rhamnose of anthocyanidin 3-rhamnosyl(1→6)glucoside-5-glucoside. In this paper, experiments are presented which show that gene P is involved in the hydroxylation of p-coumaroyl-CoA to caffeoyl-CoA, which is then used both as a precursor in anthocyanin biosynthesis and as a substrate for the final acylation.     

金铁锁根中的环肽成分

从云南民间重要的药用植物金铁锁（Ｐｓａｍｍｏｓｉｌｅｎｅ ｔｕｎｉｃｏｉｄｅｓ Ｗ．Ｃ．Ｗｕ ｅｔ Ｃ．Ｙ．Ｗｕ）的根中分离得到２个新的天然环二肽以及２个新的环八肽：金铁锁环肽Ａ和Ｂ（ｐｓａｍｍｏｓｉｌｅｎｉｎｓ Ａ ａｎｄ Ｂ）。它们的结构经光谱方法鉴定为ｃｙｃｌｏ（－Ａｌａ－Ａｌａ－）,ｃｙｃｌｏ（－Ｖａｌ－Ａｌａ－）,ｃｙｃｌｏ（－Ｐｒｏ１－Ｐｈｅ１－Ｐｒｏ２－Ｐｈｅ２－Ｐｈｅ３－Ａｌａ－ｐ     

Nectar sugar composition of European Caryophylloideae (Caryophyllaceae) in relation to flower length,pollination biology and phylogeny

Floral nectar composition has been explained as an adaptation to factors that are either directly or indirectly related to pollinator attraction. However, it is often unclear whether the sugar composition is a direct adaptation to pollinator preferences. Firstly, the lower osmolality of sucrose solutions means that they evaporate more rapidly than hexose solutions, which might be one reason why sucrose‐rich nectar is typically found in flowers with long tubes (adapted to long‐tongued pollinators), where it is better protected from evaporation than in open or short‐tubed flowers. Secondly, it can be assumed that temperature‐dependent evaporation is generally lower during the night than during the day so that selection pressure to secrete nectar with high osmolality (i.e. hexose‐rich solutions) is relaxed for night‐active flowers pollinated at night. Thirdly, the breeding system may affect selection pressure on nectar traits; that is, for pollinator‐independent, self‐pollinated plants, a lower selective pressure on nectar traits can be assumed, leading to a higher variability of nectar sugar composition independent of pollinator preferences, nectar accessibility and nectar protection. To analyse the relations between flower tube length, day vs. night pollination and self‐pollination, the nectar sugar composition was investigated in 78 European Caryophylloideae (Caryophyllaceae) with different pollination modes (diurnal, nocturnal, self‐pollination) using high‐performance liquid chromatography (HPLC). All Caryophylleae species (Dianthus and relatives) were found to have nectar with more than 50% sucrose, whereas the sugar composition of Sileneae species (Silene and relatives) ranged from 0% to 98.2%. In the genus Silene, a clear dichotomous distribution of sucrose‐ and hexose‐dominant nectars is evident. We found a positive correlation between the flower tube length and sucrose content in Caryophylloideae, particularly in day‐flowering species, using both conventional analyses and phylogenetically independent contrasts.     

Ecogeographic and genetic evaluation of endemic species in the Maritime Alps: the case of Moehringia lebrunii and M. sedoides (Caryophyllaceae)

Abstract

The Maritime Alps are one of the ‘hot spots’ in the Mediterranean basin. This study investigated two endemic plants, Moehringia lebrunii and Moehringia sedoides (Caryophyllaceae) in order to increase knowledge of the vegetation of this region, and to investigate possible conservation strategies. Ecogeographic surveys and molecular analyses were undertaken. Gene diversity, the Shannon index and G_ST were calculated within and among populations of the two species based on ISSR data. The populations of M. lebrunii had a density ranging between 0.04 and 0.86 individual/m² and a rather low inner genetic variability value. According to IUCN Red List Criteria, the current status of M. lebrunii is Endangered [EN B2ab(ii, iv)]. M. sedoides is an endemic of the SW Alps (not exclusive of the Maritime Alps), and is very abundant within the core of the range. Its range of occurrence is smaller than previously reported; nevertheless, the species is not under threat. This taxon showed a population density ranging between 0.03 and 0.58 individual/m². Genetic variability values revealed a high variation among the species. Only peripheral populations seemed to suffer from their segregated position. Thus, M. sedoides is to be considered Critically Endangered [CR B1ab(i, ii, iii, iv) + 2ab(i, ii, iii, iv)] for Italy according to Regional Guidelines.     

Phylogeography sheds light on the central–marginal hypothesis in a Mediterranean narrow endemic plant

Background and Aims

Understanding the factors that shape variation in genetic diversity across the geographic ranges of species is an important challenge in the effort to conserve evolutionary processes sustaining biodiversity. The historical influences leading to a central–marginal organization of genetic diversity have been explored for species whose range is known to have expanded from refugia after glacial events. However, this question has rarely been addressed for Mediterranean endemic plants of azonal habitats such as rocky slopes or screes. In this context, this comprehensive study examined molecular and field data from Arenaria provincialis (Caryophyllaceae), a narrow endemic plant of south-eastern France.

Methods

Across the whole geographic range, an investigation was made of whether high levels of abundance and genetic diversity (estimated from amplified fragment length polymorphism markers) are centrally distributed, to evaluate the relevance of the central–marginal hypothesis. Phylogeographic patterns inferred from chloroplast DNA (cpDNA) were used, applying Bayesian methods to test the influence of past biogeographic events. Multivariate analysis combining phylogeographic and ecological data was used to reveal the historical and ecological distinctiveness of populations.

Key Results

Despite the narrow distribution of A. provincialis, a high level of nucleotide variation is found within cpDNA loci, supporting its persistence throughout the Pleistocene period. The area characterized by the highest genetic diversity is centrally located. Structured phylogeography and Bayesian factor analysis supported the hypothesis that the central area of the distribution was the source of both westward and eastward migrations, probably during arid periods of the Pleistocene, and more recently was a crossroads of backward migrations. By contrast, the two areas located today at the range limits are younger, have reduced genetic diversity and are marginal in the ecological gradients.

Conclusions

This study highlights a case of strong population distinctiveness within a narrow range. Phylogeography sheds light on the historical role of the areas centrally situated in the distribution. The current range size and abundance patterns are not sufficient to predict the organization of genetic diversity.     

Fungal melanin inhibitor and related compounds from Penicillium decumbens

In Silene vulgaris (M.) G. cell culture three growth phases were distinguished, namely, a lag phase, an exponential phase and a stationary phase. Pectin termed silenan and an acidic arabinogalactan were isolated as cell wall polysaccharides of S. vulgaris callus at the different growth phases during culture. Production of silenan as the galacturonan (or rhamnogalacturonan) core was observed at the beginning of the exponential phase and at the stationary phase of the callus growth. Arabinogalactan, containing the galacturonic acid residues, is formed at the exponential phase followed by attachment to the core of silenan in the middle of the exponential phase. The arabinogalactan constituent of silenan appeared to be destroyed gradually at the stationary growth phase. The monosaccharide compositions of silenan and arabinogalactan were determined at various phases of the callus growth. Silenan was found to be formed in maximum amounts at the exponential phase of the cell growth. Insignificant alterations of the yields of acidic arabinogalactan were found during culture while total productivity per litre of medium and rate of production per day of arabinogalactan were found to be maximal at the exponential phase of growth.     

Metabolism of galactosyl-oligosaccharides in Stellaria media - Discovery of stellariose synthase, a novel type of galactosyltransferase

The raffinose family oligosaccharides (RFOs), including raffinose (Gal-α(1 → 6)-Glc-α(1 → 2)β-Fru), stachyose (Gal-α(1 → 6)-Gal-α(1 → 6)-Glc-α(1 → 2)β-Fru) and higher degree of polymerization RFOs are the most widespread galactosyl-oligosaccharides (GOS) in the plant kingdom. Stellaria media is a typical representative of the Caryophyllaceae, a plant family lacking stachyose and the typical galactosyl extensions of stachyose. During cold treatment raffinose, lychnose (Gal-α(1 → 6)-Glc-α(1 → 2)β-Fru-α(1 → 1)-Gal) and stellariose (Gal-α(1 → 6)-[Gal-α(1 → 4)]-Glc-α(1 → 2)β-Fru-α(1 → 1)-Gal) were found to accumulate in S. media stems. Next to these prominent oligosaccharides, two extra GOS were discovered.Biochemical analyses (enzymatic incubations and mild acid hydrolysis) and mass spectrometry identified the first, most abundant oligosaccharide as Glc-α(1 → 2)β-Fru-α(1 → 1)-Gal, a breakdown product of lychnose. The structure of this trisaccharide was confirmed by full NMR characterization. The second, less abundant compound (termed mediose) was identified as Gal-α(1 → 6)-[Gal-α(1 → 4)]Glc-α(1 → 2)β-Fru after biochemical analyses. By partial enzyme purification the presence of discrete lychnose synthase (raffinose:raffinose 1^Fru galactosyltransferase) and stellariose synthase (raffinose:lychnose 4^Glc galactosyltransferase) activities were shown.A model is presented explaining the structural diversity of GOS in S. media. In the absence of stachyose, raffinose is further elongated by lychnose synthase and stellariose synthase to produce lychnose, mediose and stellariose. Most likely, these compounds are also subject to partial trimming by endogenous α-galactosidases.