Changes of fatty acids and sterols in apple buds during bud break induced by a plant bioregulator, thidiazuron

The effects of N-phenyl-N'-l,2,3,-thidiazol-5-ylurea (thidiazuron; Dropp; SN 49537) on fatty acids of membrane lipids and sterol content in apple ( Malus domestica Borkh cv. Golden Delicious) buds associated with bud break and bud development were determined. The predominant fatty acids in the membrane lipids of apple buds were palmitic acid (C16:0), linoleic acid (C18:2) and linolenic acid (C18:3). β -Sitosterol and sitosteryl ester were the predominant sterols. An accumulation of unsaturated polar membrane fatty acids started after thidiazuron treatment. A decrease in the percentage of the sitosterol was accompanied by an increase in campesterol and stigmasterol at the beginning of rapid growth. An increase in the ratio of campesterol and stigmasterol to sitosterol and a decrease in the ratio of free sterols to membrane lipids upon breaking of dormancy also occurred in apple buds induced by thidiazuron.     

Reproductive biology and responses to threats and protection measures of the total population of a Critically Endangered Galápagos plant,Linum cratericola (Linaceae)

We describe a reproductive and population dynamic study of the total population of a Critically Endangered plant over 10 years, during which part of the population was protected from the main threat, feral ungulates. Linum cratericola (Linaceae) was first discovered in 1966 at two sites on Floreana Island, Galápagos. It has since disappeared from one site and survives in three groups of plants at the other, where it has been threatened with extinction by introduced ungulates and invasive plants. Population size, and growth rate and mortality of individual plants, have been monitored since 1997. The population appears highly responsive to changes in threat levels: the three plant groups increased rapidly following protection by fencing and ungulate control, but temporarily declined when feral goat pressure increased and during dry periods. Natural factors that may contribute to population limitation include dry years, grazing by native snails and competition from native vascular plants and cryptogams. Linum cratericola has a single flowering period per year and produces abundant seed with 28% germination after scarification, but with no obvious adaptations for long‐distance dispersal. Potential pollinators included the butterfly Leptotes parrhasioides, the hoverfly Toxomerus crockeri and the carpenter bee Xylocopa darwinii, all endemic to Galápagos. The continued survival of L. cratericola in the wild depends on effective protection from introduced herbivores and invasive plants. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 161 , 89–102.     

Oviposition strategy as a means of local adaptation to plant defence in native and invasive populations of the viburnum leaf beetle

Herbivores have been hypothesized to adapt locally to variation in plant defences and such adaptation could facilitate novel associations in the context of biological invasions. Here, we show that in the native range of the viburnum leaf beetle (VLB, Pyrrhalta viburni), two populations of geographically isolated hosts-Viburnum opulus and Viburnum tinus-have divergent defences against VLB oviposition: negative versus positive density-dependent egg-crushing wound responses, respectively. Populations of beetles coexisting with each host show an adaptive behavioural response: aggregative versus non-aggregative oviposition on V. opulus and V. tinus, respectively. In parallel, we show that in North America, where VLB is invasive, defences of three novel hosts are negatively density-dependent, and beetles' oviposition behaviour is aggregative. Thus, local adaptation to plant defences has the potential to facilitate the invasion of herbivores onto novel hosts.     

Evolution of genome size and chromosome number in the carnivorous plant genus Genlisea (Lentibulariaceae), with a new estimate of the minimum genome size in angiosperms

MethodsNuclear genome sizes were measured from cultivated plant material for a comprehensive sampling of taxa, including nearly half of all species of Genlisea and representing all major lineages. Flow cytometric measurements were conducted in parallel in two laboratories in order to compare the consistency of different methods and controls. Chromosome counts were performed for the majority of taxa, comparing different staining techniques for the ultrasmall chromosomes.ConclusionsGenlisea is an ideal candidate model organism for the understanding of genome reduction as the genus includes species with both relatively large (∼1700 Mbp) and ultrasmall (∼61 Mbp) genomes. This comparative, phylogeny-based analysis of genome sizes and karyotypes in Genlisea provides essential data for selection of suitable species for comparative whole-genome analyses, as well as for further studies on both the molecular and cytogenetic basis of genome reduction in plants.     

Integrating Bayesian genomic cline analyses and association mapping of morphological and ecological traits to dissect reproductive isolation and introgression in a Louisiana Iris hybrid zone

Hybrid zones provide unique opportunities to examine reproductive isolation and introgression in nature. We utilized 45,384 single nucleotide polymorphism (SNP) loci to perform association mapping of 14 floral, vegetative and ecological traits that differ between Iris hexagona and Iris fulva, and to investigate, using a Bayesian genomic cline (BGC) framework, patterns of genomic introgression in a large and phenotypically diverse hybrid zone in southern Louisiana. Many loci of small effect size were consistently found to be associated with phenotypic variation across all traits, and several individual loci were revealed to influence phenotypic variation across multiple traits. Patterns of genomic introgression were quite heterogeneous throughout the Louisiana Iris genome, with I. hexagona alleles tending to be favoured over those of I. fulva. Loci that were found to have exceptional patterns of introgression were also found to be significantly associated with phenotypic variation in a small number of morphological traits. However, this was the exception rather than the rule, as most loci that were associated with morphological trait variation were not significantly associated with excess ancestry. These findings provide insights into the complexity of the genomic architecture of phenotypic differences and are a first step towards identifying loci that are associated with both trait variation and reproductive isolation in nature.     

Flow cytometric analysis of the Th1-Th2 balance in healthy individuals and patients infected with the human immunodeficiency virus (HIV) receiving a plant sterol/sterolin mixture

The Th1--Th2 balance plays a pivotal role in determining the outcome of an immune response to an infectious organism. It is proposed that during HIV infection, disease progression is characterized by a loss of Th1 activity, a shift to a more 'allergic' Th2-type response and hence loss of cytotoxic cell activity against infected host cells. This study was undertaken to investigate this balance in three groups of individuals: HIV-negative volunteers (n=10), a group of HIV-infected patients on no therapy (n=10) as well as a group of patients managed with a mixture of plant sterols/sterolins (n=9). In parallel, their response to mitogens and the subsequent expression of the activation antigen CD69 was measured. This study was conducted by three-colour flow cytometry in order to obviate the less sensitive cytokine secretion assays that have yielded controversial results. The results indicate that HIV-infected patients on no therapy exhibit a pre-dominant Th2 response (IL-4 secretion), whereas those on the sterol/sterolin mixture exhibit a beneficial Th1 response (IFN-gamma). Surprisingly, in both patient groups, the expression of CD69 was abnormally low when compared to the uninfected volunteers, implying that chronic activation is already present in vivo. It appears that the detrimental Th2 driven response might be swung to the more beneficial Th1 response with the immune modulatory sterols/sterolin mixture. Clinical use of this mixture in HIV infection has yielded results which corroborate the above observations in that patients using the plant sterol/sterolin mixture maintain their CD4 cell numbers over an extended period of time in the absence of any anti-retroviral therapy.     

Selective support of a mouse thymus epithelial cell line （MTEC1） to the viability and proliferation of CD4＋CD8—,CD4^—CD8^—,and CD4^＋CD8^＋thymocytes in vitro

The MTEC1 cell line,established in our laboratory,is a normal epithelial cell line derived from thymus medulla of Balb/c mice and these cells constituteively produce multiple cytokines.The selection of thymic microenvironment on developing T cells was investigated in an in vitro system.Unseparated fresh thymocytes from Balb/c mice were cocultured with MTEC1 cells or/and MTEC1-SN,then,the viability,proliferation and phenotypes of cultured thymocytes were assessed.Without any exogenous stimulus,both MTEC1 cells and MTEC1-SN were able to maintain the viability of thymocytes,while only the MTEC1 cells,not the MTEC1-SN,could directly activate thymocytes to exhibit moderate proliferation,indicating that the proliferative signal is delivered through cell surface interatcions of MTEC1 cells and thymocytes.Phenotype analysis on FACS of viable thymocytes after coculture revealed that MTEC1 cells preferentially activate the subsets of CD4^ CD8^-,CD4^ CD^8 and CD^4- CD^8- thymocytes;whereas MTEC1-SN preferentially maintained the viability of CD4^ CD^8- and CD4^-CD8^ thymocyte subsets.For the Con A-activated thymocytes.both MTEC1 cells and MTEC1-SN provided accessory signal(s) to significantly increase the number of viable cells and to markedly enhance the proliferation of thymocytes with virtually equal potency,phenotyped as CD4^ CD8^-,CD4^-CD8^ ,and CD^4-CD8^-subests,In summary,MTEC1 cells displayed Selection of thymic epithelial cells on thymocyte subsets. selective support to the different thymocyte subsets,and the selectivity is dependent on the status of thymocytes.     

Temporal and host-related variation in frequencies of genes that enable Phyllotreta nemorum to utilize a novel host plant, Barbarea vulgaris

The flea beetle, Phyllotreta nemorum L. (Coleoptera: Chrysomelidae), is an intermediate specialist feeding on a small number of plants within the family Brassicaceae. The most commonly used host plant is Sinapis arvensis L., whereas the species is found more rarely on Cardaria draba (L.) Desv., Barbarea vulgaris R.Br., and cultivated radish (Raphanus sativus L.). The interaction between flea beetles and Barbarea vulgaris ssp. arcuata (Opiz.) Simkovics seems to offer a good opportunity for experimental studies of coevolution. The plant is polymorphic, as it contains one type (the P‐type) that is susceptible to all flea beetle genotypes, and another type (the G‐type) that is resistant to some genotypes. At the same time, the flea beetle is also polymorphic, as some genotypes can utilize the G‐type whereas others cannot. The ability to utilize the G‐type of B. vulgaris ssp. arcuata is controlled by major dominant genes (R‐genes). The present investigation measured the frequencies of flea beetles with R‐genes in populations living on different host plants in 2 years (1999 and 2003). Frequencies of beetles with R‐genes were high in populations living on the G‐type of B. vulgaris ssp. arcuata in both years. Frequencies of beetles with R‐genes were lower in populations living on other host plants, and declining frequencies were observed in five out of six populations living on S. arvensis. Selection in favour of R‐genes in populations living on B. vulgaris is the most likely mechanism to account for the observed differences in the relative abundance of R‐genes in flea beetle populations utilizing different host plants. A geographic mosaic with differential levels of interactions between flea beetles and their host plants was demonstrated.