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排序方式: 共有192条查询结果,搜索用时 31 毫秒
161.
A Brassica S-locus gene promoter targets toxic gene expression and cell death to the pistil and pollen of transgenic Nicotiana 总被引:14,自引:0,他引:14
The S-locus glycoprotein gene of Brassica is derived from the genetic locus that controls the self-incompatibility response and the specific recognition between pollen and stigma. The promoter of this gene was used to direct expression of the diphtheria toxin A chain gene and the Escherichia coli beta-glucuronidase gene in transgenic Nicotiana tabacum. Expression of the promoter in cells of the pistil and in pollen suggests that a single gene may direct the self-incompatibility response in the two interacting cell types. Additionally, the fusion genes were expressed gametophytically in the heterologous host species, Nicotiana, rather than sporophytically as expected for Brassica. Thus, although the genes involved in self-incompatibility in Brassica and Nicotiana are not homologous in their coding regions, signals for expression of these genes are apparently conserved between the two genera. Our analysis of toxic gene fusion transformants shows that genetic ablation is useful for probing developmental processes and for studying temporal and spatial patterns of gene expression in plants. 相似文献
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163.
Ablation of Papillar Cell Function in Brassica Flowers Results in the Loss of Stigma Receptivity to Pollination 总被引:14,自引:8,他引:6
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Kandasamy MK Thorsness MK Rundle SJ Goldberg ML Nasrallah JB Nasrallah ME 《The Plant cell》1993,5(3):263-275
Plant reproduction in crucifers is dependent on interactions that occur at the stigma surface between the male gametophyte (pollen and pollen tube) and papillar cells. To dissect these complex interactions, papillar cells were genetically ablated by targeting the expression of a toxin to appropriate cells of the flower with a flower-specific and developmentally regulated promoter. In transgenic Brassica plants that expressed the toxic gene fusion, flower morphology was normal except for aberrant papillar cell development and partial pollen sterility. Microscopic, biochemical, and functional analyses, mainly focused on papillar cell responses, revealed that papillar cells lost their ability to elongate, to synthesize cell-specific proteins, and to support pollen germination after self- or cross-pollination. This loss of stigma receptivity to pollination was mimicked by treating pistils with protein phosphatase inhibitors. Differences in the effects of genetic and chemical ablation on the pollination responses of Brassica and Arabidopsis flowers are discussed and are ascribed in part to a requirement for phosphorylation/dephosphorylation events in Brassica but not in Arabidopsis. 相似文献
164.
A phylogenetic survey using the polymerase chain reaction (PCR) has
identified four major P element subfamilies in the saltans and willistoni
species groups of Drosophila. One subfamily, containing about half of the
sequences studied, consists of elements that are very similar to the
canonical (and active) P element from D. melanogaster. Within this
subfamily, nucleotide sequence differentiation among different copies from
the same species and among elements from different species is relatively
low. This observation suggests that the canonical elements are relatively
recent additions to the genome or, less likely, are evolving slowly
relative to the other subfamilies. Elements belonging to the three
noncanonical lineages are distinct from the canonical elements and from one
another. Furthermore, there is considerably more sequence variation, on the
average, within the noncanonical subfamilies compared to the canonical
elements. Horizontal transfer and the coexistence of multiple,
independently evolving element subfamilies in the same genome may explain
the distribution of P elements in the saltans and willistoni species
groups. Such explanations are not mutually exclusive, and each may be
involved to varying degrees in the maintenance of P elements in natural
populations of Drosophila.
相似文献
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Casselman AL Vrebalov J Conner JA Singhal A Giovannoni J Nasrallah ME Nasrallah JB 《The Plant cell》2000,12(1):23-34
A genetic analysis was performed to study the frequency of recombination for intervals across the Brassica S locus region. No recombination was observed between the S locus glycoprotein gene and the S receptor kinase gene in the segregating populations that we analyzed. However, a number of recombination breakpoints in regions flanking these genes were identified, allowing the construction of an integrated genetic and physical map of the genomic region encompassing one S haplotype. We identified, based on the pollination phenotype of plants homozygous for recombinant S haplotypes, a 50-kb region that encompasses all specificity functions in the S haplotype that we analyzed. Mechanisms that might operate to preserve the tight linkage of self-incompatibility specificity genes within the S locus complex are discussed in light of the relatively uniform recombination frequencies that we observed across the S locus region and of the structural heteromorphisms that characterize different S haplotypes. 相似文献
168.
Evolution of interspecies unilateral incompatibility in the relatives of Arabidopsis thaliana
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Ling Li Bo Liu Xiaomei Deng Hainan Zhao Hongyan Li Shilai Xing Della D. Fetzer Mengya Li Mikhail E. Nasrallah June B. Nasrallah Pei Liu 《Molecular ecology》2018,27(12):2742-2753
The evolutionary concurrence of intraspecies self‐incompatibility (SI) and explosive angiosperm radiation in the Cretaceous have led to the hypothesis that SI was one of the predominant drivers of rapid speciation in angiosperms. Interspecies unilateral incompatibility (UI) usually occurs when pollen from a self‐compatible (SC) species is rejected by the pistils of a SI species, while the reciprocal pollination is compatible (UC). Although this SI × SC type UI is most prevalent and viewed as a prezygotic isolation barrier to promote incipient speciation of angiosperms, comparative evidence to support such a role is lacking. We show that SI × SI type UI in SI species pairs is also common in the well‐characterized accessions representing the four major lineages of the Arabidopsis genus and is developmentally regulated. This allowed us to reveal a strong correlation between UI strength and species divergence in these representative accessions. In addition, analyses of a SC accession and the pseudo‐self‐compatible (psc) spontaneous mutant of Arabidopsis lyrata indicate that UI shares, at least, common pollen rejection pathway with SI. Furthermore, genetic and genomic analyses of SI × SI type UI in A. lyrata × A. arenosa species pair showed that two major‐effect quantitative trait loci are the stigma and pollen‐side determinant of UI, respectively, which could be involved in heterospecies pollen discrimination. By revealing a close link between UI and SI pathway, particularly between UI and species divergence in these representative accessions, our findings establish a connection between SI and speciation. Thus, the pre‐existence of SI system would have facilitated the evolution of UI and accordingly promote speciation. 相似文献
169.
The permanently eutrophic Sundays Estuary experiences recurrent harmful algal blooms (HABs) of Heterosigma akashiwo (Raphidophyceae). This study aimed to identify the environmental variables shaping phytoplankton community composition and succession patterns during a typical spring/summer harmful algal bloom (HAB) period. Monitoring of abiotic and phytoplankton variables was undertaken over the period of a month in 2016. Surface water salinity corresponding to mesohaline conditions (9 to 12) was a prerequisite for site selection. During the study, two HABs (>550 µg Chl a l?1) of H. akashiwo occurred, each lasting for approximately a week in duration. Analyses highlighted nutrient depletion (i.e. nitrate and phosphate concentrations) as the key constraint on bloom duration. When the density of H. akashiwo decreased, the community composition became more diverse with species belonging to Bacillariophyceae and Dinophyceae becoming more abundant; albeit to a lesser degree (<180 µg Chl a l?1). Dissolved oxygen shifted from super-saturated conditions (>14 mg l?1) during peak HAB conditions, to instances of bottom water oxygen depletion (2–4 mg l?1) during the decay phase. These findings highlight the potential severity of transforming a catchment from natural to one that is highly regulated by agricultural practices, while also emphasising the need for management intervention. 相似文献
170.
Talita?FA?Ribas Luis?RR?Rodrigues Cleusa?Y?Nagamachi Anderson?JB?Gomes Thayse?CM?Benathar Patricia?CM?O’Brien Fengtang?Yang Malcolm?A?Ferguson-Smith Julio?C?PieczarkaEmail author 《BMC genetics》2013,14(1):119