Fire blight disease,caused by the bacterium Erwinia amylovora(E.amylovora),is responsible for substantial losses in cultivated apples worldwide.An important mechanism of plant immunity is based on the recognition of c...Fire blight disease,caused by the bacterium Erwinia amylovora(E.amylovora),is responsible for substantial losses in cultivated apples worldwide.An important mechanism of plant immunity is based on the recognition of conserved microbial molecules,named pathogen-associated or microbe-associated molecular patterns(PAMPs or MAMPs),through pattern recognition receptors(PRRs),leading to pattern-triggered immunity(PTI).The interspecies transfer of PRRs represents a promising strategy to engineer broad-spectrum and durable disease resistance in crops.EFR,the Arabidopsis thaliana PRR for the PAMP elf18 derived from the elongation factor thermal unstable(EF-Tu)proved to be effective in improving bacterial resistance when expressed into Solanaceae and other plant species.In this study,we tested whether EFR can affect the interaction of apple with E.amylovora by its ectopic expression in the susceptible apple rootstock M.26.Stable EFR expression led to the activation of PAMP-triggered immune response in apple leaves upon treatment with supernatant of E.amylovora,as measured by the production of reactive oxygen species and the induction of known defense genes.The amount of tissue necrosis associated with E.amylovora infection was significantly reduced in the EFR transgenic rootstock compared to the wild-type.Our results show that the expression of EFR in apple rootstock may be a valuable biotechnology strategy to improve the resistance of apple to fire blight.展开更多
Aims Functional traits are supposed to play an important role in deter-mining the colonization success of new species into established communities.short-term experimental studies have documented higher resistance of m...Aims Functional traits are supposed to play an important role in deter-mining the colonization success of new species into established communities.short-term experimental studies have documented higher resistance of more diverse grasslands against coloni-zation by new species.However,little is known about which traits colonizers should have to successfully invade diverse plant communities in the longer term and how community his-tory may modify the resistance of diverse communities against colonization.Methods In a grassland biodiversity experiment(Jena Experiment)established with different species richness(s;1,2,4,8 and 16)and functional group(Fg)number and composition(1 to 4;legumes,grasses,small herbs,tall herbs),we studied colonization of naturally dispersed species in split-plots(i)with different duration of weeding(never weeded,weeded for 3 or 6 years and then un-weeded for 1 year)and(ii)with different duration of colonization(7 years,4 years and 1 year after cessation of weeding).Important Findingsresistance against colonization by new species declined with increased duration of weeding(on average 13,17 and 22 col-onizer species in 1-,4-and 7-year-old communities,respec-tively).Communities established at low diversity accumulated more colonizer species with a longer duration of weeding than more diverse communities.Duration of colonization had only small effects on the number of colonizer species.Colonizers with early successional traits,i.e.annual life cycle,reproduction by seeds,small seeds,long-lived seeds and an earlier start of a longer flowering period,were favoured in species-poor newly established experimental plant communities(short duration of weeding)and early after cessation of weeding(short duration of colonization).a change from early-to mid-successional traits,i.e.taller growth,perennial life cycle,vegetative reproduction,characterized colonization at increased plant diversity and in communities with legumes or without grasses.legume absence/grass presence and increased duration of weeding led to a shift in colonizer strategies from rapid nutrient uptake and cycling(higher specific leaf area)to nutrient retention and symbiotic N2 fixation.our study shows that non-random trait spectra of naturally dispersed colonizers encompass trade-offs between different functions(reproduction,persistence,growth)reflected in a change from early-to mid-successional traits at increasing plant diversity,with a longer duration of weeding and a longer time of colonization.展开更多
Arabidopsis MSI1 has fundamental functions in plant development. MSI1 is a subunit of Polycomb group protein complexes and Chromatin assembly factor 1, and it interacts with the Retinoblastoma-related protein 1. Alter...Arabidopsis MSI1 has fundamental functions in plant development. MSI1 is a subunit of Polycomb group protein complexes and Chromatin assembly factor 1, and it interacts with the Retinoblastoma-related protein 1. Altered levels of MSI1 result in pleiotropic phenotypes, reflecting the complexity of MSI1 protein functions. In order to uncover additional functions of MSI1, we performed transcriptional profiling of wild-type and plants with highly reduced MSI1 levels （msil-cs）. Surprisingly, the known functions of MSI1 could only account for a minor part of the transcriptional changes in msil-cs plants. One of the most striking unexpected observations was the up-regulation of a subset of ABA-responsive genes eliciting the response to drought and salt stress. We report that MSI1 can bind to the chromatin of the drought-inducible downstream target RD20 and suggest a new role for MSI1 in the negative regulation of the Arabidopsis drought-stress response.展开更多
Genomic imprinting is an epigenetic phenomenon that causes monoallelic expression of specific genes dependent on the parent-of-origin. Imprinting of the Arabidopsis gene PHERES1 requires the function of the FERTILIZAT...Genomic imprinting is an epigenetic phenomenon that causes monoallelic expression of specific genes dependent on the parent-of-origin. Imprinting of the Arabidopsis gene PHERES1 requires the function of the FERTILIZATION INDEPENDENT SEED （FIS） Polycomb group complex as well as a distally located methylated region containing a tandem triple repeat sequence. In this study, we investigated the regulation of the close PHERES1 homolog PHERES2. We found that PHERES2 is also a direct target gene of the FIS Polycomb group complex, but, in contrast to PHERES1, PHERES2 is equally expressed from maternal and paternal alleles. Thus, PHERES2 is not regulated by genomic imprinting, correlating with the lack of tandem repeats at PHERES2. Eliminating tandem repeats from the PHERES1 locus abolishes PHERES1 imprinting, demonstrating that tandem repeats are essential forPHERES1 imprinting. Taking these results together, our study shows that the recently duplicated genes PHERES1 and PHERES2 are both target genes of the FIS Polycomb group complex but only PHERES1 is regulated by genomic imprinting, which is likely caused by the presence of repeat sequences in the proximity of the PHERES1 locus.展开更多
Calcium acts as a second messenger for signaling to a variety of stimuli including MAMPs （Microbe-Associated Molecular Patterns）, such as fig22 and elf18 that are derived from bacterial flagellin and elongation fact...Calcium acts as a second messenger for signaling to a variety of stimuli including MAMPs （Microbe-Associated Molecular Patterns）, such as fig22 and elf18 that are derived from bacterial flagellin and elongation factor Tu, respectively. Here, Arabidopsis thaliana mutants with changed calcium elevation （cce） in response to fig22 treatment were isolated and characterized. Besides novel mutant alleles of the fig22 receptor, FLS2 （Flagellin-Sensitive 2）, and the receptor-associated kinase, BAK1 （Brassinosteroid receptor 1-Associated Kinase 1）, the new cce mutants can be categorized into two main groups--those with a reduced or an enhanced calcium elevation. Moreover, cce mutants from both groups show differ- ential phenotypes to different sets of MAMPs. Thus, these mutants will facilitate the discovery of novel components in early MAMP signaling and bridge the gaps in current knowledge of calcium signaling during plant-microbe interactions. Last but not least, the screening method is optimized for speed （covering 384 plants in 3 or 10 h） and can be adapted to genetically dissect any other stimuli that induce a change in calcium levels.展开更多
Successful double fertilization and subsequent seed development in flowering plants requires the delivery of two sperm cells, transported by a pollen tube, into the embryo sac of an ovule. The embryo sac cells tightly...Successful double fertilization and subsequent seed development in flowering plants requires the delivery of two sperm cells, transported by a pollen tube, into the embryo sac of an ovule. The embryo sac cells tightly control synergid cell death, and as a result the polyspermy block. Arabinogalactan proteins are highly glycosylated proteins thought to be involved in several steps of the reproductive process. We show that JAGGER, Arabinogalactan Protein 4, is an important molecule necessary to prevent the growth of multiple pollen tubes into one embryo sac in Arabidopsis thaliana. In jagger, an AGP4 knockout mutant, the pistils show impaired pollen tube blockage as a consequence of the survival of the persistent synergid. JAGGER seems to be involved in the signaling pathway that leads to a blockage of pollen tube attraction. Our results shed light on the mechanism responsible for preventing polyspermy in Arabidopsis and for safe- guarding successful fertilization of all ovules in one pistil, ensuring seed set and the next generation.展开更多
基金This work was funded by the Autonomous Province of Trento.
文摘Fire blight disease,caused by the bacterium Erwinia amylovora(E.amylovora),is responsible for substantial losses in cultivated apples worldwide.An important mechanism of plant immunity is based on the recognition of conserved microbial molecules,named pathogen-associated or microbe-associated molecular patterns(PAMPs or MAMPs),through pattern recognition receptors(PRRs),leading to pattern-triggered immunity(PTI).The interspecies transfer of PRRs represents a promising strategy to engineer broad-spectrum and durable disease resistance in crops.EFR,the Arabidopsis thaliana PRR for the PAMP elf18 derived from the elongation factor thermal unstable(EF-Tu)proved to be effective in improving bacterial resistance when expressed into Solanaceae and other plant species.In this study,we tested whether EFR can affect the interaction of apple with E.amylovora by its ectopic expression in the susceptible apple rootstock M.26.Stable EFR expression led to the activation of PAMP-triggered immune response in apple leaves upon treatment with supernatant of E.amylovora,as measured by the production of reactive oxygen species and the induction of known defense genes.The amount of tissue necrosis associated with E.amylovora infection was significantly reduced in the EFR transgenic rootstock compared to the wild-type.Our results show that the expression of EFR in apple rootstock may be a valuable biotechnology strategy to improve the resistance of apple to fire blight.
基金Fund for Jena Experiment:German Science Foundation(FOR 456)additional support:Max Planck SocietyFriedrich Schiller University of Jena and coordinated by W.W.Weisser.
文摘Aims Functional traits are supposed to play an important role in deter-mining the colonization success of new species into established communities.short-term experimental studies have documented higher resistance of more diverse grasslands against coloni-zation by new species.However,little is known about which traits colonizers should have to successfully invade diverse plant communities in the longer term and how community his-tory may modify the resistance of diverse communities against colonization.Methods In a grassland biodiversity experiment(Jena Experiment)established with different species richness(s;1,2,4,8 and 16)and functional group(Fg)number and composition(1 to 4;legumes,grasses,small herbs,tall herbs),we studied colonization of naturally dispersed species in split-plots(i)with different duration of weeding(never weeded,weeded for 3 or 6 years and then un-weeded for 1 year)and(ii)with different duration of colonization(7 years,4 years and 1 year after cessation of weeding).Important Findingsresistance against colonization by new species declined with increased duration of weeding(on average 13,17 and 22 col-onizer species in 1-,4-and 7-year-old communities,respec-tively).Communities established at low diversity accumulated more colonizer species with a longer duration of weeding than more diverse communities.Duration of colonization had only small effects on the number of colonizer species.Colonizers with early successional traits,i.e.annual life cycle,reproduction by seeds,small seeds,long-lived seeds and an earlier start of a longer flowering period,were favoured in species-poor newly established experimental plant communities(short duration of weeding)and early after cessation of weeding(short duration of colonization).a change from early-to mid-successional traits,i.e.taller growth,perennial life cycle,vegetative reproduction,characterized colonization at increased plant diversity and in communities with legumes or without grasses.legume absence/grass presence and increased duration of weeding led to a shift in colonizer strategies from rapid nutrient uptake and cycling(higher specific leaf area)to nutrient retention and symbiotic N2 fixation.our study shows that non-random trait spectra of naturally dispersed colonizers encompass trade-offs between different functions(reproduction,persistence,growth)reflected in a change from early-to mid-successional traits at increasing plant diversity,with a longer duration of weeding and a longer time of colonization.
文摘Arabidopsis MSI1 has fundamental functions in plant development. MSI1 is a subunit of Polycomb group protein complexes and Chromatin assembly factor 1, and it interacts with the Retinoblastoma-related protein 1. Altered levels of MSI1 result in pleiotropic phenotypes, reflecting the complexity of MSI1 protein functions. In order to uncover additional functions of MSI1, we performed transcriptional profiling of wild-type and plants with highly reduced MSI1 levels （msil-cs）. Surprisingly, the known functions of MSI1 could only account for a minor part of the transcriptional changes in msil-cs plants. One of the most striking unexpected observations was the up-regulation of a subset of ABA-responsive genes eliciting the response to drought and salt stress. We report that MSI1 can bind to the chromatin of the drought-inducible downstream target RD20 and suggest a new role for MSI1 in the negative regulation of the Arabidopsis drought-stress response.
文摘Genomic imprinting is an epigenetic phenomenon that causes monoallelic expression of specific genes dependent on the parent-of-origin. Imprinting of the Arabidopsis gene PHERES1 requires the function of the FERTILIZATION INDEPENDENT SEED （FIS） Polycomb group complex as well as a distally located methylated region containing a tandem triple repeat sequence. In this study, we investigated the regulation of the close PHERES1 homolog PHERES2. We found that PHERES2 is also a direct target gene of the FIS Polycomb group complex, but, in contrast to PHERES1, PHERES2 is equally expressed from maternal and paternal alleles. Thus, PHERES2 is not regulated by genomic imprinting, correlating with the lack of tandem repeats at PHERES2. Eliminating tandem repeats from the PHERES1 locus abolishes PHERES1 imprinting, demonstrating that tandem repeats are essential forPHERES1 imprinting. Taking these results together, our study shows that the recently duplicated genes PHERES1 and PHERES2 are both target genes of the FIS Polycomb group complex but only PHERES1 is regulated by genomic imprinting, which is likely caused by the presence of repeat sequences in the proximity of the PHERES1 locus.
基金This work was supported by a Deutsche Forschungsgemeinschaft (DFG) grant，financed by the DFG grant，by the Swiss National Science Foundation grant
文摘Calcium acts as a second messenger for signaling to a variety of stimuli including MAMPs （Microbe-Associated Molecular Patterns）, such as fig22 and elf18 that are derived from bacterial flagellin and elongation factor Tu, respectively. Here, Arabidopsis thaliana mutants with changed calcium elevation （cce） in response to fig22 treatment were isolated and characterized. Besides novel mutant alleles of the fig22 receptor, FLS2 （Flagellin-Sensitive 2）, and the receptor-associated kinase, BAK1 （Brassinosteroid receptor 1-Associated Kinase 1）, the new cce mutants can be categorized into two main groups--those with a reduced or an enhanced calcium elevation. Moreover, cce mutants from both groups show differ- ential phenotypes to different sets of MAMPs. Thus, these mutants will facilitate the discovery of novel components in early MAMP signaling and bridge the gaps in current knowledge of calcium signaling during plant-microbe interactions. Last but not least, the screening method is optimized for speed （covering 384 plants in 3 or 10 h） and can be adapted to genetically dissect any other stimuli that induce a change in calcium levels.
文摘Successful double fertilization and subsequent seed development in flowering plants requires the delivery of two sperm cells, transported by a pollen tube, into the embryo sac of an ovule. The embryo sac cells tightly control synergid cell death, and as a result the polyspermy block. Arabinogalactan proteins are highly glycosylated proteins thought to be involved in several steps of the reproductive process. We show that JAGGER, Arabinogalactan Protein 4, is an important molecule necessary to prevent the growth of multiple pollen tubes into one embryo sac in Arabidopsis thaliana. In jagger, an AGP4 knockout mutant, the pistils show impaired pollen tube blockage as a consequence of the survival of the persistent synergid. JAGGER seems to be involved in the signaling pathway that leads to a blockage of pollen tube attraction. Our results shed light on the mechanism responsible for preventing polyspermy in Arabidopsis and for safe- guarding successful fertilization of all ovules in one pistil, ensuring seed set and the next generation.
