Role of histone H3 lysine 27 methylation in X inactivation   总被引：1，自引：0，他引：1  

Plath K  Fang J  Mlynarczyk-Evans SK  Cao R  Worringer KA  Wang H  de la Cruz CC  Otte AP  Panning B  Zhang Y 《Science (New York, N.Y.)》2003,300(5616):131-135

The Polycomb group (PcG) protein Eed is implicated in regulation of imprinted X-chromosome inactivation in extraembryonic cells but not of random X inactivation in embryonic cells. The Drosophila homolog of the Eed-Ezh2 PcG protein complex achieves gene silencing through methylation of histone H3 on lysine 27 (H3-K27), which suggests a role for H3-K27 methylation in imprinted X inactivation. Here we demonstrate that transient recruitment of the Eed-Ezh2 complex to the inactive X chromosome (Xi) occurs during initiation of X inactivation in both extraembryonic and embryonic cells and is accompanied by H3-K27 methylation. Recruitment of the complex and methylation on the Xi depend on Xist RNA but are independent of its silencing function. Together, our results suggest a role for Eed-Ezh2-mediated H3-K27 methylation during initiation of both imprinted and random X inactivation and demonstrate that H3-K27 methylation is not sufficient for silencing of the Xi.  相似文献   

Rice false smut pathogen, Ustilaginoidea virens, invades through small gap at the apex of a rice spikelet before heading   总被引：1，自引：0，他引：1  

Taketo Ashizawa  Mami Takahashi  Michiyoshi Arai  Tsutomu Arie 《Journal of General Plant Pathology》2012,78(4):255-259

Ustilaginoidea virens, the false smut pathogen of rice, produces false smut balls on spikelets after heading. To clarify how the fungus invades spikelets during the booting stage, we developed a fungal strain that expresses a green fluorescent protein gene and injected conidia from this strain into rice sheaths. Observations at 48?h post-inoculation showed many conidia were present on spikelet surfaces, and the conidia had germinated and the hyphae have gradually grown by 120?h post-inoculation. By 144?h, hyphae had invaded spikelets through their apices, via the small gap between the lemma and palea and had already reached all floral organs.  相似文献   

The NS3 proteins of global strains of bluetongue virus evolve into regional topotypes through negative (purifying) selection   总被引：3，自引：0，他引：3  

Balasuriya UB  Nadler SA  Wilson WC  Pritchard LI  Smythe AB  Savini G  Monaco F  De Santis P  Zhang N  Tabachnick WJ  Maclachlan NJ 《Veterinary microbiology》2008,126(1-3):91-100

Comparison of the deduced amino acid sequences of the genes (S10) encoding the NS3 protein of 137 strains of bluetongue virus (BTV) from Africa, the Americas, Asia, Australia and the Mediterranean Basin showed limited variation. Common to all NS3 sequences were potential glycosylation sites at amino acid residues 63 and 150 and a cysteine at residue 137, whereas a cysteine at residue 181 was not conserved. The PPXY and PS/TAP late-domain motifs were conserved in all but three of the viruses. Phylogenetic analyses of these same sequences yielded two principal clades that grouped the viruses irrespective of their serotype or year of isolation (1900-2003). All viruses from Asia and Australia were grouped in one clade, whereas those from the other regions were present in both clades. Each clade segregated into distinct subclades that included viruses from single or multiple regions, and the S10 genes of some field viruses were identical to those of live-attenuated BTV vaccines. There was no evidence of positive selection on the S10 gene as assessed by reconstruction of ancestral codon states on the phylogeny, rather the functional constraints of the NS3 protein are expressed through substantial negative (purifying) selection.  相似文献   

Conformation Polymorphism of RNA Transcripts Derived from Various PNRSV Isolates is Affected by the Temperature of Electrophoresis     

Arie Rosner  Ludmila Maslenin  Sara Spiegel 《European journal of plant pathology / European Foundation for Plant Pathology》1999,105(4):413-415

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A putative RNA silencing component protein FoQde-2 is involved in virulence of the tomato wilt fungus <Emphasis Type="Italic">Fusarium oxysporum</Emphasis> f. sp. <Emphasis Type="Italic">lycopersici</Emphasis>     

Seong-Mi Jo  Yu Ayukawa  Sung-Hwan Yun  Ken Komatsu  Tsutomu Arie 《Journal of General Plant Pathology》2018,84(6):395-398

RNA silencing pathways in filamentous fungi are composed of multiple component proteins and known to be involved in vegetative growth, virulence or sexual reproduction. We found that the tomato wilt fungus, Fusarium oxysporum f. sp. lycopersici (Fol), carries four homologues genes of Qde-2, an argonaute protein gene and one of the main component protein genes in Neurospora crassa. Gene targeting revealed that FoQde-2, one of the Qde-2 homologues in Fol, is involved in virulence to tomato but not in vegetative growth.  相似文献   

Experimental evidence of a pathogenic change caused by homologous recombination between endogenous and introduced dysfunctional Avr-Pita genes in Pyricularia oryzae     

Takayuki Arazoe  Shigeru Kuwata  Tsutomu Arie  Shuichi Ohsato 《Journal of General Plant Pathology》2014,80(2):153-157

To provide experimental evidence that somatic homologous recombination (HR) is involved in the instability and diversification of the avirulence gene Avr-Pita in Pyricularia oryzae, we generated a dysfunctional Avr-Pita homolog and integrated it into strain Hoku-1 containing Avr-Pita. In the transformants, the occurrence of somatic HR events between Avr-Pita and the dysfunctional homolog was confirmed by PCR–RFLP. Germlings from conidia from the HR-positive transformants had lost the avirulence function, which enabled it to infect rice cultivar Yashiromochi containing the corresponding resistant gene Pi-ta. These results suggested that genetic mutation caused by somatic HR is one of the mechanisms responsible for virulence diversity.  相似文献   

Biological and phylogenetic characterization of Fusarium oxysporum complex, which causes yellows on Brassica spp., and proposal of F. oxysporum f. sp. rapae, a novel forma specialis pathogenic on B. rapa in Japan     

Enya J  Togawa M  Takeuchi T  Yoshida S  Tsushima S  Arie T  Sakai T 《Phytopathology》2008,98(4):475-483

Although the causal agent of yellows of Brassica rapa (turnip, pak choi, and narinosa) in Japan was reported in 1996 to be Fusarium oxysporum f. sp. conglutinans, this classification has remained inconclusive because of a lack of detailed genetic and pathogenic studies. Therefore, we analyzed the taxonomic position of this organism using Japanese isolates of F. oxysporum complex obtained from diseased individuals of various B. rapa subspecies. Phylogenetic analyses using partial sequences of the rDNA intergenic spacer region and the mating-type gene (MAT1-1-1alpha-box) showed that B. rapa and cabbage isolates belong to different monophyletic clades that separated at early evolutionary stages. Additionally, correlations were observed between the molecular phylogeny and the vegetative compatibility groups. Isolates from turnip, komatsuna, and narinosa (B. rapa group) did not show pathogenicity against cabbage or broccoli (B. oleracea group), although they caused severe symptoms on their original host species. In contrast, cabbage isolates had significantly higher (P = 0.05) virulence on B. oleracea than on B. rapa crops. Our results indicate that F. oxysporum complex isolates from B. rapa and B. oleracea are not only phylogenetically distinct but also differ in host specificity. Therefore, we propose a novel forma specialis, F. oxysporum f. sp. rapae, which causes yellows on B. rapa, including turnip, komatsuna, pak choi, and narinosa.  相似文献   

An avirulence gene homologue in the tomato wilt fungus Fusarium oxysporum f. sp. lycopersici race 1 functions as a virulence gene in the cabbage yellows fungus F. oxysporum f. sp. conglutinans     

Takeshi Kashiwa  Keigo Inami  Masashi Fujinaga  Hideki Ogiso  Takanobu Yoshida  Tohru Teraoka  Tsutomu Arie 《Journal of General Plant Pathology》2013,79(6):412-421

Six4, a small protein secreted by Fusarium oxysporum f. sp. lycopersici (Fol) in tomato xylem sap during infection, triggers Fol race 1-specific resistance (I) in tomato. SIX4 is regarded as an avirulence gene. Although SIX4 is considered unique to Fol race 1, we detected this gene in the cabbage yellows fungus F. oxysporum f. sp. conglutinans (Foc) by PCR. Because the genes from Foc and SIX4 in Fol were >99 % identical at the nucleotide level, the Foc gene was designated FocSIX4. The expression of FocSIX4 was detected by RT-PCR in stems and roots of cabbage 8 days after infection with Foc. In contrast with Fol, disruption of FocSIX4 in Foc did not increase virulence to Foc-resistant cabbage cvs. Shutoku-SP and Koikaze. On the contrary, the disruptants had reduced virulence not only on Foc-resistant cultivars but also on Foc-susceptible cv. Shikidori. These results suggested that FocSIX4 is involved in virulence, but not in avirulence, in the cabbage yellows fungus.  相似文献   

Construction of a system for exploring mitotic homologous recombination in the genome of Pyricularia oryzae     

Takayuki Arazoe  Shuichi Ohsato  Tsutomu Arie  Katsuyoshi Yoneyama  Shigeru Kuwata 《Journal of General Plant Pathology》2013,79(6):422-430

To investigate mitotic homologous recombination (HR) in Pyricularia oryzae, we created an HR detection system. The system consists of two non-functional enhanced yellow fluorescent protein (YFP) and blasticidin S deaminase (BSD) fusion genes (YFP::BSD). If mitotic HR occurs between the two non-functional genes in the genome, restoration of the functional YFP::BSD gene can be expected. The expression of the functional YFP::BSD gene can be detected by both YFP fluorescence and resistance against BS. When the P. oryzae genome was transformed simultaneously with two non-functional genes, all six lines of transformants with both genes had some portion of their hyphae exhibiting YFP fluorescence and BS resistance during growth. Up to ca. 10 % of conidia harvested from the mycelium of each of the six lines had YFP fluorescence, suggesting that HR consistently occurs during mycelium growth. To determine whether and how the HR-mediated phenotypic changes occurred at the DNA level, we analyzed the genomic DNA of BS-resistant mycelia by PCR-RFLP and sequencing and were able to confirm the existence of a restored functional YFP::BSD gene and a non-functional recombinant gene. Collectively, these findings demonstrate that we established a successful HR detection system for P. oryzae, which can be used for other plant pathogens, and that mitotic HR actually occurs in P. oryzae and constitute the first experimental evidence for mitotic HR in a fungus.  相似文献   

水分逆境下杨树光合作用的气孔与非气孔调控     

陈少良  王沙生 《中国林学(英文版)》1996,(2)

对杨树无性系：Ｉ－２１４（Ｐｏｐｕｌｕｓｅｕｒａｍｅｒｉｃａｎａｃｖ．Ｉ－２１４〕，健杨（Ｐ．ｅｕｒａｍｅｒｉｃａｎａＧｕｉｎｉｒｃｖ．Ｒｏｂｕｓｔａ），中东杨（Ｐ．ｂｅｒｏｌｉｎｅｎｓｉｓ）和群众杨（Ｐ．Ｐｏｐｕｌａｒｉｓ３５－４４）一年生盆栽插条苗进行干旱处理，研究了水分胁迫对四种苗木光合作用和叶绿素ａ荧光的影响．结果发现，苗木受旱后可变荧光提高２０－５０％，而恒定荧光未受水分胁迫的影响。鉴于光抑制是以可变荧光的降低为特征，因此得出光系统ＩＩ光反应中心未受伤害的结论。对土壤干旱敏感的Ｉ－２１４和健杨受旱后净光合作用（Ｐｎ）剧烈下降，主要是由于非气孔因素的影响：即ＲＵＢＰ羧化酶（Ｒｕｂｉｓｃｏ）的活性降低．耐旱性强的群众杨和中东杨，Ｐｎ下降的幅度较小，气孔因素和非气孔因素都是影响光合作用的因子。通过干旱或ＡＢＡ处理的叶片叶温升高，抑制了Ｒｕｂｉｓｃｏ的活性，也使叶绿素ａ荧光诱导曲线上的Ｍ峰消失，从而证实了Ｍ峰与光合作用暗反应的相关性。  相似文献