Cloning and Characterization of the <Emphasis Type="Italic">BLR2</Emphasis>, the Homologue of the Blue-Light Regulator of <Emphasis Type="Italic">Neurospora crassa</Emphasis> WC-2, in the Phytopathogenic Fungus <Emphasis Type="Italic">Bipolaris oryzae</Emphasis>

Bipolaris oryzae is a filamentous ascomycetous fungus that causes brown leaf spot disease in rice. We isolated and characterized BLR2, a gene that encodes a putative blue-light regulator similar to Neurospora crassa white collar-2 (WC-2). The deduced amino acid sequence of the BLR2 showed significant homology to other fungal blue-light regulator proteins in the Per-Arnt-Sim (PAS) protein–protein interaction domain, nuclear localization signal, and GATA zinc finger DNA-binding domains. The BLR2-silenced transformants hardly produced conidia in the subsequent dark condition after near-ultraviolet (NUV) irradiation. Furthermore, the BLR2-silenced transformants suppressed the photolyase (PHR1) gene expression enhanced by NUV irradiation. These results indicate that BLR2 is necessary not only for conidial formation, but also for NUV radiation-enhanced photolyase gene expression in B. oryzae. The DDBJ accession number for the sequence reported in this paper is AB282674.     

A new atypical short-chain dehydrogenase is required for interfungal combat and conidiation in Trichoderma guizhouense

Hypocrealean Trichoderma are the most extensively studied facultative mycoparasites against phytopathogenic fungi. Aerial hyphae of Trichoderma guizhouense can rapidly proliferate over Fusarium oxysporum hyphae, cause sporadic cell death and arrest the growth of the host. The results of the present study demonstrated that a unique short-chain dehydrogenase/reductase (SDR), designated as TgSDR1, was expressed at a high level in T. guizhouense challenged by the hosts. Similar to other SDRs family members, the TgSDR1 protein contains a cofactor-binding motif and a catalytic site. The subcellular localization assay revealed that the TgSDR1::GFP fusion protein translocated to lipid droplets in mycelia and conidia. The data obtained using reverse genetic approach indicated that TgSDR1 is associated with antifungal ability, plays an important role in providing reducing equivalents in the form of NADPH and regulates the amino sugar and nucleotide sugar metabolism in T. guizhouense upon encountering a host. Moreover, the TgSDR1 deletion mutant was defective in conidiation. Thus, TgSDR1 functions as a key metabolic enzyme in T. guizhouense to regulate mycotrophic interactions, defence against other fungi, such as F. oxysporum, and conidiation.     

Cryptochrome photoreceptors cry1 and cry2 antagonistically regulate primary root elongation in Arabidopsis thaliana

Cryptochromes are blue-light receptors controlling multiple aspects of plant growth and development. They are flavoproteins with significant homology to photolyases, but instead of repairing DNA they function by transducing blue light energy into a signal that can be recognized by the cellular signaling machinery. Here we report the effect of cry1 and cry2 blue light receptors on primary root growth in Arabidopsis thaliana seedlings, through analysis of both cryptochrome-mutant and cryptochrome-overexpressing lines. Cry1 mutant seedlings show reduced root elongation in blue light while overexpressing seedlings show significantly increased elongation as compared to wild type controls. By contrast, the cry2 mutation has the opposite effect on root elongation growth as does cry1, demonstrating that cry1 and cry2 act antagonistically in this response pathway. The site of cryptochrome signal perception is within the shoot, and the inhibitor of auxin transport, 1-N-naphthylphthalamic acid, abolishes the differential effect of cryptochromes on root growth, suggesting the blue-light signal is transmitted from the shoot to the root by a mechanism that involves auxin. Primary root elongation in blue light may thereby involve interaction between cryptochrome and auxin signaling pathways.     

Isolation of <Emphasis Type="Italic">madA</Emphasis> homologs in <Emphasis Type="Italic">Pilobolus crystallinus</Emphasis>

Pilobolus crystallinus shows unique photoresponses at various growing stages. cDNAs for putative photoreceptors were cloned from this fungus. Three genes named pcmada1, pcmada2, and pcmada3 were identified from the PCR fragments, and amplified with degenerated primers for the LOV domain, which is conserved in many blue-light receptors. Deduced amino acid sequences for PCMADA1, PCMADA2, and PCMADA3 had one light-oxygen-voltage (LOV)-sensing and two PER-ARNT-SIM (PAS) domains. A zinc finger DNA-binding motif was conserved in the C-terminals of PCMADA1 and PCMADA3. However, PCMADA2 lacked the zinc finger motif. Expression of pcmada1 was suppressed by blue light whereas that of pcmada3 was promoted by blue-light irradiation.     

Genome-wide analyses of light-regulated genes in Aspergillus nidulans reveal a complex interplay between different photoreceptors and novel photoreceptor functions

Fungi sense light of different wavelengths using blue-, green-, and red-light photoreceptors. Blue light sensing requires the “white-collar” proteins with flavin as chromophore, and red light is sensed through phytochrome. Here we analyzed genome-wide gene expression changes caused by short-term, low-light intensity illumination with blue-, red- or far-red light in Aspergillus nidulans and found that more than 1100 genes were differentially regulated. The largest number of up- and downregulated genes depended on the phytochrome FphA and the attached HOG pathway. FphA and the white-collar orthologue LreA fulfill activating but also repressing functions under all light conditions and both appear to have roles in the dark. Additionally, we found about 100 genes, which are red-light induced in the absence of phytochrome, suggesting alternative red-light sensing systems. We also found blue-light induced genes in the absence of the blue-light receptor LreA. We present evidence that cryptochrome may be part of this regulatory cue, but that phytochrome is essential for the response. In addition to in vivo data showing that FphA is involved in blue-light sensing, we performed spectroscopy of purified phytochrome and show that it responds indeed to blue light.     

Identification of salt-tolerant gene HOG1 in Torulopsis versatilis

To understand the osmo-adaptation mechanism in Torulopsis versatilis (T), we investigated the salt-tolerant gene HOG1 from the wild-type and a salt-tolerant mutant strain (T5) constructed using genome shuffling. The HOG1 genes from T and T5 were sequenced and revealed several mutations had occurred. The expression level of T5HOG1 was stronger than that of THOG1, indicating a reason for the increase of salt-tolerance in T. versatilis. Moreover, overexpression of T5HOG1 and THOG1 improved the tolerance of salt in Saccharomyces cerevisiae. Identification and overexpression of THOG1 and T5HOG1 from the wild-type T. versatilis and the mutant T. versatilis, respectively, play an important role for the osmo-adaption mechanism of the T. versatilis used in soy-sauce fermentation.     

Light-induced absorbance changes in Phycomyces: evidence for cryptochrome-associated flavosemiquinones

Light-induced absorbance changes (LIACs), which are associated with early photochemical events of blue-light transduction, were detected in growing zones of Phycomyces sporangiophores. The novel LIACs meet all the essential requirements for a spectrophotometric photoreceptor assay which was previously unavailaible for blue-light receptors (cryptochromes). In-vivo absorption spectra of growing zones were derived from reflection spectra which were measured with a novel rapid-scan spectrophotometer. To detect photoreceptor-associated absorbance changes white mutants were employed which lack the interfering bulk pigment β-carotene. Blue and white light, not however red light, induced in these strains absorbance changes near 460–490 and 600–620 nm. The LIACs were absent in light-insensitive mutants with defects in the genes madA, madB and madC. Because these genes affect photosensory adaptation and the blue-light receptor itself, the novel in-vivo LIACs must be associated with photochemical events which occur early in the transduction chain. The spectral characteristics of the LIACs are in accordance with a blue- and red-light absorbing flavosemiquinone which is generated upon light absorption by an oxidized flavin receptor. It is proposed that the flavosemiquinone functions itself as photoreceptor which mediates several red-light responses of Phycomyces. Received: 28 September 1998 / Accepted: 25 November 1998     

fhy1 defines a branch point in phytochrome A signal transduction pathways for gene expression

Physiological analysis of the fhy1 mutant of Arabidopsis has led to the proposal that the mutant is deficient in a downstream component of the phytochrome A signal transduction pathway. To define this lesion at the molecular level, we have examined the expression of a range of phytochrome-regulated genes in fhy1. In far-red light, the regulation of genes such as CHS and CHI is blocked in fhy1, whereas the induction of CAB and NR genes is affected minimally. In contrast, the induction of all genes tested is blocked in a phytochrome A-deficient mutant, confirming that gene expression in far-red light is regulated solely by phytochrome A. Thus, fhy1 defines a branch point in phytochrome A signal transduction pathways for gene expression. Contrary to the general opinion that responses to continuous red light are mediated by phytochrome B and other photostable phytochromes, we have shown also that red light-induction of CHS is mediated almost entirely by phytochrome A. Furthermore, phytochrome A-mediated induction of CHS by red light is blocked in fhy1. The induction of CHS by blue light, however, is normal in fhy1, suggesting that although FHY1 is a component of the phytochrome A signaling pathway, it is not a component of the blue-light signaling pathway for CHS expression.     

Inhibition of germination of dormant barley (Hordeum vulgare L.) grains by blue light as related to oxygen and hormonal regulation

Germination of primary dormant barley grains is promoted by darkness and temperatures below 20 °C, but is strongly inhibited by blue light. Exposure under blue light at 10 °C for periods longer than five days, results in a progressive inability to germinate in the dark, considered as secondary dormancy. We demonstrate that the inhibitory effect of blue light is reinforced in hypoxia. The inhibitory effect of blue light is associated with an increase in embryo abscisic acid (ABA) content (by 3.5‐ to 3.8‐fold) and embryo sensitivity to both ABA and hypoxia. Analysis of expression of ABA metabolism genes shows that increase in ABA mainly results in a strong increase in HvNCED1 and HvNCED2 expression, and a slight decrease in HvABA8′OH‐1. Among the gibberellins (GA) metabolism genes examined, blue light decreases the expression of HvGA3ox2, involved in GA synthesis, increases that of GA2ox3 and GA2ox5, involved in GA catabolism, and reduces the GA signalling evaluated by the HvExpA11 expression. Expression of secondary dormancy is associated with maintenance of high embryo ABA content and a low HvExpA11 expression. The partial reversion of the inhibitory effect of blue light by green light also suggests that cryptochrome might be involved in this hormonal regulation.     

Acclimation of Arabidopsis thaliana to the light environment: regulation of chloroplast composition

The regulation by light of the composition of the photosynthetic apparatus was investigated in Arabidopsis thaliana (L.) Heynh. cv. Landsberg erecta. When grown in high- and low-irradiance white light, wild-type plants and photomorphogenic mutants showed large differences in their maximum photosynthetic rate and chlorophyll a/b ratios; such changes were abolished by growth in red light. Photosystem I (PSI) and PSII levels were measured in wild-type plants grown under a range of light environments; the results indicate that regulation of photosystem stoichiometry involves the specific detection of blue light. Supplementing red growth lights with low levels of blue light led to large increases in PSII content, while further increases in blue irradiance had the opposite effect; this latter response was abolished by the hy4 mutation, which affects certain events controlled by a blue-light receptor. Mutants defective in the phytochrome photoreceptors retained regulation of photosystem stoichiometry. We discuss the results in terms of two separate responses controlled by blue-light receptors: a blue-high-fluence response which controls photosystem stoichiometry; and a blue-low-fluence response necessary for activation of such control. Variation in the irradiance of the red growth light revealed that the blue-high-fluence response is attenuated by red light; this may be evidence that photosystem stoichiometry is controlled not only by photoreceptors, but also by photosynthetic metabolism.Abbreviations BHF blue-high-fluence - BLF blue-low-fluence - Chl chlorophyll - FR far-red light - LHCII light-harvesting complex of PSII - P_max maximum photosynthetic rate - R red light - Rubisco ribulose-1,5-bisphosphate carboxylase/oxygenase This work was supported by Natural Environment Research Council Grant No. GR3/7571A. We would like to thank H. Smith (Botany Department, University of Leicester) and E. Murchie (INRA, Versailles) for helpful discussions.     

2型猪链球菌脑膜炎小鼠模型的构建及其转录组学分析

【背景】2型猪链球菌(Streptococcus suis serotype 2, S. suis 2)可感染宿主引起严重的脑膜炎,对养猪业和人类公共卫生安全构成重大威胁。【目的】构建S. suis 2感染小鼠脑膜炎模型,并对其脑组织进行转录组学分析,为揭示S.suis2感染宿主后引起脑膜炎的分子机制和发现潜在的治疗靶点提供理论依据。【方法】采用S. suis 2感染小鼠,并对其脑组织进行病理组织学分析确认构建脑膜炎小鼠后,对其脑组织进行转录组学分析,对比S.suis2感染和未感染小鼠的差异表达基因,并对差异表达基因进行基因本体论(geneontology,GO)功能、京都基因和基因组百科全书(Kyoto encyclopedia of genes and genomes, KEGG)通路富集和韦恩分析。【结果】脑病理组织学分析结果显示,S. suis 2感染的小鼠脑膜中有大量的炎症细胞浸润,并且血管周围出现“袖套”现象,并能从感染小鼠的组织器官中再分离出攻毒的S. suis 2菌株,结果证明构建了S. suis 2感染脑膜炎小鼠模型。转录组学分析结果表明,感染S.suis2与未感染的...