SummaryThe upregulation of the tryptophan (Trp) pathway in rice leaves infected by Bipolaris oryzae was indicated by: (i) enhanced enzyme activity of anthranilate synthase (AS), which regulates metabolic flux in the Trp pathway; (ii) elevated levels of the AS (OASA2, OASB1, and OASB2) transcripts; and (iii) increases in the contents of anthranilate, indole, and Trp. The measurement of the contents of Trp-derived metabolites by highperformance liquid chromatography coupled with tandem mass spectrometry revealed that serotonin and its hydroxycinnamic acid amides were accumulated in infected leaves. Serotonin accumulation was preceded by a transient increase in the tryptamine content and by marked activation of Trp decarboxylase, indicating that enhanced Trp production is linked to the formation of serotonin from Trp via tryptamine. Feeding of radiolabeled serotonin to inoculated leaves demonstrated that serotonin is incorporated into the cell walls of lesion tissue. The leaves of a propagating-type lesion mimic mutant (sl, Sekiguchi lesion) lacked both serotonin production and deposition of unextractable brown material at the infection sites, and showed increased susceptibility to B. oryzae infection. Treating the mutant with serotonin restored deposition of brown material at the lesion site. In addition, the serotonin treatment suppressed the growth of fungal hyphae in the leaf tissues of the sl mutant. These findings indicated that the activation of the Trp pathway is involved in the establishment of effective physical defenses by producing serotonin in rice leaves.

SummaryFungicides generally inhibit enzymatic reactions involved in fungal cellular biosynthesis. Here we report, for the first time, an example of fungicidal effects through hyperactivation of a fungal signal transduction pathway. The OSC1 gene, encoding a MAP kinase (MAPK) related to yeast Hog1, was isolated from the fungal pathogen Colletotrichum lagenarium that causes cucumber anthracnose. The osc1 knockout mutants were sensitive to high osmotic stress and showed increased resistance to the fungicide fludioxonil, indicating that Osc1 is involved in responses to hyperosmotic stress and sensitivity to fludioxonil. The Osc1 MAPK is phosphorylated under high osmotic conditions, indicating activation of Osc1 by high osmotic stress. Importantly, fludioxonil treatment also activates phosphorylation of Osc1, suggesting that improper activation of Osc1 by fludioxonil has negative effects on fungal growth. In the presence of fludioxonil, the wild-type fungus was not able to infect the host plant because of a failure of appressorium-mediated penetration, whereas osc1 mutants successfully infected plants. Analysis using a OSC1-GFP fusion gene indicated that Osc1 is rapidly translocated to the nucleus in appressorial cells after the addition of fludioxonil, suggesting that fludioxonil impairs the function of infection structures by activation of Osc1. Furthermore, fludioxonil activates Hog1-type MAPKs in the plant pathogenic fungi Cochliobolus heterostrophus and Botrytis cinerea . These results strongly suggest that fludioxonil acts as a fungicide, in part, through activation of the MAPK cascade in fungal pathogens.

Novel species of fungi described in this study include those from various countries as follows: Antarctica: Cadophora antarctica from soil. Australia: Alfaria dandenongensis on Cyperaceae, Amphosoma persooniae on Persoonia sp., Anungitea nullicana on Eucalyptus sp., Bagadiella eucalypti on Eucalyptus globulus, Castanediella eucalyptigena on Eucalyptus sp., Cercospora dianellicola on Dianella sp., Cladoriella kinglakensis on Eucalyptus regnans, Cladoriella xanthorrhoeae (incl. Cladoriellaceae fam. nov. and Cladoriellales ord. nov.) on Xanthorrhoea sp., Cochlearomyces eucalypti (incl. Cochlearomyces gen. nov. and Cochlearomycetaceae fam. nov.) on Eucalyptus obliqua, Codinaea lambertiae on Lambertia formosa, Diaporthe obtusifoliae on Acacia obtusifolia, Didymella acaciae on Acacia melanoxylon, Dothidea eucalypti on Eucalyptus dalrympleana, Fitzroyomyces cyperi (incl. Fitzroyomyces gen. nov.) on Cyperaceae, Murramarangomyces corymbiae (incl. Murramarangomyces gen. nov., Murramarangomycetaceae fam. nov. and Murramarangomycetales ord. nov.) on Corymbia maculata, Neoanungitea eucalypti (incl. Neoanungitea gen. nov.) on Eucalyptus obliqua, Neoconiothyrium persooniae (incl. Neoconiothyrium gen. nov.) on Persoonia laurina subsp. laurina, Neocrinula lambertiae (incl. Neocrinulaceae fam. nov.) on Lambertia sp., Ochroconis podocarpi on Podocarpus grayae, Paraphysalospora eucalypti (incl. Paraphysalospora gen. nov.) on Eucalyptus sieberi, Pararamichloridium livistonae (incl. Pararamichloridium gen. nov., Pararamichloridiaceae fam. nov. and Pararamichloridiales ord. nov.) on Livistona sp., Pestalotiopsis dianellae on Dianella sp., Phaeosphaeria gahniae on Gahnia aspera, Phlogicylindrium tereticornis on Eucalyptus tereticornis, Pleopassalora acaciae on Acacia obliquinervia, Pseudodactylaria xanthorrhoeae (incl. Pseudodactylaria gen. nov., Pseudodactylariaceae fam. nov. and Pseudodactylariales ord. nov.) on Xanthorrhoea sp., Pseudosporidesmium lambertiae (incl. Pseudosporidesmiaceae fam. nov.) on Lambertia formosa, Saccharata acaciae on Acacia sp., Saccharata epacridis on Epacris sp., Saccharata hakeigena on Hakea sericea, Seiridium persooniae on Persoonia sp., Semifissispora tooloomensis on Eucalyptus dunnii, Stagonospora lomandrae on Lomandra longifolia, Stagonospora victoriana on Poaceae, Subramaniomyces podocarpi on Podocarpus elatus, Sympoventuria melaleucae on Melaleuca sp., Sympoventuria regnans on Eucalyptus regnans, Trichomerium eucalypti on Eucalyptus tereticornis, Vermiculariopsiella eucalypticola on Eucalyptus dalrympleana, Verrucoconiothyrium acaciae on Acacia falciformis, Xenopassalora petrophiles (incl. Xenopassalora gen. nov.) on Petrophile sp., Zasmidium dasypogonis on Dasypogon sp., Zasmidium gahniicola on Gahnia sieberiana. Brazil: Achaetomium lippiae on Lippia gracilis, Cyathus isometricus on decaying wood, Geastrum caririense on soil, Lycoperdon demoulinii (incl. Lycoperdon subg. Arenicola) on soil, Megatomentella cristata (incl. Megatomentella gen. nov.) on unidentified plant, Mutinus verrucosus on soil, Par...

NDRG1 is an intracellular protein that is induced under a number of stress and pathological conditions, and it is thought to be associated with cell growth and differentiation. Recently, human NDRG1 was identified as a gene responsible for hereditary motor and sensory neuropathy-Lom (classified as Charcot-Marie-Tooth disease type 4D), which is characterized by early-onset peripheral neuropathy, leading to severe disability in adulthood. In this study, we generated mice lacking Ndrg1 to analyze its function and elucidate the pathogenesis of Charcot-Marie-Tooth disease type 4D. Histological analysis showed that the sciatic nerve of Ndrg1-deficient mice degenerated with demyelination at about 5 weeks of age. However, myelination of Schwann cells in the sciatic nerve was normal for 2 weeks after birth. Ndrg1-deficient mice showed muscle weakness, especially in the hind limbs, but complicated motor skills were retained. In wild-type mice, NDRG1 was abundantly expressed in the cytoplasm of Schwann cells rather than the myelin sheath. These results indicate that NDRG1 deficiency leads to Schwann cell dysfunction, suggesting that NDRG1 is essential for maintenance of the myelin sheaths in peripheral nerves. These mice will be used for future analyses of the mechanisms of myelin maintenance.NDRG1, an intracellular protein composed of 394 amino acids, is highly conserved among multicellular organisms, and its expression is induced by stress stimuli. Previously, we showed that NDRG1 is induced by homocysteine, 2-mercaptoethanol, and tunicamycin in cultured human endothelial cells (13). This pattern is similar to that seen for molecular chaperones in the endoplasmic reticulum. Subsequently, NDRG1 was found to be upregulated in a human lung cells following treatment with nickel compounds (31). This change in expression reflected an increase in hypoxia-inducible factor 1 caused by hypoxia or the subsequent elevation of intercellular calcium concentrations (23,24). NDRG1 expression is also induced by p53 expression and DNA damage, and its expression is inhibited under conditions of cell growth (14). These results suggest that NDRG1 is involved in the cellular stress response mechanisms.Conversely, Ndrg1 was also identified as a downstream target of N-myc (25). In N-myc knockout mouse embryos, NDRG1 expression is upregulated. During the early stages of differentiation of some tissues, it seems that N-myc activity leads to decreased NDRG1 expression as tissue differentiation progresses. Indeed, NDRG1 has been identified as a gene whose expression is downregulated in tumors (14, 27). Furthermore, NDRG1 expression is induced by differentiation stimuli in cancer cells (21,29). NDRG1 was also reported to be a metastasis suppressor gene (3, 6). In this regard, the effects of NDRG1 are thought to reflect its potential role in cell differentiation.Recently, a nonsense mutation of human NDRG1 was reported to be causative for hereditary motor and sensory neuropathy-Lom (9), which is a severe peripheral neuropathy identified in the Gypsy ...

Hydroxycinnamic acid amides (HCAAs) are secondary metabolites involved in the defense of plants against pathogens. Here, we report the first identification of HCAAs, p-coumaroylagmatine, feruloylagmatine, p-coumaroylputrescine and feruloylputrescine, in Arabidopsis thaliana rosette leaves infected with Alternaria brassicicola and the assignment of At5g61160 as the agmatine coumaroyltransferase (AtACT) that catalyzes the last reaction in the biosynthesis of the HCAAs. Feeding experiments with putative labeled precursors revealed that the four HCAAs were synthesized from hydroxycinnamic acids and agmatine or putrescine. AtACT gene function was identified from an analysis of a mutant that did not accumulate HCAAs. In wild-type Arabidopsis, AtACT transcripts markedly increased in response to A. brassicicola infection. Enzymatic activity that catalyzes the synthesis of the HCAAs was confirmed in vitro by using a recombinant AtACT expressed in Escherichia coli. The Atact mutant was susceptible to infection by A. brassicicola, indicating that HCAAs are responsible for defense against pathogens in A. thaliana.