Several wall-associated kinases participate positively and negatively in basal defense against rice blast fungus.

BACKGROUND: Receptor-like kinases are well-known to play key roles in disease resistance. Among them, the Wall-associated kinases (WAKs) have been shown to be positive regulators of fungal disease resistance in several plant species. WAK genes are often transcriptionally regulated during infection but the pathways involved in this regulation are not known. In rice, the OsWAK gene family is significantly amplified compared to Arabidopsis. The possibility that several WAKs participate in different ways to basal defense has not been addressed. Moreover, the direct requirement of rice OSWAK genes in regulating defense has not been explored. RESULTS: Here we show using rice (Oryza sativa) loss-of-function mutants of four selected OsWAK genes, that individual OsWAKs are required for quantitative resistance to the rice blast fungus, Magnaporthe oryzae. While OsWAK14, OsWAK91 and OsWAK92 positively regulate quantitative resistance, OsWAK112d is a negative regulator of blast resistance. In addition, we show that the very early transcriptional regulation of the rice OsWAK genes is triggered by chitin and is partially under the control of the chitin receptor CEBiP. Finally, we show that OsWAK91 is required for H2O2 production and sufficient to enhance defense gene expression during infection. CONCLUSIONS: We conclude that the rice OsWAK genes studied are part of basal defense response, potentially mediated by chitin from fungal cell walls. This work also shows that some OsWAKs, like OsWAK112d, may act as negative regulators of disease resistance

XLF and APLF bind Ku80 at two remote sites to ensure DNA repair by non-homologous end joining

International audienceThe Ku70-Ku80 (Ku) heterodimer binds rapidly and tightly to the ends of DNA double-strand breaks and recruits factors of the non-homologous end-joining (NHEJ) repair pathway through molecular interactions that remain unclear. We have determined crystal structures of the Ku-binding motifs (KBM) of the NHEJ proteins APLF (A-KBM) and XLF (X-KBM) bound to a Ku-DNA complex. The two KBM motifs bind remote sites of the Ku80 alpha/beta domain. The X-KBM occupies an internal pocket formed by an unprecedented large outward rotation of the Ku80 alpha/beta domain. We observe independent recruitment of the APLF-interacting protein XRCC4 and of XLF to laser-irradiated sites via binding of A- and X-KBMs, respectively, to Ku80. Finally, we show that mutation of the X-KBM and A-KBM binding sites in Ku80 compromises both the efficiency and accuracy of end joining and cellular radiosensitivity. A- and X-KBMs may represent two initial anchor points to build the intricate interaction network required for NHEJ

Role of Wall-Associated kinases and other regulators in rice resistance to the blast fungus Magnaporthe oryzae

La pyriculariose, maladie causée par le champignon phytopathogène Magnaporthe oryzae, affecte gravement le riz qui constitue l'aliment de base de plus de la moitié de la population mondiale. La connaissance des mécanismes de résistance est nécessaire pour guider la sélection variétale. Au cours de ce travail, une synthèse de la littérature a permis de recenser plus de 60 gènes régulateurs du riz impliqués dans la résistance du riz à différents agents pathogènes. Nous avons complété ces données en étudiant le rôle in planta de huit de ces régulateurs. Un rôle central du facteur de transcription OsWRKY28 a pu être établi et le rôle du récepteur CEBiP a été démontré. Ce travail a aussi exploré l'éventuelle implication d'une nouvelle famille de récepteurs, les Wall-Associated Kinases (WAK) dans la résistance chez le riz. Ce travail montre l'implication des WAK dans la résistance à M. oryzae. Alors que la transcription de la plupart de ces gènes est induite au cours de l'infection, celle du gène WAK112d est réprimée. La régulation transcriptionnelle précoce observée pour certains gènes WAK est déclenchée par la chitine et sous contrôle partiel du récepteur CEBiP et d'OsWRKY28. L'étude de mutants d'insertion et de lignées de surexpression a permis de montrer le rôle positif de trois gènes WAK et le rôle négatif du gène WAK112d dans la résistance. Des approches biochimiques seront nécessaires pour comprendre le mode de fonctionnement de ces récepteurs et pour les relier aux autres systèmes de défense connus.Rice blast disease, caused by the fungus Magnaporthe oryzae, is one of the most serious diseases on rice which is the staple food of more than the half of the world population. Improving our knowledge of resistance mechanisms is necessary to guide breeding programs. In this study, we reviewed over 60 rice gene regulators involved in resistance against various pathogens. We completed these data by analyzing the role of eight of these regulators. A pivotal role for the transcription factor OsWRKY28 has been established and the role of the CEBiP receptor in planta has been demonstrated. This work also shows the implication of some WAKs in rice blast resistance. Whereas the transcription of most of these genes is induced, transcription of the OsWAK112d gene is repressed upon infection. The early transcriptional regulation observed for some OsWAK genes is triggered by chitin and partially under CEBiP and OsWRKY28 regulation. Analysis of insertion mu tants and over-expressor lines revealed a positive role for three OsWAK genes and a negative role for OsWAK112d gene in rice blast resistance. Biochemical studies will be essential to understand how these receptors work and to connect them to other known defense systems

Role of Wall-Associated kinases and other regulators in rice resistance to the blast fungus Magnaporthe oryzae

La pyriculariose, maladie causée par le champignon phytopathogène Magnaporthe oryzae, affecte gravement le riz qui constitue l'aliment de base de plus de la moitié de la population mondiale. La connaissance des mécanismes de résistance est nécessaire pour guider la sélection variétale. Au cours de ce travail, une synthèse de la littérature a permis de recenser plus de 60 gènes régulateurs du riz impliqués dans la résistance du riz à différents agents pathogènes. Nous avons complété ces données en étudiant le rôle in planta de huit de ces régulateurs. Un rôle central du facteur de transcription OsWRKY28 a pu être établi et le rôle du récepteur CEBiP a été démontré. Ce travail a aussi exploré l'éventuelle implication d'une nouvelle famille de récepteurs, les Wall-Associated Kinases (WAK) dans la résistance chez le riz. Ce travail montre l'implication des WAK dans la résistance à M. oryzae. Alors que la transcription de la plupart de ces gènes est induite au cours de l'infection, celle du gène WAK112d est réprimée. La régulation transcriptionnelle précoce observée pour certains gènes WAK est déclenchée par la chitine et sous contrôle partiel du récepteur CEBiP et d'OsWRKY28. L'étude de mutants d'insertion et de lignées de surexpression a permis de montrer le rôle positif de trois gènes WAK et le rôle négatif du gène WAK112d dans la résistance. Des approches biochimiques seront nécessaires pour comprendre le mode de fonctionnement de ces récepteurs et pour les relier aux autres systèmes de défense connus.Rice blast disease, caused by the fungus Magnaporthe oryzae, is one of the most serious diseases on rice which is the staple food of more than the half of the world population. Improving our knowledge of resistance mechanisms is necessary to guide breeding programs. In this study, we reviewed over 60 rice gene regulators involved in resistance against various pathogens. We completed these data by analyzing the role of eight of these regulators. A pivotal role for the transcription factor OsWRKY28 has been established and the role of the CEBiP receptor in planta has been demonstrated. This work also shows the implication of some WAKs in rice blast resistance. Whereas the transcription of most of these genes is induced, transcription of the OsWAK112d gene is repressed upon infection. The early transcriptional regulation observed for some OsWAK genes is triggered by chitin and partially under CEBiP and OsWRKY28 regulation. Analysis of insertion mu tants and over-expressor lines revealed a positive role for three OsWAK genes and a negative role for OsWAK112d gene in rice blast resistance. Biochemical studies will be essential to understand how these receptors work and to connect them to other known defense systems.MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

WAKomics : large-scale functional analysis of the WAK genes involved in the rice Magnaporthe grisea interaction

International audienc

Potential candidate genes for improving Rice disease resistance

UMR BGPI Equipe 4iseases caused by fungal and bacterial pathogens like Magnaporthe oryzae and Xanthomonas oryzae pv. oryzae are responsible for considerable yield loss. Up to now, in rice, the modification of the expression of more than 60 genes from diverse origins has shown beneficial effects with respect to disease resistance. In this paper, we review this large set of data to identify the best genes and strategies to achieve disease resistance by transgenic approaches. Altered expression of genes involved in signal transduction and transcription may lead to many unwanted side effects, like lesion mimic phenotypes. Moreover, modification of resistance to abiotic stress has been neglected and should be carefully examined in the future. Genes like resistance genes and pathogenesis-related genes can confer broad spectrum and high levels of resistance to several pathogens. Preformed expression of defense is often observed but does not necessarily lead to detrimental effects. Although examples of gene pyramiding are scarce, they suggest that this is a very promising strategy. More field evaluation of the transgenic plants is required to draw final conclusions on the usefulness of these genes for improving disease resistance

Three wall-associated kinases required for rice basal immunity form protein complexes in the plasma membrane

BGPI : équipe 4International audienceReceptor-like kinases (RLKs) play key roles in disease resistance, in particular basal immunity. They recognize patterns produced by the pathogen invasion and often work as complexes in the plasma membrane. Among these RLKs, there is increasing evidence in several plant species of the key role of Wall-associated kinases (WAKs) in disease resistance. We recently showed using rice (Oryza sativa) loss-of-function mutants of three transcriptionaly co-regulated OsWAK genes that individual OsWAKs are positively required for quantitative resistance to the rice blast fungus, Magnaporthe oryzae. This finding was unexpected since WAK genes belong to large gene families where functional redundancy is expected. Here we provide evidence that this may be due to complex physical interaction between OsWAK proteins

Unravelling nutrient exchange in ectomycorrhizal symbiosis contributing to plant potassium nutrition

A major role of mutualistic interactions between plant roots and soil fungi is the improvement of plant nutrition by an equitable exchange of nutrients leading also to tolerance of environmental stress. Ectomycorrhizal symbiosis established between woody plants and soil fungi, widespread in forest ecosystems, is crucial for the plant partner to efficiently take up poorly available nutrients. Physiological studies as well as recent genome sequencing projects (Kohler et al. (2015) Nature Genet 47: 410-415) and transcriptome analyses (Doré et al. (2015) New Phytol 208: 1169-1187; Doré et al. (2017) Environ Microbiol 19:1338-1354) have allowed progress towards the identification and characterization of the symbiotic transportome (Garcia et al. (2016) Trends in Plant Science 21: 937-950). One of the major nutrients is potassium (K+ ), the most abundant cation in plant cells. We have shown improvement of potassium nutrition (Garcia et al. (2014) New Phytol 201: 951-960) under K+ shortage conditions by ectomycorrhizal symbiosis using two model species from European forests, Pinus pinaster and Hebeloma cylindrosporum. Questions are raised to identify the transport systems involved in the uptake of nutrients from the soil and in their transfer towards the plant at the symbiotic fungus-plant interface, called Hartig net. In the case of potassium (Garcia and Zimmermann (2014) Front Plant Sci 5: 337), we have identified two types of K+ transporters, Trk and HAK, as candidates to perform K+ uptake from the soil by the fungal extraradical hyphae, and two types of K+ channels, Shaker-like and TOK, that may release K+ by the hyphae of the Hartig net into the plant apoplasm. We have studied the three TOK (Two-pore Outward K+) channels identified in the genome of H. cylindrosporum, a channel family specific for fungi initially described in yeast (Ketchum et al. (1995) Nature 376: 690-695). These three TOK channels from the ectomycorrhizal fungus H. cylindrosporum belonging to two different subfamilies have been functionally characterized and localized (Carmen Guerrero-Galán et al. (2018) Env Microbiol , in press). Finally, we have analyzed whether these K+ channels might play specific roles within the fungus and within the symbiosis