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Extracellular vesicles (EVs) are important for cell-to-cell communication in animals. EVs also play important roles in plant–microbe interactions, but the underlying mechanisms remain elusive. Here, proteomic analyses of EVs from the soybean (Glycine max) root rot pathogen Phytophthora sojae identify the tetraspanin family proteins PsTET1 and PsTET3, which are recognized by Nicotiana benthamiana to trigger plant immune responses. Both proteins are required for the full virulence of P. sojae. The large extracellular loop (EC2) of PsTET3 is the key region recognized by N. benthamiana and soybean cells in a plant receptor-like kinase NbSERK3a/b dependent manner. TET proteins from oomycete and fungal plant pathogens are recognized by N. benthamiana thus inducing immune responses, whereas plant-derived TET proteins are not due to the sequence divergence of sixteen amino acids at the C-terminal of EC2. This feature allows plants to distinguish self and non-self EVs to trigger active defense responses against pathogenic eukaryotes. Extracellular vesicles (EVs) are important in plant-microbe interactions. Here we show that the divergent sequences within tetraspanins localized at EV membranes enable plant innate immune system to distinguish between self and non-self EVs. [ABSTRACT FROM AUTHOR]

Oomycetes are a group of filamentous microorganisms that include some of the biggest threats to food security and natural ecosystems. However, much of the molecular basis of the pathogenesis and the development in these organisms remains to be learned, largely due to shortage of efficient genetic manipulation methods. In this study, we developed modified transformation methods for two important oomycete species, Phytophthora infestans and Plasmopara viticola, that bring destructive damage in agricultural production. As part of the study, we established an improved Agrobacterium-mediated transformation (AMT) method by prokaryotic expression in Agrobacterium tumefaciens of AtVIP1 (VirE2-interacting protein 1), an Arabidopsis bZIP gene required for AMT but absent in oomycetes genomes. Using the new method, we achieved an increment in transformation efficiency in two P. infestans strains. We further obtained a positive GFP transformant of P. viticola using the modified AMT method. By combining this method with the CRISPR/Cas12a genome editing system, we successfully performed targeted mutagenesis and generated loss-of-function mutations in two P. infestans genes. We edited a MADS-box transcription factor-encoding gene and found that a homozygous mutation in MADS-box results in poor sporulation and significantly reduced virulence. Meanwhile, a single-copy avirulence effector-encoding gene Avr8 in P. infestans was targeted and the edited transformants were virulent on potato carrying the cognate resistance gene R8, suggesting that loss of Avr8 led to successful evasion of the host immune response by the pathogen. In summary, this study reports on a modified genetic transformation and genome editing system, providing a potential tool for accelerating molecular genetic studies not only in oomycetes, but also other microorganisms. Author summary: Oomycetes are a unique group of animal and plant pathogens that include some of the biggest threats to food security and natural ecosystems. However, much of the pathogenesis and development in these organisms remains to be learned, largely due to shortage of efficient genetic manipulation methods for a long time. In this manuscript, we developed modified Agrobacterium-mediated genetic transformation strategies for Phytophthora infestans, a notorious oomycete species that caused Irish Famine in the 19th century, and Plasmopara viticola, the causal agent of grapevine downy mildew that is known as a highly destructive disease of grapevines in all grape-growing areas of the world. Using prokaryotic expression of a plant protein in A. tumefaciens, we achieved considerable increase in transformation rate in different P. infestans strains, and also acquired one positive transformant of P. viticola, a oomycete species that is extremely hard-to-transform and cannot be grown as an axenic culture. Using our improved transformation protocol, combined with the CRISPR/Cas12a system, we performed genome editing and created loss-of-function alleles in P. infestans. In summary, our study reports on modified genetic transformation methods, for two important oomycete species, that have the potential to accelerate the molecular genetic study of many other microorganisms. [ABSTRACT FROM AUTHOR]

Plant pathogens rely on effector proteins to suppress host innate immune responses and facilitate colonization. Although the Phytophthora sojae RxLR effector Avh241 promotes Phytophthora infection, the molecular basis of Avh241 virulence remains poorly understood. Here we identified non‐race specific disease resistance 1 (NDR1)‐like proteins, the critical components in plant effector‐triggered immunity (ETI) responses, as host targets of Avh241. Avh241 interacts with NDR1 in the plasma membrane and suppresses NDR1‐participated ETI responses. Silencing of GmNDR1s increases the susceptibility of soybean to P. sojae infection, and overexpression of GmNDR1s reduces infection, which supports its positive role in plant immunity against P. sojae. Furthermore, we demonstrate that GmNDR1 interacts with itself, and Avh241 probably disrupts the self‐association of GmNDR1. These data highlight an effective counter‐defense mechanism by which a Phytophthora effector suppresses plant immune responses, likely by disturbing the function of NDR1 during infection. [ABSTRACT FROM AUTHOR]

The article presents questions and answers related to plant pathogens including what are proteins and effectors of nudix, what are the role of nudix effector during host-pathogen interaction, and do host factor has been required in nudix effector to function.

The 'zigzag' model formulates some of the fundamental principles underpinning the dynamic interactions between pathogen effectors and plant immunity. As key virulence factors, effectors often exhibit a pattern of rapid evolution, presumably as a result of the host-pathogen arms race. Here, we summarize the current knowledge of mechanisms that may accelerate effector evolution in the highly successful Phytophthora pathogens. Recent findings on epigenetic regulation of effector genes that allows evasion of host recognition and maintenance of cost/benefit balance, and a conserved structural unit in effector proteins that may promote the evolution of virulence activities are highlighted. [ABSTRACT FROM AUTHOR]

Background: Effective disease management depends on timely and accurate diagnosis to guide control measures. The capacity to distinguish between individuals in a pathogen population with specific properties such as fungicide resistance, toxin production and virulence profiles is often essential to inform disease management approaches. The genomics revolution has led to technologies that can rapidly produce high-resolution genotypic information to define individual variants of a pathogen species. However, their application to complex fungal pathogens has remained limited due to the frequent inability to culture these pathogens in the absence of their host and their large genome sizes. Results: Here, we describe the development of Mobile And Real-time PLant disEase (MARPLE) diagnostics, a portable, genomics-based, point-of-care approach specifically tailored to identify individual strains of complex fungal plant pathogens. We used targeted sequencing to overcome limitations associated with the size of fungal genomes and their often obligately biotrophic nature. Focusing on the wheat yellow rust pathogen, Puccinia striiformis f.sp. tritici (Pst), we demonstrate that our approach can be used to rapidly define individual strains, assign strains to distinct genetic lineages that have been shown to correlate tightly with their virulence profiles and monitor genes of importance. Conclusions: MARPLE diagnostics enables rapid identification of individual pathogen strains and has the potential to monitor those with specific properties such as fungicide resistance directly from field-collected infected plant tissue in situ. Generating results within 48 h of field sampling, this new strategy has far-reaching implications for tracking plant health threats. [ABSTRACT FROM AUTHOR]

A correction to the article "Nudix Effectors: A Common Weapon in the Arsenal of Plant Pathogens" that was published in the previous issue is presented.

Abstract: Oomycete plant pathogens translocate hundreds of RXLR effector proteins into host cells to establish an infection; however, the mechanism by which the effector manipulates host defence and promotes pathogenicity remains largely unknown. Here, we generated two independent transgenic Arabidopsis lines of Avh331, an RXLR effector of Phytophthora sojae, and showed that Avh331 suppresses the Arabidopsis mitogen-activated protein kinase (MAPK)-based plant defence activated by the Phytophthora elicitor to promote colonisation of the Phytophthora pathogen. Furthermore, Avh331 suppressed transcriptional activation of resistance marker genes downstream of the MAPK signalling pathway. Similar to the phenotype in Arabidopsis, Avh331 suppressed the MAPK signalling pathway to inhibit the basal defence induced by Phytophthora elicitor INF1 or tobacco MAPK proteins in Nicotiana benthamiana. Taken together, these results indicate that the RXLR effector Avh331 promoted the colonisation of plant pathogens by manipulating the MAPK signalling pathway in plant cells. [Copyright &y& Elsevier]