Effector-triggered immunity (ETI) is an active immune response triggered by interactions between host resistance proteins and their cognate effectors. Although ETI is often associated with the hypersensitive response (HR), various R genes mediate an HR-independent process known as extreme resistance (ER). In the soybean-Soybean mosaic virus (SMV) pathosystem, the strain-specific CI protein of SMV functions as an effector of Rsv3-mediated ER. In this study, we used the soybean (Rsv3)-SMV (CI) pathosystem to gain insight into the molecular signaling pathway involved in ER. We used genome-wide transcriptome analysis to identify a subset of the type 2C protein phophatase (PP2C) genes that are specifically up-regulated in Rsv3-mediated ER. Gain-of-function analysis of the most significantly expressed soybean PP2C gene, GmPP2C3a, showed that ABA-induced GmPP2C3a functions as a key regulator of Rsv3-mediated ER. Our results further suggest that the primary mechanism of ER against viruses is the inhibition of viral cell-to-cell movement by callose deposition in an ABA signaling-dependent manner.
There is a close relationship between CMBs and LV hypertrophy in hypertensive patients with stroke. Thus, CMBs should be understood as one type of cerebral target organ damage by chronic hypertension.
bThe accumulation of viral RNA depends on many host cellular factors. The hexagonal peroxisome (Hex1) protein is a fungal protein that is highly expressed when the DK21 strain of Fusarium graminearum virus 1 (FgV1) infects its host, and Hex1 affects the accumulation of FgV1 RNA. The Hex1 protein is the major constituent of the Woronin body (WB), which is a peroxisome-derived electron-dense core organelle that seals the septal pore in response to hyphal wounding. To clarify the role of Hex1 and the WB in the relationship between FgV1 and Fusarium graminearum, we generated targeted gene deletion and overexpression mutants. Although neither HEX1 gene deletion nor overexpression substantially affected vegetative growth, both changes reduced the production of asexual spores and reduced virulence on wheat spikelets in the absence of FgV1 infection. However, the vegetative growth of deletion and overexpression mutants was increased and decreased, respectively, upon FgV1 infection compared to that of an FgV1-infected wild-type isolate. Viral RNA accumulation was significantly decreased in deletion mutants but was significantly increased in overexpression mutants compared to the viral RNA accumulation in the virus-infected wild-type control. Overall, these data indicate that the HEX1 gene plays a direct role in the asexual reproduction and virulence of F. graminearum and facilitates viral RNA accumulation in the FgV1-infected host fungus.T he interactions between viral elements and host factors are important for maintaining the infection cycles of RNA viruses in host cells. Viruses utilize numerous host factors that play essential roles in virus infection. Therefore, understanding the role(s) of host factors can provide insight into the molecular mechanism(s) of host and virus interactions. Relative to host factors affecting RNA viruses of animals and plants, host factors affecting fungal viruses (mycoviruses) are poorly understood.Several host and viral components required for virus life in cells have been identified and characterized in the model organism Saccharomyces cerevisiae. The knowledge obtained by studying S. cerevisiae as a host for several double-stranded RNA (dsRNA) and single-stranded RNA (ssRNA) viruses has greatly extended our understanding of mycovirus-host interaction (1). With respect to filamentous fungi, the host factors required for mycovirus replication and symptom induction have been well described for the interaction between the prototypic hypovirus Cryphonectria hypovirus 1 strain EP713 (CHV1) and its host, the chestnut blight fungus (Cryphonectria parasitica). One of these host factors, NAM-1, modulates symptom induction in the fungus in response to CHV1 infection (2). The hypovirus-responsive host transcription factor gene pro1 is required for female fertility of C. parasitica, development of its asexual spores, and the maintenance of CHV1 infection (3). The host gene Cpbir1 (bir1 of C. parasitica), which encodes the IAP (inhibitor of apoptosis protein) CpBir1 and which is required for fungal...
The complete genomes two different dsRNA mycoviruses, Fusarium graminearum virus 3 (FgV3) and Fusarium graminearum virus 4 (FgV4), was sequenced and analyzed. The viral genome of FgV3 is 9,098 base pairs (bp) long and contains two open reading frames (ORF) encoding a putative RNA-dependent RNA polymerase (RdRp) and a protein of unknown function. The FgV4 genome is composed of two dsRNA genome segments of 2,383 bp and 1,739 bp. FgV4 dsRNA-1 contains a single ORF, which has a conserved RdRp motif, while FgV4 dsRNA-2 contains two putative ORFs coding for products of unknown function. Both the genome organization and phylogenetic analysis indicated that FgV3 was closely related to members of the families Totiviriridae and Chrysoviridae, but it was placed outside of their main clusters, whereas FgV4 formed a distinct clade with the family Partitiviridae. This is the first report of the full-length nucleotide sequences of FgV3 and FgV4 infecting Fusarium graminearum.
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