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Verticillium dahliae is a devastating pathogenic fungus that causes severe vascular wilts in more than 400 dicotyledonous plants. The conidiation of V. dahliae in plant vascular tissues is the key strategy for its adaptation to the nutrient‐poor environment and is required for its pathogenicity. However, it remains unclear about the regulatory mechanism of conidium production of V. dahliae in vascular tissues. Here, we found that VdAsp1, encoding an inositol polyphosphate kinase, is indispensable for the pathogenicity of V. dahliae. Loss of VdAsp1 function does not affect the invasion of the host, but it impairs the colonization and proliferation in vascular tissues. The ΔVdAsp1 mutant shows defective initiation of conidiophore formation and reduced expression of genes associated with the central developmental pathway. By live‐cell imaging, we observed that some of ΔVdAsp1 mutant hyphae are swollen, and microtubule arrangements at the apical region of these hyphae are disorganized. These results indicate that VdAsp1 regulates the transition from vegetative growth to asexual reproduction by modulating microtubule dynamic organization, which is essential for V. dahliae to colonize and proliferate in vascular tissues. These findings provided a potential new direction in the control of vascular wilt pathogen by targeting conidium production in vascular tissues. [ABSTRACT FROM AUTHOR]

Summary: The soil‐borne ascomycete Verticillium dahliae causes wilt disease in more than two hundred dicotyledonous plants including the economically important crop cotton, and results in a severe reduction in cotton fiber yield and quality. During infection, V. dahliae secretes numerous secondary metabolites, which act as toxic factors to promote the infection process. However, the mechanism underlying how V. dahliae secondary metabolites regulate cotton infection remains largely unexplored. In this study, we report that VdBre1, an ubiquitin ligase (E3) enzyme to modify H2B, regulates radial growth and conidia production of V. dahliae. The VdBre1 deletion strains show nonpathogenic symptoms on cotton, and microscopic inspection and penetration assay indicated that penetration ability of the ∆VdBre1 strain was dramatically reduced. RNA‐seq revealed that a total of 1643 differentially expressed genes between the ∆VdBre1 strain and the wild type strain V592, among which genes related to lipid metabolism were significantly overrepresented. Remarkably, the volume of lipid droplets in the ∆VdBre1 conidia was shown to be smaller than that of wild‐type strains. Further metabolomics analysis revealed that the pathways of lipid metabolism and secondary metabolites, such as steroid biosynthesis and metabolism of terpenoids and polyketides, have dramatically changed in the ∆VdBre1 metabolome. Taken together, these results indicate that VdBre1 plays crucial roles in cotton infection and pathogenecity, by globally regulating lipid metabolism and secondary metabolism of V. dahliae. [ABSTRACT FROM AUTHOR]

Microtubule-dependent microtubule nucleation occurs on the lateral surface of pre-existing microtubules and provides a highly efficient means of amplifying their populations and reorganizing their architectures. The γ‑tubulin ring complex serves as the template to initiate nascent microtubule polymerization. Augmin, a hetero-octameric protein complex, acts as a recruiting factor to target the γ‑tubulin ring complex to pre-existing microtubules and trigger new microtubule growth. Although microtubule-dependent microtubule nucleation has been extensively studied in both animal and plant cells, it remains unclear how the augmin complex assembles in plant cells, especially in cell-cycle-specific and cell-type-specific manners, and how its spatial structure orchestrates the nucleation geometry. In this review, we summarize the advances in knowledge of augmin-dependent microtubule nucleation and the regulation of its geometry, and highlight recent findings and emerging questions concerning the role of the augmin complex in establishing microtubule arrays and the cell-cycle-specific composition of augmin in plant cells. [ABSTRACT FROM AUTHOR]

Summary: Numerous fluorescent marker lines are currently available to visualize microtubule (MT) architecture and dynamics in living plant cells, such as markers expressing p35S::GFP‐MBD or p35S::GFP‐TUB6. However, these MT marker lines display obvious defects that affect plant growth or produce unstable fluorescent signals. Here, a series of new marker lines were developed, including the pTUB6::VisGreen‐TUB6‐expressing line in which TUB6 is under the control of its endogenous regulatory elements and eGFP is replaced with VisGreen, a brighter fluorescent protein. Moreover, two different markers were combined into one expression vector and developed two dual‐marker lines. These marker lines produce bright, stable fluorescent signals in various tissues, and greatly shorten the screening process for generating dual‐marker lines. These new marker lines provide a novel resource for MT research. We developed a series of new marker lines including dual‐marker lines for better observing spatial organization and dynamics of the microtubule in plant living cells. These marker lines produce bright, stable fluorescent signals in various tissues, and greatly shorten the screening process in generating dual‐marker lines. [ABSTRACT FROM AUTHOR]

Summary: Powdery mildew is one of the most devastating diseases of wheat. To date, few powdery mildew resistance genes have been cloned from wheat due to the size and complexity of the wheat genome. Triticum urartu is the progenitor of the A genome of wheat and is an important source for powdery mildew resistance genes. Using molecular markers designed from scaffolds of the sequenced T. urartu accession and standard map‐based cloning, a powdery mildew resistance locus was mapped to a 356‐kb region, which contains two nucleotide‐binding and leucine‐rich repeat domain (NB‐LRR) protein‐encoding genes. Virus‐induced gene silencing, single‐cell transient expression, and stable transformation assays demonstrated that one of these two genes, designated Pm60, confers resistance to powdery mildew. Overexpression of full‐length Pm60 and two allelic variants in Nicotiana benthamiana leaves induced hypersensitive cell death response, but expression of the coiled‐coil domain alone was insufficient to induce hypersensitive response. Yeast two‐hybrid, bimolecular fluorescence complementation and luciferase complementation imaging assays showed that Pm60 protein interacts with its neighboring NB‐containing protein, suggesting that they might be functionally related. The identification and cloning of this novel wheat powdery mildew resistance gene will facilitate breeding for disease resistance in wheat. [ABSTRACT FROM AUTHOR]

Summary: The vascular wilt fungus Verticillium dahliae is one of the most destructive pathogens of cotton (Gossypium hirsutum) and many other economically important dicot plants. Fungal pathogens require Myosin‐mediated actomyosin motility system for colonization of their host plants; however, the mechanisms underlying this process have not been fully characterized for V. dahliae. Here, in a knock‐out experiment, we characterized the role of VdMyo5, a member of the Myosin V family, before and during infection of cotton and Arabidopsis thaliana. The VdMyo5 deletion mutant (ΔVdmyo5) fungi showed obvious defects in the development of conidia and the polarized elongation of vegetative hyphae, but no inhibition of host root penetration. Overall, the ΔVdmyo5 fungi exhibited dramatically reduced virulence in cotton and Arabidopsis, with almost no colonization in sections of host vascular tissue. We found labelled Myosin5‐GFP to be specifically enriched at the hyphal tip, co‐localized with FM4‐64 labelled Spitzenkörper, which is the vesicle supply centre in filamentous fungi. Comparative secretome analysis revealed that proteins associated with cell wall modification and degradation of reactive oxygen species were significantly altered in mutant strains. Our results indicate that Myosin5 is required for vegetative growth and full virulence, possibly by regulating vesicle transport. The findings provide important insight into the cellular mechanisms of Verticillium pathogenesis. [ABSTRACT FROM AUTHOR]

Microtubule (MT) nucleation and organization depend on the evolutionarily conserved protein γ -tubulin, which forms a complex with GCP2-GCP6 (GCP for γ -Tubulin Complex Protein). To date, it is still unclear how GCP4-GCP6 (the non-core GCPs) may be involved in acentrosomal MT nucleation in plant cells. We found that GCP4 was associated with γ -tubulin in vivo in Arabidopsis thaliana. When GCP4 expression was repressed by an artificial microRNA, transgenic plants exhibited phenotypes of dwarfism and reduced organ size. In mitotic cells, it was observed that the γ -tubulin signal associated with the mitotic spindle, and the phragmoplast was depleted when GCP4 was downregulated. Consequently, MTs failed to converge at unified spindle poles, and the bipolar phragmoplast MT array frequently had discrete bundles with extended minus ends, resulting in failed cytokinesis as reflected by cell wall stubs in leaf epidermal cells. In addition, cortical MTs in swollen guard cells and pavement cells of the leaf epidermis became hyperparallel and bundled, which was likely caused by frequent MT nucleation with shallow angles on the wall of extant MTs. Therefore, our results support the notion that GCP4 is an indispensable component for the function of γ -tubulin in MT nucleation and organization in plant cells. [ABSTRACT FROM AUTHOR]