ANGUSTIFOLIA negatively regulates resistance to Sclerotinia sclerotiorum via modulation of PTI and JA signalling pathways in Arabidopsis thaliana.

Sclerotinia sclerotiorum is a devastating pathogen that infects a broad range of host plants. The mechanism underlying plant defence against fungal invasion is still not well characterized. Here, we report that ANGUSTIFOLIA (AN), a CtBP family member, plays a role in the defence against S. sclerotiorum attack. Arabidopsis an mutants exhibited stronger resistance to S. sclerotiorum at the early stage of infection than wild-type plants. Accordingly, an mutants exhibited stronger activation of pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) responses, including mitogen-activated protein kinase activation, reactive oxygen species accumulation, callose deposition, and the expression of PTI-responsive genes, upon treatment with PAMPs/microbe-associated molecular patterns. Moreover, Arabidopsis lines overexpressing AN were more susceptible to S. sclerotiorum and showed defective PTI responses. Our luminometry, bimolecular fluorescence complementation, coimmunoprecipitation, and in vitro pull-down assays indicate that AN interacts with allene oxide cyclases (AOC), essential enzymes involved in jasmonic acid (JA) biosynthesis, negatively regulating JA biosynthesis in response to S. sclerotiorum infection. This work reveals AN is a negative regulator of the AOC-mediated JA signalling pathway and PTI activation.

Arabidopsis pavement cell morphogenesis requires FERONIA binding to pectin for activation of ROP GTPase signaling.

Sensing and signaling of cell wall status and dynamics regulate many processes in plants, such as cell growth and morphogenesis, but the underpinning mechanisms remain largely unknown. Here, we demonstrate that the CrRLK1L receptor kinase FERONIA (FER) binds the cell wall pectin, directly leading to the activation of the ROP6 guanosine triphosphatase (GTPase) signaling pathway that regulates the formation of the puzzle piece shape of pavement cells in Arabidopsis. The extracellular malectin domain of FER binds demethylesterified pectin in vivo and in vitro. Both loss-of-FER mutations and defects in pectin demethylesterification caused similar changes in pavement cell shape and ROP6 GTPase signaling. FER is required for the activation of ROP6 by demethylesterified pectin and physically and genetically interacts with the ROP6 activator, RopGEF14. Thus, our findings elucidate a signaling pathway that directly connects the cell wall pectin to cellular morphogenesis via the cell surface receptor FER.

Genome Sequence of Venturia oleaginea, the Causal Agent of Olive Leaf Scab.

Olive leaf scab, also known as peacock spot disease, caused by Venturia oleaginea (syn. Spilocaea oleaginea and Fusicladium oleagineum) is the most widespread and economically important fungal disease attacking olive in production countries. Here, we report the first highly contiguous whole-genome sequence (46.08 Mb) of one isolate, YUN35, of V. oleaginea. The described genome sequence and annotation resource will be useful to study the fungal biology, pathogen-host interaction, characterization of genes of interest, and population genetic diversity.

Endoplasmic reticulum-associated degradation mediated by MoHrd1 and MoDer1 is pivotal for appressorium development and pathogenicity of Magnaporthe oryzae.

Most secretory proteins are folded and modified in the endoplasmic reticulum (ER); however, protein folding is error-prone, resulting in toxic protein aggregation and cause ER stress. Irreversibly misfolded proteins are subjected to ER-associated degradation (ERAD), modified by ubiquitination, and degraded by the 26S proteasome. The yeast ERAD ubiquitin ligase Hrd1p and multispanning membrane protein Der1p are involved in ubiquitination and transportation of the folding-defective proteins. Here, we performed functional characterization of MoHrd1 and MoDer1 and revealed that both of them are localized to the ER and are pivotal for ERAD substrate degradation and the ER stress response. MoHrd1 and MoDer1 are involved in hyphal growth, asexual reproduction, infection-related morphogenesis, protein secretion and pathogenicity of M. oryzae. Importantly, MoHrd1 and MoDer1 mediated conidial autophagic cell death and subsequent septin ring assembly at the appressorium pore, leading to abnormal appressorium development and loss of pathogenicity. In addition, deletion of MoHrd1 and MoDer1 activated the basal unfolded protein response (UPR) and autophagy, suggesting that crosstalk between ERAD and two other closely related mechanisms in ER quality control system (UPR and autophagy) governs the ER stress response. Our study indicates the importance of ERAD function in fungal development and pathogenesis of M. oryzae.

The deubiquitinating enzyme MoUbp8 is required for infection-related development, pathogenicity, and carbon catabolite repression in Magnaporthe oryzae.

Deubiquitination is an essential regulatory step in the Ub-dependent pathway. Deubiquitinating enzymes (DUBs) mediate the removal of ubiquitin moieties from substrate proteins, which are involved in many regulatory mechanisms. As a component of the DUB module (Ubp8/Sgf11/Sus1/Sgf73) in the SAGA (Spt-Ada-Gcn5-acetyltransferase) complex, Ubp8 plays a crucial role in both Saccharomyces cerevisiae and humans. In S. cerevisiae, Ubp8-mediated deubiquitination regulates transcriptional activation processes. To investigate the contributions of Ubp8 to physiological and pathological development of filamentous fungi, we generated the deletion mutant of ortholog MoUBP8 (MGG-03527) in Magnaporthe oryzae (syn. Pyricularia oryzae). The ΔMoubp8 strain showed reduced sporulation, pathogenicity, and resistance to distinct stresses. Even though the conidia of the ΔMoubp8 mutant were delayed in appressorium formation, the normal and abnormal (none-septum or one-septum) conidia could finally form appressoria. Reduced melanin in the ΔMoubp8 mutant is highly responsible for the attenuated pathogenicity since the appressoria of the ΔMoubp8 mutant was much more fragile than those of the wild type, due to the defective turgidity. The weakened ability to detoxify or scavenge host-derived reactive oxygen species (ROS) further restricted the invasion of the pathogen. We also showed that carbon derepression, on the one hand, rendered the ΔMoubp8 strain highly sensitive to allyl alcohol, on the other hand, it enhances the resistance of the MoUBP8 defective strain to deoxyglucose. Overall, we suggest that MoUbp8 is not only required for sporulation, melanin formation, appressoria development, and pathogenicity but also involved in carbon catabolite repression of M. oryzae.