Ageing results from complex genetically and epigenetically programmed processes that are elicited in part by noxious or stressful events that cause programmed cell death Here, we report that administration of spermidine, a natural polyamine whose intracellular concentration declines during human ageing, markedly extended the lifespan of yeast, flies and worms, and human immune cells In addition, spermidine administration potently inhibited oxidative stress in ageing mice In ageing yeast, spermidine treatment triggered epigenetic deacetylation of histone H3 through inhibition of histone acetyltransferases (HAT), suppressing oxidative stress and necrosis Conversely, depletion of endogenous polyamines led to hyperacetylation, generation of reactive oxygen species, early necrotic death and decreased lifespan The altered acetylation status of the chromatin led to significant upregulation of various autophagy-related transcripts, triggering autophagy in yeast, flies, worms and human cells Finally, we found that enhanced autophagy is crucial for polyamine-induced suppression of necrosis and enhanced longevity

Induction of autophagy by spermidine promotes longevity

Fibrosis is the major pathological feature of diabetic kidney disease (DKD). Autophagy, a process to maintain metabolic homeostasis, is obviously inhibited in DKD. Triptolide (TP) is a traditional Chinese medicine extract known for immune suppression and anti-inflammatory and anti-cancer activities. In this study, we investigated the effects of TP on autophagy and fibrosis in DKD. TP restored autophagy and alleviated fibrosis in DKD rats and high-glucose-incubated human mesangial cells. After we applied 3-methyladenine (an autophagy inhibitor) and autophagy-related gene 5-small interfering RNA (siRNA), we found that the improvement of fibrosis on TP was related to the restoration of autophagy. In addition, miR-141-3p levels were increased under high glucose but reduced after TP treatment. miR-141-3p overexpression aggravated the fibrosis and restrained the autophagy further, while miR-141-3p inhibition imitated the effects of TP. As an action target, phosphatase and tensin homolog (PTEN) showed corresponding opposite changes. After PTEN-siRNA transfection, the effects of TP on autophagy and fibrosis were inhibited. PTEN levels were downregulated, with downstream phosphorylated protein kinase B (Akt) and the mammalian target of rapamycin (mTOR) upregulated in high glucose, which were reversed by TP treatment. These findings indicate that TP alleviates fibrosis by restoring autophagy through the miR-141-3p/PTEN/Akt/mTOR pathway and is a novel therapeutic option for DKD.

Triptolide Restores Autophagy to Alleviate Diabetic Renal Fibrosis through the miR-141-3p/PTEN/Akt/mTOR Pathway

The interaction between pathogens and their host plants is a ubiquitous process. Some plant fungal pathogens can form a specific infection structure, such as an appressorium, which is formed by the accumulation of a large amount of glycerin and thereby the creation of an extremely high intracellular turgor pressure, which allows the penetration peg of the appressorium to puncture the leaf cuticle of the host. Previous studies have shown that autophagy energizes the accumulation of pressure by appressoria, which induces its pathogenesis. Similar to other eukaryotic organisms, autophagy processes are highly conserved pathways that play important roles in filamentous fungal pathogenicity. This review aims to demonstrate how the autophagy process affects the pathogenicity of plant pathogens.

https://www.tandfonline.com/doi/pdf/10.1080/21505594.2018.1551011

Current opinions on autophagy in pathogenicity of fungi.

The plant secretome is usually considered in the frame of proteomics, aiming at characterizing extracellular proteins, their biological roles and the mechanisms accounting for their secretion in the extracellular space. In this review, we aim to highlight recent results pertaining to secretion through the conventional and unconventional protein secretion pathways notably those involving plant exosomes or extracellular vesicles. Furthermore, plants are well known to actively secrete a large array of different molecules from polymers (e.g. extracellular RNA and DNA) to small compounds (e.g. ATP, phytochemicals, secondary metabolites, phytohormones). All of these play pivotal roles in plant-fungi (or oomycetes) interactions, both for beneficial (mycorrhizal fungi) and deleterious outcomes (pathogens) for the plant. For instance, recent work reveals that such secretion of small molecules by roots is of paramount importance to sculpt the rhizospheric microbiota. Our aim in this review is to extend the definition of the plant and fungal secretomes to a broader sense to better understand the functioning of the plant/microorganisms holobiont. Fundamental perspectives will be brought to light along with the novel tools that should support establishing an environment-friendly and sustainable agriculture.

/pdf/the-multiple-facets-of-plant-fungal-interactions-revealed-47uniwljq3.pdf

The Multiple Facets of Plant-Fungal Interactions Revealed Through Plant and Fungal Secretomics.

Macroautophagy/autophagy is critical for normal appressorium formation and pathogenicity of the rice blast fungus Magnaporthe oryzae, but the molecular base of autophagy linked to pathogenicity remains elusive in this or other pathogenic fungi. We found that MoHat1, a histone acetyltransferase (HAT) homolog, had a role in the regulation of autophagy through the acetylation of autophagy related proteins MoAtg3 and MoAtg9. We also found that MoHat1 was subject to regulation by the protein kinase MoGsk1 that modulated the translocation of MoHat1 from the nucleus to the cytoplasm with the assistance of MoSsb1, a protein chaperone. The alternation of intracellular location affected MoHat1 in the modification of cytosolic autophagy proteins that maintained normal autophagy. Furthermore, we provided evidence linking acetylation of MoAtg3 and MoAtg9 by MoHat1 to functional appressorium development and pathogenicity. Together with the first report of MoAtg9 being subject to acetylation regulation by MoHat1, our studies depicted how MoHat1 regulated autophagy in conjunction with MoGsk1 and how normal autophagy was linked to appressorium formation and function and pathogenicity of M. oryzae. Abbreviations: A/Ala: alanine; AP: autophagosome; Atg genes/proteins: autophagy-related genes/proteins; BiFC: bimolecular fluorescence complementation; co-IP: co-immunoprecipitation; DAPI: 4', 6-diamidino-2-phenylindole; D/Asp: aspartic acid; GFP: green fluorescent protein; GSK3: glycogen synthase kinase 3; HAT: histone acetyltransferase; Hsp70: heat-shock protein 70; IH: invasive hyphae; K/Lys: lysine; MMS: methyl methanesulfonate; Mo: Magnaporthe oryzae; PAS: phagophore assembly site; PE: phosphatidylethanolamine; PtdIns3K: phosphatidylinositol 3-kinase; R/Arg: arginine; S/Ser: serine; T/Thr: threonine; TOR: target of rapamycin; WT: wild type; YFP: yellow fluorescent protein.

Histone acetyltransferase MoHat1 acetylates autophagy-related proteins MoAtg3 and MoAtg9 to orchestrate functional appressorium formation and pathogenicity in Magnaporthe oryzae

Magnaporthe oryzae, the ascomycete fungus that causes rice blast disease, initiates conidiation in response to light when grown on Prune-Agar medium containing both carbon and nitrogen sources. Macroautophagy/autophagy was shown to be essential for M. oryzae conidiation and induced specifically upon exposure to light but is undetectable in the dark. Therefore, it is inferred that autophagy is naturally induced by light, rather than by starvation during M. oryzae conidiation. However, the signaling pathway(s) involved in such phototropic induction of autophagy remains unknown. We identified an M. oryzae ortholog of GCN5 (MGG_03677), encoding a histone acetyltransferase (HAT) that negatively regulates light- and nitrogen-starvation-induced autophagy, by acetylating the autophagy protein Atg7. Furthermore, we unveiled novel regulatory mechanisms on Gcn5 at both transcriptional and post-translational levels, governing its function associated with the unique phototropic response of autophagy in this pathogenic fungus. Thus, our study depicts a signaling network and regulatory mechanism underlying the autophagy induction by important environmental clues such as light and nutrients.

https://www.tandfonline.com/doi/pdf/10.1080/15548627.2017.1327103

Phototrophy and starvation-based induction of autophagy upon removal of Gcn5-catalyzed acetylation of Atg7 in Magnaporthe oryzae.

The rice blast fungus Magnaporthe oryzae poses a great threat to global food security. During its conidiation (asexual spore formation) and appressorium (infecting structure) formation, autophagy is induced, serving glycogen breakdown or programmed cell death function, both essential for M. oryzae pathogenicity. Recently, we identified an M. oryzae histone acetyltransferase (HAT) Gcn5 as a key regulator in phototropic induction of autophagy and asexual spore formation while serving a cellular function other than autophagy induction during M. oryzae infection. To further understand the regulatory mechanism of Gcn5 on M. oryzae pathogenicity, we set out to identify more Gcn5 substrates by comparative acetylome between the wild-type (WT) and GCN5 overexpression (OX) mutant and between OX mutant and GCN5 deletion (knockout [KO]) mutant. Our results showed that Gcn5 regulates autophagy induction and other important aspects of fungal pathogenicity, including energy metabolism, stress response, cell toxicity and death, likely via both epigenetic regulation (histone acetylation) and posttranslational modification (nonhistone protein acetylation). IMPORTANCE Gcn5 is a histone acetyltransferase that was previously shown to regulate phototropic and starvation-induced autophagy in the rice blast fungus Magnaporthe oryzae, likely via modification on autophagy protein Atg7. In this study, we identified more potential substrates of Gcn5-mediated acetylation by quantitative and comparative acetylome analyses. By epifluorescence microscopy and biochemistry experiments, we verified that Gcn5 may regulate autophagy induction at both the epigenetic and posttranslational levels and regulate autophagic degradation of a critical metabolic enzyme pyruvate kinase (Pk) likely via acetylation. Overall, our findings reveal comprehensive posttranslational modification executed by Gcn5, in response to various external stimuli, to synergistically promote cellular differentiation in a fungal pathogen.

Label-Free Quantitative Proteomics of Lysine Acetylome Identifies Substrates of Gcn5 in Magnaporthe oryzae Autophagy and Epigenetic Regulation.

Phytohormones (also named as plant hormones) are chemicals produced by plants in order to modulate various aspects of plant development, stress responses and defence. Recent studies revealed that fungi can also produce phytohormones or phytohormone-mimiking molecules, while it remains poorly understood about the details in the role and regulatory mechanism of such fungal produced phytohormonal molecules in plant-fungus interactions. The rice-blast fungus Magnaporthe oryzae imposes a great threat to global food security. Intensive investigation has been conducted to elucidate M. oryzae pathogenicity and rice (Oryza sativa L.) defense mechanism against blast disease, in order to provide theoretical basis and/or identify potential target(s) for developing novel disease control strategies, as well as for breeding of resistance varieties. Phytohormones have been demonstrated to play conserved and divergent roles in fine-tuning the balance of rice growth and immunity towards M. oryzae. Meanwhile, M. oryzae evolved elaborate strategy to manipulate the rice phytohormones metabolism, or even directly produce and secrete phytohormones, during their invasion process. In this review, we discuss the chemical communication in term of phytohormones in M. oryzae-rice pathosystem.

https://www.tandfonline.com/doi/pdf/10.1080/21501203.2018.1483441

Phytohormones: the chemical language in Magnaporthe oryzae-rice pathosystem.

Nuclear import of proteins relies on nuclear import receptors called importins/karyopherins (Kaps), whose functions were reported in yeasts, fungi, plants, and animal cells, including cell cycle control, morphogenesis, stress sensing/response, and also fungal pathogenecity. However, limited is known about the physiological function and regulatory mechanism of protein import in the rice-blast fungus Magnaporthe oryzae. Here, we identified an ortholog of β-importin in M. oryzae encoded by an ortholog of KAP119 gene. Functional characterisation of this gene via reverse genetics revealed that it is required for vegetative growth, conidiation, melanin pigmentation, and pathogenicity of M. oryzae. The mokap119Δ mutant was also defective in formation of appressorium-like structure from hyphal tips. By affinity assay and liquid chromatography-tandem mass spectrometry, we identified potential MoKap119-interacting proteins and further verified that MoKap119 interacts with the cyclin-dependent kinase subunit MoCks1 and mediates its nuclear import. Transcriptional profiling indicated that MoKap119 may regulate transcription of infection-related genes via MoCks1 regulation of MoSom1. Overall, our findings provide a novel insight into the regulatory mechanism of M. oryzae pathogenesis likely by MoKap119-mediated nuclear import of the cyclin-dependent kinase subunit MoCks1.

Shulin Zhang

Papers

Phototrophy and starvation-based induction of autophagy upon removal of Gcn5-catalyzed acetylation of Atg7 in Magnaporthe oryzae.

Label-Free Quantitative Proteomics of Lysine Acetylome Identifies Substrates of Gcn5 in Magnaporthe oryzae Autophagy and Epigenetic Regulation.

Phytohormones: the chemical language in Magnaporthe oryzae-rice pathosystem.

Karyopherin MoKap119-mediated nuclear import of cyclin-dependent kinase regulator MoCks1 is essential for Magnaporthe oryzae pathogenicity.