Identification of miRNAs involved in fruit ripening in Cavendish bananas by deep sequencing

The most enriched pathways that were identified for the target genes. A total of 53 most enriched pathways of target gene annotated in this study. (XLS 41 kb

RI/MOM and RI/SMOM renormalization of quark bilinear operators using the overlap fermion

We present the vector, scalar and tensor renormalization constants (RCs) using the overlap fermion on dynamical fermion gauge configurations with either the Domain wall fermion action or HISQ actions, using RI/MOM and RI/SMOM as the intermediate scheme at the lattice spacing $a$ from 0.04 fm to 0.12 fm. The results show that RI/MOM and RI/SMOM can provide consistent renormalization constants under the $\bar{\textrm{MS}}$ scheme, after proper $a^2p^2$ extrapolations. But at $p\sim 2$ GeV, both the RI/MOM and RI/SMOM suffer from nonperturbative effects which cannot be removed by the perturbative matching. The comparison between the results with different sea actions also suggests that the renormalization constant is discernibly sensitive to the lattice spacing but not to the bare gauge coupling in the gauge action.Comment: 21 pages, 15 figure

Carbon regulation of environmental pH by secreted small molecules that modulate pathogenicity in phytopathogenic fungi

[EN]Fruit pathogens can contribute to the acidification or alkalinization of the host environment. This capability has been used to divide fungal pathogens into acidifying and/or alkalinizing classes. Here, we show that diverse classes of fungal pathogens—Colletotrichum gloeosporioides, Penicillium expansum, Aspergillus nidulans and Fusarium oxysporum—secrete small pH-affecting molecules. These molecules modify the environmental pH, which dictates acidic or alkaline colonizing strategies, and induce the expression of PACC-dependent genes. We show that, in many organisms, acidification is induced under carbon excess, i.e. 175 mm sucrose (the most abundant sugar in fruits). In contrast, alkalinization occurs under conditions of carbon deprivation, i.e. less than 15 mm sucrose. The carbon source is metabolized by glucose oxidase (gox2) to gluconic acid, contributing to medium acidification, whereas catalysed deamination of non-preferred carbon sources, such as the amino acid glutamate, by glutamate dehydrogenase 2 (gdh2), results in the secretion of ammonia

CgGCS, Encoding a Glucosylceramide Synthase, Is Required for Growth, Conidiation and Pathogenicity in Colletotrichum gloeosporioides

Fungal glucosylceramide plays important role in cell division, hyphal formation and growth, spore germination and the modulation of virulence and has recently been considered as target for small molecule inhibitors. In this study, we characterized CgGCS, a protein encoding a glucosylceramide synthase (GCS) in Colletotrichum gloeosporioides. Disruption of CgGCS resulted in a severe reduction of mycelial growth and defects in conidiogenesis. Sphingolipid profile analysis revealed large decreases in glucosylceramide production in the mutant strains. Pathogenicity assays indicated that the ability of the ΔCgGCS mutants to invade both tomato and mango hosts was almost lost. In addition, the expression levels of many genes, especially those related to metabolism, were shown to be affected by the mutation of CgGCS via transcriptome analysis. Overall, our results demonstrate that C. gloeosporioides glucosylceramide is an important regulatory factor in fungal growth, conidiation, and pathogenesis in hosts

Fusaric acid instigates the invasion of banana by Fusarium oxysporum f. sp. cubense TR4

CITATION: Liu, S. et al. 2020. Fusaric acid instigates the invasion of banana by Fusarium oxysporum f. sp. cubense TR4. New Phytologist, 225:913–929, doi:10.1111/nph.16193.The original publication is available at https://nph.onlinelibrary.wiley.comFusaric acid (FSA) is a phytotoxin produced by several Fusarium species and has been associated with plant disease development, although its role is still not well understood. Mutation of key genes in the FSA biosynthetic gene (FUB) cluster in Fusarium oxysporum f. sp. cubense tropical race 4 (Foc TR4) reduced the FSA production, and resulted in decreased disease symptoms and reduced fungal biomass in the host banana plants. When pretreated with FSA, both banana leaves and pseudostems exhibited increased sensitivity to Foc TR4 invasion. Banana embryogenic cell suspensions (ECSs) treated with FSA exhibited a lower rate of O2 uptake, loss of mitochondrial membrane potential, increased reactive oxygen species (ROS) accumulation, and greater nuclear condensation and cell death. Consistently, transcriptomic analysis of FSA-treated ECSs showed that FSA may induce plant cell death through regulating the expression of genes involved in mitochondrial functions. The results herein demonstrated that the FSA from Foc TR4 functions as a positive virulence factor and acts at the early stage of the disease development before the appearance of the fungal hyphae in the infected tissues.https://nph.onlinelibrary.wiley.com/doi/full/10.1111/nph.16193Publisher's versio

How Does Host Carbon Concentration Modulate the Lifestyle of Postharvest Pathogens during Colonization?

Postharvest pathogens can penetrate fruit by breaching the cuticle or directly through wounds, remain quiescent and they show disease symptoms only long after infection. During ripening and senescence, the fruit undergo physiological processes accompanied by a decline in antifungal compounds, which allows the pathogen to activate a mechanism of secretion of small effector molecules that modulate host environmental pH. This results in the transcript activation of fungal genes under their optimal pH conditions, enabling the fungus to use a specific group of pathogenicity factors at each particular pH. New research suggests that carbon availability in the environment of the activating pathogen is a key factor triggering the production and secretion of small pH-modulating molecules: ammonia and organic acid. Ammonia is secreted under limited carbon and gluconic acid under excess carbon. This mini review describes our most recent knowledge on the mechanism of activation of the biosynthesis and secretion of fungal molecules that modulate the host pH, and their contribution to the transition from quiescence to necrotrophic lifestyle by the postharvest pathogens

The pH modulation by fungal secreted molecules: a mechanism affecting pathogenicity by postharvest pathogens

A postharvest pathogen can start its attack process as soon as spores land on wounded tissue; other pathogens breach the unripe fruit cuticle, remain quiescent for months until the fruit ripens, and then cause major losses. Postharvest fungal pathogens initiate their development by secreting organic acids or ammonia, which acidify or alkalinize the ambient host environment, respectively. These fungal secreted molecules (SM) modulate the host environment and regulate an arsenal of enzymes in order to increase fungal pathogenicity under any specific conditions. Furthermore, accumulation of these SMs (organic acids and ammonia) is multifunctional and, together with their effect on the ambient pH, they activate virulence factors to further enhance their necrotrophic attack. Interestingly, similar arsenals of genes were detected in species with differing acidifying and alkalizing modes of attack. Recently, the mechanism of switching the acidification and alkalization processes was found to be regulated by the carbon levels present in the host. Based on this regulation process, it will be possible to foresee the fungal activation of acid- and/or alkaline-expressed genes and their contribution to pathogenicity.</jats:p

Combined Application of Malic Acid and Lycopene Maintains Content of Phenols, Antioxidant Activity, and Membrane Integrity to Delay the Pericarp Browning of Litchi Fruit During Storage

Litchi fruit contains abundant polyphenols and is susceptible to browning after harvest. Herein the combined treatments of malic acid (MA) and lycopene (LYC) to delay the development of browning in litchi fruit stored at room temperature (25°C) and low temperature (4°C) was investigated. The results showed that the pericarp browning could be alleviated, and the increase of malondialdehyde (MDA) content and relative leakage rate was retarded by the combined MA and LYC during storage. As compared to control, the content of pericarp anthocyanins, flavonoids, and the total phenols maintained higher levels; and the decrease of antioxidant activity of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity and reducing power were slowed down in treated fruit. The enzyme activity of polyphenol oxidase (PPO) and peroxidase (POD) related to oxidation of polyphenols were depressed by the combined treatments. Furthermore, correlation analysis revealed that the content of phenols in the pericarp negatively affected the changes in the browning index, and was positively related to the DPPH radical scavenging capacity. Taken together, the combined treatments of MA and LYC exhibited potential effects in delaying the pericarp browning of litchi fruit by maintaining the content of polyphenols, antioxidant activity, and membrane integrity.</jats:p

Changes of Morphology, Chemical Compositions, and the Biosynthesis Regulations of Cuticle in Response to Chilling Injury of Banana Fruit During Storage

The plant cuticle covers almost all the outermost surface of aerial plant organs, which play a primary function in limiting water loss and responding to the environmental interactions. Banana fruit is susceptible to thermal changes with chilling injury below 13°C and green ripening over 25°C. Herein, the changes of surface morphology, chemical compositions of cuticle, and the relative expression of cuticle biosynthesis genes in banana fruit under low-temperature storage were investigated. Banana fruit exhibited chilling injury rapidly with browned peel appearance stored at 4°C for 6 days. The surface altered apparently from the clear plateau with micro-crystals to smooth appearance. As compared to normal ones, the overall coverage of the main cuticle pattern of waxes and cutin monomers increased about 22% and 35%, respectively, in browned banana stored under low temperature at 6 days. Fatty acids (C16–C18) and ω-OH, mid-chain-epoxy fatty acids (C18) dominated cutin monomers. The monomers of fatty acids, the low abundant ω, mid-chain-diOH fatty acids, and 2-hydroxy fatty acids increased remarkably under low temperature. The cuticular waxes were dominated by fatty acids (&amp;gt; C19), n-alkanes, and triterpenoids; and the fatty acids and aldehydes were shifted to increase accompanied by the chilling injury. Furthermore, RNA-seq highlighted 111 cuticle-related genes involved in fatty acid elongation, biosynthesis of very-long-chain (VLC) aliphatics, triterpenoids, and cutin monomers, and lipid-transfer proteins were significantly differentially regulated by low temperature in banana. Results obtained indicate that the cuticle covering on the fruit surface was also involved to respond to the chilling injury of banana fruit after harvest. These findings provide useful insights to link the cuticle on the basis of morphology, chemical composition changes, and their biosynthesis regulations in response to the thermal stress of fruit during storage.</jats:p