Blue Mold Decay Research Articles

Hannaella sinensis, a promising biocontrol agent for combating postharvest pear fruit diseases and patulin degradation

Postharvest pear fruits are susceptible to fungal decay and patulin (PAT) contamination during storage and transportation. PAT is a harmful mycotoxin contaminant of fruits and fruit products. Our team has identified a strain of Hannaella sinensis through preliminary research and validated its ability to degrade PAT in vitro. However, whether H. sinensis can effectively combat postharvest diseases of pears and control PAT within the fruit was yet unknown. Therefore, our current work aimed to determine the ability of H. sinensis to control blue mold decay and PAT contamination in postharvest pear fruit. The results showed that H. sinensis could effectively control postharvest blue mold decay, significantly reducing both the decay rate and lesion diameter in pear fruits and the PAT content in pear wounds. In addition, H. sinensis treatment had no negative impression on pear storage. H. sinensis was shown to have a better ability to adapt to the environment, occupy space, and utilize nutrients than pathogens, which provides favorable conditions for H. sinensis to colonize the wound and surface of pear fruit. The inhibitory effect of H. sinensis on PAT represents a new solution to control PAT contamination in food.

Comparative physiological and transcriptomic analysis reveals an improved biological control efficacy of Sporidiobolus pararoseus Y16 enhanced with ascorbic acid against the oxidative stress tolerance caused by Penicillium expansum in pears

Sporidiobolus pararoseus Y16, a species of significant ecological importance, has distinctive physiological and biological regulatory systems that aid in its survival and environmental adaptation. The goal of this investigation was to understand the complex interactions between physiological and molecular mechanisms in pear fruits as induced by S. pararoseus Y16. The study investigated the use of S. pararoseus Y16 and ascorbic acid (VC) in combination in controlling blue mold decay in pears via physiological and transcriptomic approach. The study results showed that treatment of S. pararoseus Y16 with 150 μg/mL VC reduced pears blue mold disease incidence from 43% to 11%. Furthermore, the combination of S. pararoseus Y16 and VC significantly inhibited mycelia growth and spore germination of Penicillium expansum in the pear's wounds. The pre-treatment did not impair post-harvest qualities of pear fruit but increased antioxidant enzyme activity specifically polyphenol oxidase (PPO), peroxidase (POD), catalase (CAT) activities as well as phenylalanine ammonia-lyase (PAL) enzyme activity. The transcriptome analysis further uncovered 395 differentially expressed genes (DEGs) and pathways involved in defense mechanisms and disease resistance. Notable pathways of the DEGs include plant-pathogen interaction, tyrosine metabolism, and hormone signal transduction pathways. The integrative approach with both physiological and transcriptomic tools to investigate postharvest pathology in pear fruits with clarification on how S. pararoseus Y16 enhanced with VC, improved gene expression for disease defense, and create alternative controls strategies for managing postharvest diseases.

Effects of chitosan combined with microbes on blue mold of apples

Investigation on the inhibitory effect of chitosan combined with antagonistic bacteria on pathogenic fungi, at different concentrations on Penicillium expansum were studied in vitro and in vivo with Japanese Red Fuji apples. The chitosan solution with the concentration of 2% had the strongest resistance to Penicillium expansum and blue mold decay without affecting the growth of Bacillus amyloliquefaciens BA-16-8. Both the bacterial suspension and cell-free fermentation liquor of Bacillus amyloliquefaciens BA-16-8 could inhibit Penicillium expansum, and the former is superior to the latter in effect. Bacillus amyloliquefaciens BA-16-8 combined with chitosan can inhibit the activity and toxin-producing ability of Penicillium expansum. Bangladesh J. Bot. 53(1): 25-32, 2024 (March)

Chitosan inhibits Penicillium expansum possibly by binding to DNA and triggering apoptosis

Chitosan is a natural polysaccharide that is abundant, biocompatible and exhibits effective antifungal activity against various pathogenic fungi. However, the potential intracellular targets of chitosan in pathogenic fungi and the way of activity of chitosan are far from well known. The present work demonstrated that chitosan could inhibit Penicillium expansum, the principal causal agent of postharvest blue mold decay on apple fruits, by binding to DNA and triggering apoptosis. UV–visible spectroscopy, fluorescence spectroscopy and electrophoretic mobility assay proved the interaction between chitosan and DNA, while atomic force microscope (AFM) observation revealed the binding morphology of chitosan to DNA. Chitosan could inhibit in vitro DNA replication, and cell cycle analysis employing flow cytometry demonstrated that cell cycle was retarded by chitosan treatment. Furthermore, the reactive oxygen species (ROS) assay and membrane potential analysis showed that apoptosis was induced in P. expansum cells after exposure to chitosan. In conclusion, our results confirmed that chitosan interacts with DNA and induces apoptosis. These findings are expected to provide a feasible theoretical basis and practical direction for the promoting and implementing of chitosan in plant protection and further illuminate the possible antifungal mechanisms of chitosan against fungal pathogens.

Assay for transposase accessible-chromatin with high throughput sequencing (ATAC-seq) analysis the molecular responses of postharvest pear during Penicillium expansum infection

Blue mold decay caused by Penicillium expansum is a global destructive postharvest disease, which has brought huge economic losses to the pear industry. Transcription factors play an important role in pear anti-infection defense, and it has been observed that they have multiple functions. However, the roles of numerous TFs in the defense of pear against P. expansum have not been adequately explored. In this study, ATAC-seq was used to screen the TFs of pear against P. expansum, thereby understanding the chromatin-mediated gene regulation in the defense of pear against infection. The peak of differential expression enriched 9 transcription factors (AGL27, AT5G02460, AT2G28810, AT5G66940, AT3G46070 and OBP1, TCP3, BPC1 and TCP17). The up-regulated genes in our study were implicated in the MAPK signaling pathway-plant, plant hormone signal transduction pathway, plant-pathogen interaction pathway, glutathione metabolism pathway, phenylpropanoid biosynthesis, flavonoid biosynthesis pathway and carotenoid biosynthesis pathway were identified. Especially the transcription factors TGA, gene SAUR and CYCD3 in plant hormone signal transduction pathway and NCED, CYP707A in carotenoid biosynthesis pathway were differentially regulated. RT-qPCR analysis of twelve randomly selected differentially expressed peak-related genes confirmed the accuracy of ATAC-seq analysis of P. expansum infected pear.

Avirulent Isolates of Penicillium chrysogenum to Control the Blue Mold of Apple Caused by P. expansum.

Blue mold is an economically significant postharvest disease of pome fruit that is primarily caused by Penicillium expansum. To manage this disease and sustain product quality, novel decay intervention strategies are needed that also maintain long-term efficacy. Biocontrol organisms and natural products are promising tools for managing postharvest diseases. Here, two Penicillium chrysogenum isolates, 404 and 413, were investigated as potential biocontrol agents against P. expansum in apple. Notably, 404 and 413 were non-pathogenic in apple, yet they grew vigorously in vitro when compared to the highly aggressive P. expansum R19 and Pe21 isolates. Whole-genome sequencing and species-specific barcoding identified both strains as P. chrysogenum. Each P. chrysogenum strain was inoculated in apple with the subsequent co-inoculation of R19 or Pe21 simultaneously, 3, or 7 days after prior inoculation with 404 or 413. The co-inoculation of these isolates showed reduced decay incidence and severity, with the most significant reduction from the longer establishment of P. chrysogenum. In vitro growth showed no antagonism between species, further suggesting competitive niche colonization as the mode of action for decay reduction. Both P. chrysogenum isolates had incomplete patulin gene clusters but tolerated patulin treatment. Finally, hygromycin resistance was observed for both P. chrysogenum isolates, yet they are not multiresistant to apple postharvest fungicides. Overall, we demonstrate the translative potential of P. chrysogenum to serve as an effective biocontrol agent against blue mold decay in apples, pending practical optimization and formulation.

Transcriptome analysis provides insights into potential mechanisms of epsilon-poly-L-lysine inhibiting Penicillium expansum invading apples

Penicillium expansum (P. expansum) is a harmful pathogenic mold responsible for huge postharvest losses in apples. Epsilon‐poly‐L‐lysine (ε-PL) is a non-toxic antiseptic peptide derived from Streptomyces albulus. Many food preservative strategies use ε-PL to suppress foodborne pathogens in condiments, cakes, fruit and vegetable juices. In the present research, ε-PL’s inhibitory effects against P. expansum in vitro and in apples were investigated. The molecular mechanisms of ε-PL inhibiting P. expansum in apples were investigated by transcriptome analysis. Results showed that doses of 600 mg L−1 of ε-PL could prevent the development of P. expansum in vitro and control blue mold decay in apples. Plausible mechanisms of ε-PL against P. expansum in apples include: (i) reduction of antioxidant potential, including decreasing the expression of genes encoding superoxide dismutase (SOD), catalase (CAT), glutathione s-transferase (GST), xanthine dehydrogenase (XDH), D-amino-acid oxidase (DAO), weakening ROS scavenging ability of P. expansum cells and causing oxidative damage to cell, (ii) weakening its virulence towards apples, including reducing the expression of genes coding for cell wall degrading enzymes (CWDEs) such as pectinase and cellulase, (iii) disrupting mitochondrial function of P. expansum, including reducing expression of several rate-limiting enzyme coding genes of energy metabolic pathways such as EMP, TCA cycle and oxidative phosphorylation, which interfered with the cells’ energy metabolism, leading to insufficient ATP synthesis, weakening P. expansum’s resistance to external stress, and finally slowing down the invasion process into apples, (ⅳ) damaging the membrane integrity of P. expansum, including reducing the expression of genes encoding diaphragm wall degradation enzymes, cytomembrane lipid and ergosterol synthetase, multi-drug transporter, and inhibiting the differentiation of conidia.

Transcriptome analysis reveals mechanisms of the disease resistance in postharvest kiwifruit induced by Meyerozyma caribbica

Meyerozyma caribbica, an antagonistic yeast, effectively controls the postharvest blue mold decay of kiwifruit. Our previous study explored the mechanism of M. caribbica inhibiting the postharvest blue mold in kiwifruit at the physiological level, but its molecular mechanism is still unknown. This study investigated the related molecular mechanisms of disease-resistance in kiwifruits induced by M. caribbica based on transcriptome analysis. In addition, the effects of M. caribbica on the natural decay and storage quality of postharvest kiwifruit were investigated. The research showed that M. caribbica could reduce natural decay during kiwifruit storage without an apparent adverse effect on quality. The transcriptome analysis of postharvest kiwifruit found that there were 2916 DEGs, of which 1986 were up-regulated and 930 were down-regulated. KEGG pathway analysis showed that the plant-pathogen interaction pathway, glycolysis/gluconeogenesis pathway, flavonoid biosynthesis pathway, glutathione metabolism pathway and phenylpropane biosynthesis pathway were associated with the enhancement of kiwifruit resistance. The analysis of related metabolic pathways and functional analysis of related DEGs showed that M. caribbica could improve the expression of genes related to kiwifruit resistance, which are associated with induction of fruit resistance, mediated substance transport, improvement of cell wall strength, enhancement of plant antioxidant capacity, signal transduction and secondary metabolite synthesis, etc. These results provide a reference for future research on the use of antagonistic yeasts to prevent and control postharvest diseases of fruits and vegetables, and provide a theoretical basis for the practical application of antagonistic yeasts.

TMT-Based Proteomic Analysis of Hannaella sinensis-Induced Apple Resistance-Related Proteins.

Studies on the molecular mechanism of antagonistic yeasts to control apple postharvest diseases are not comprehensive enough. Our preliminary investigations screened the biocontrol effect of Hannaella sinensis, an antagonistic yeast, and discovered its control efficacy on apple blue mold decay. However, the molecular mechanism of H. sinensis-induced resistance in apple has not been studied. In this study, proteins from apple treated with H. sinensis and sterile saline were analyzed using TMT proteomics technology. It was found that H. sinensis treatment induced the expressions of apple resistance-related proteins. Among the proteins in H. sinensis-induced apple, proteins related to plant defense mechanisms, such as reactive oxygen species scavenging, improvement of plant resistance and synthesis of resistant substances, improvement of plant disease resistance, the degradation of the pathogen cell wall, cell signaling, antibacterial activity, transport of defense-related substances, and protein processing, were differentially regulated. The results of this study revealed the underlying molecular mechanisms of H. sinensis-induced apple resistance at the protein level; the results also provided a theoretical basis for the commercial application of H. sinensis.

Transcriptomic analyses reveal robust changes in the defense response of apples induced by Hannaella sinensis

Research on yeast antagonists has recently demonstrated their safety and efficacy in effectively preventing apple postharvest infections. Our previous study has revealed that the antagonistic yeast Hannaella sinensis has shown control activity against blue mold decay in apples caused by Penicillium expansum. However, the molecular networks underlying H. sinensis-treated apple's disease control mechanisms are not explored. Hence, we aimed to uncover the molecular changes of apples treated with H. sinensis based on transcriptomic analysis. Differentially expressed genes of apples treated with H. sinensis were identified through RNA-seq (152 up-regulated and 1480 down-regulated DEGs) and bioinformatic analysis. Among the DEGs, significant numbers were annotated into apple defense-related pathways, such as plant-pathogen interaction, plant hormone signal transduction, phenylpropanoid biosynthesis, tyrosine metabolism, glycerolipid metabolism, and alpha-linoleic acid pathways related to resistance regulation. Our results indicated that H. sinensis could induce disease resistance in apples, which leads to increased protection against postharvest pathogens. The current study paves the way for further understanding the biocontrol mechanism of antagonistic yeast against postharvest infections by enhancing host defense.

Would You Like Wood or Plastic? Bin Material, Sanitation Treatments, and Bin Inoculum Levels Impact Blue Mold Decay of Stored Apple Fruit.

Blue mold, caused primarily by Penicillium expansum, is a significant postharvest disease of apples. It not only causes economic losses but also produces mycotoxins that contaminate processed fruit products, which contributes to food waste and loss. Previous research has shown that packing and storage bins harbor Penicillium spores and that steam and hot water efficiently reduce spore inoculum levels. However, studies using wooden and plastic bins regarding their ability to harbor spores, the effect of chemical sanitation treatments on spore levels, and the impact of rinsate from treated bins on apple fruit decay have not been investigated for the Mid-Atlantic area (Okull et al. 2006; Rosenberger 2009). We evaluated different sanitation treatments (chemical and physical) to reduce P. expansum inoculum levels on wooden and plastic bins. We determined that wooden bins bound P. expansum spores four orders of magnitude higher than plastic. When both bin types were treated with steam (wooden) or sterile hot water (plastic), Thyme Guard, or Academy, all treatments resulted in significantly (P < 0.05) lower spore levels compared to untreated controls. Although, plastic bins retained lower numbers of spores after inoculation with contaminated spore rinsate and required much higher concentrations of P. expansum spores in rinsate to retain spores at levels that would lead to decay on apple fruit. Overall, we demonstrated that plastic bins retain fewer spores than wooden bins and that both can be sanitized by various physical or chemical treatments. We envision that our findings will be applicable in the future as the techniques implemented in this study were used to investigate industry-relevant questions. Our goal is that the research techniques and findings become feasible with advancements in technology and/or accompany other shifts in existing processes in commercial pome fruit packing and storage facilities.

Screening of antagonistic yeast strains for postharvest control of Penicillium expansum causing blue mold decay in table grape

Blue mold decay caused by Penicillium expansum is one of the most important postharvest diseases of grapes, leading to considerable economic losses. Regarding the increasing demand for pesticide-free foods, this study aimed to find potential yeast strains for biological control of blue mold on table grapes. A total of 50 yeast strains were screened for antagonistic activity against P. expansum using the dual culture method and six strains significantly inhibited the fungal growth. All six yeast strains (Coniochaeta euphorbiae, Auerobasidium mangrovei, Tranzscheliella sp., Geotrichum candidum, Basidioascus persicus, and Cryptococcus podzolicus) reduced the fungal growth (29.6–85.0%) and the decay degree of wounded grape berries inoculated with P. expansum while G. candidum was found to be the most efficient biocontrol agent. On the basis of antagonistic activity, the strains were further characterized by in vitro assays involving inhibition of conidial germination, production of volatile compounds, iron competition, production of hydrolytic enzymes, biofilm-forming capacity, and exhibited three or more putative mechanisms. To our knowledge, the yeasts are reported for the first time as potential biocontrol agents against the blue mold of grapes but more study is required to evaluate their efficiency related to field application.

Transcriptome Analysis and Functional Characterization Reveal That Peclg Gene Contributes to the Virulence of Penicillium expansum on Apple Fruits.

Penicillium expansum is the causal agent of blue mold decay on apple fruits and is also known to be the major producer of patulin, a mycotoxin that represents serious hazard to human health. Several mechanisms have been suggested to explain the pathogenesis of P. expansum in host plants. Secreted effector proteins are vital for the pathogenicity of many fungal pathogens through manipulating their hosts for efficient colonization. In this study, we performed a RNA-Seq analysis followed by computational prediction of effector proteins from P. expansum during infection of the host apple fruits, and a total of 212 and 268 candidate effector protein genes were identified at 6 and 9 h after inoculation (hai), respectively. One of the candidate effector protein genes was identified as a concanavalin A-like lectin/glucanase (Peclg), which was dramatically induced during the pathogen-host interaction. Targeted knockout of Peclg resulted in significant reduction in conidial production and germination relative to the wild type. Further studies showed that in addition to salt stress, the mutant was much more sensitive to SDS and Congo red, suggesting a defect in cell wall integrity. Pathogenicity assays revealed that the ΔPeclg mutant showed significant decrease in virulence and infectious growth on apple fruits. All these results suggest that Peclg is required for fungal growth, stress response, and the virulence of P. expansum.

Alterations in the proteome as a regulating mechanism for patulin stress by the antagonistic yeast Meyerozyma guilliermondii

Meyerozyma guilliermondii is an antagonistic yeast; our research team has recently reported its biocontrol activities against blue mold decay of pears and strong patulin (PAT) reduction ability in vitro. PAT is a harmful mycotoxin produced by some species of Penicillium, Aspergillus, and Byssochlamys. The PAT degradation process and molecular mechanism(s) of M. guilliermondii remain unclear. The data-independent acquisition (DIA) strategies promise a comprehensive, reproducible, digital, qualitative and quantitative record of the proteins present in a sample. Differentially expressed proteins accompanying PAT degradation in M. guilliermondii were observed to investigate PAT reduction mechanisms. The comparative proteomic analysis of M. guilliermondii showed that 136 proteins were up-regulated and 122 were down-regulated upon PAT degradation. The M. guilliermondii's regulation of PAT response mainly includes the up-regulation of (1) growth and reproduction-related protein expression, (2) transcription and translation-related protein expression, (3) resistance-related protein expression, (4) multidrug transporters, (5) anti-oxidative stress-related proteins, (6) the cell wall and cell membrane production-related proteins, and (7) PAT degradation-related protein expression. This paper analyzed M. guilliermondii’s molecular response and regulation upon PAT reduction at the gene and protein expression levels. Our results provide a solid foundation for PAT control in fruits and their products by antagonistic yeasts.

Postharvest methyl jasmonate treatment inhibits blue mold decay in Ginkgo biloba seeds by inducing antioxidant and defense systems

Postharvest methyl jasmonate treatment inhibits blue mold decay in Ginkgo biloba seeds by inducing antioxidant and defense systems

Study on the effect of Debaryomyces hansenii enhanced by alginate oligosaccharide against postharvest blue mold decay of apples and the physiological mechanisms involved

Blue mold decay is the most common disease during postharvest storage of apples caused by Penicillium expansum, leading to huge economic losses to the apple industry. Antagonistic yeasts are widely used in biological control, and organic compounds can be used as elicitors to induce antagonistic yeasts to further improve their biocontrol effect. In this study, we assessed the biocontrol efficacy of the antagonistic yeast, Debaryomyces hansenii, enhanced by alginate oligosaccharide (AOS) in controlling the postharvest decay of apples and studied the possible physiological mechanisms involved in this process. The results of this study were as follows: (1) AOS enhanced the biocontrol ability of D. hansenii against P. expansum infestation of apples. In the in vivo experiments, D. hansenii induced by 0.5% AOS significantly reduced the disease incidence and lesion diameter in apples, demonstrating good control of blue mold. When treated with D. hansenii-induced with AOS, the disease incidence rate of apples was only 21.6%, while that of yeast alone was 37.5%. (2) In the in vitro experiments, AOS significantly improved the inhibitory effect of D. hansenii on the germination rate, germ tube length, and colony diameter of P. expansum. The results suggested that AOS-induced yeast exhibited a certain inhibitory effect on the growth of P. expansum. (3) The activities of diseases resistance-related enzymes of apples treated with AOS-induced D. hansenii such as polyphenol oxidase (PPO), peroxidase (POD), and phenylalanine ammonia-lyase (PAL) were increased compared to the yeast alone and the control group. Apart from that, the content of substances such as total phenols and flavonoids maintained the original level. These results suggest that the resistance of apples against pathogenic fungi may be improved by increasing the activities of disease resistance related enzymes activities of the fruit. In summary, the method of enhancing antagonistic yeast by AOS is very promising and efficient for improving biological control to reduce economic losses in the apple industry.

Study on the biocontrol effect and physiological mechanism of Hannaella sinensis on the blue mold decay of apples

Blue mold decay is a major postharvest disease of apples, causing considerable losses to the apple industry. In the early stage of this research, an antagonistic yeast, Hannaella sinensis, with a good control effect on the blue mold of apples, was selected. On this basis, the main purpose of this work was to study the biocontrol effect of H. sinensis on the blue mold of apples and the mechanisms involved. The results showed that H. sinensis could effectively control the blue mold decay of apples, reduce the rot rate and diameter, and the antagonistic effect strengthened with the increase of H. sinensis concentration (1 × 108 cells/mL). Further in vitro experiments proved that H. sinensis could significantly inhibit the spore germination and germ tube length of P. expansum. In addition, stable colonization of H. sinensis on apple wounds and surfaces confirmed the environmental adaptability and the ability to compete with other microbiota for nutrition and space. Moreover, H. sinensis induced the activities of resistance-related enzymes such as polyphenol oxidase (PPO), peroxidase (POD), ascorbate peroxidase (APX), superoxide dismutase (SOD), and phenylalanine ammonia-lyase (PAL) in apples and the content of the coding genes corresponding to these enzymes was also higher than that of the control group. Our results indicate that H. sinensis treatment could induce the disease resistance of apples. In summary, H. sinensis served as a promising antagonistic yeast for the prevention and treatment of postharvest blue mold decay of apples.

Integrated transcriptomic and metabonomic analysis reveal mechanisms of disease resistance in apples induced by Wickerhamomyces anomalus

The antagonistic yeast Wickerhamomyces anomalus was reported to have a biocontrol efficacy against blue mold decay of apples, and possible physiological biocontrol mechanisms were investigated in our previous research. However, the molecular mechanisms related to the resistance response were unclear. In this study, the related molecular mechanisms of disease-resistance in apples induced by W. anomalus based on transcriptomic and metabonomic analysis were investigated. The results of the transcriptome data showed that W. anomalus induced the up-regulation of genes related to resistance, plant signal transduction, genes involved in regulating the synthesis of resistance related substances, and genes related to antioxidant and stress resistance. Integrated transcriptomic and metabonomic analysis indicated that multiple genes involved in the phenylpropane biosynthesis pathway, ubiquinone and other terpenoid-quinone biosynthesis pathway and phenylalanine metabolism pathway were up-regulated, and the contents of corresponding metabolites were also increased, so as to improve the disease resistance of apple fruit.

Characterization and Functional Analysis of a New Calcium/Calmodulin-Dependent Protein Kinase (CaMK1) in the Citrus Pathogenic Fungus Penicillium italicum.

Calcium (Ca2+)/calmodulin-dependent protein kinases (CaMKs) act as a class of crucial elements in Ca2+-signal transduction pathways that regulate fungal growth, sporulation, virulence, and environmental stress tolerance. However, little is known about the function of such protein kinase in phytopathogenic Penicillium species. In the present study, a new CaMK gene from the citrus pathogenic fungus P. italicum, designated PiCaMK1, was cloned and functionally characterized by gene knockout and transcriptome analysis. The open reading frame of PiCaMK1 is 1209 bp in full length, which encodes 402 amino acid residues (putative molecular weight ~45.2 KD) with the highest homologous (~96.3%) to the P. expansum CaMK. The knockout mutant ΔPiCaMK1 showed a significant reduction in vegetative growth, conidiation, and virulence (i.e., to induce blue mold decay on citrus fruit). ΔPiCaMK1 was less sensitive to NaCl- or KCl-induced salinity stress and less resistant to mannitol-induced osmotic stress, indicating the functional involvement of PiCaMK1 in such environmental stress tolerance. In contrast, the PiCaMK1-complemented strain ΔPiCaMK1COM can restore all the defective phenotypes. Transcriptome analysis revealed that knockout of PiCaMK1 down-regulated expression of the genes involved in DNA replication and repair, cell cycle, meiosis, pyrimidine and purine metabolisms, and MAPK signaling pathway. Our results suggested the critical role of PiCaMK1 in regulating multiple physical and cellular processes of citrus postharvest pathogen P. italicum, including growth, conidiation, virulence, and environmental stress tolerance.

The necrosis-inducing protein (NIP) gene contributes to Penicillium expansum virulence during postharvest pear infection

Penicillium expansum is the causative fungus of blue mold decay in postharvest pears resulting in substantial economic losses. Investigating P. expansum-pear fruit interactions is necessary to help develop P. expansum control strategies for effective and safe pear production. Investigating the P. expansum gene expression alterations and essential gene functions during the infection process is indispensable. Based on our results, the necrosis-inducing protein (NIP) gene was closely associated with genes related to plant cell wall degrading enzymes (CWDEs) and involved in P. expansum virulence. The NIP has high homology with other already-known fungal NIPs. To evidence the role of NIP in P. expansum virulence, NIP mutant (including knockout (ΔNIP) and complementation mutant (cNIP)) P. expansum were generated. Despite the NIP deletion did not affect the basic morphology and structure of P. expansum, it slowed down the fungal growth and hyphal production, thus reducing P. expansum's sporulation and patulin (PAT) accumulation. Furthermore, the deletion of NIP reduced the pathogenicity of P. expansum in pear. The complementation of NIP (cNIP) restored the growth, conidia production, PAT accumulation, and virulence of ΔNIP to the level of wild-type P. expansum. In addition, PAT can cause decay and aggravate the disease severity of wild-type P. expansum and ΔNIP on pears. Our results confirmed NIP plays a crucial role in P. expansum's growth, hyphal production, and pathogenicity in pears.