Functional analysis of two sterol regulatory element binding proteins in Penicillium digitatum

Transcriptome Analysis Reveals Potential Regulators of DMI Fungicide Resistance in the Citrus Postharvest Pathogen Penicillium digitatum

Green mold, caused by Penicillium digitatum, is the major cause of citrus postharvest decay. Currently, the application of sterol demethylation inhibitor (DMI) fungicide is one of the main control measures to prevent green mold. However, the fungicide-resistance problem in the pathogen P. digitatum is growing. The regulatory mechanism of DMI fungicide resistance in P. digitatum is poorly understood. Here, we first performed transcriptomic analysis of the P. digitatum strain Pdw03 treated with imazalil (IMZ) for 2 and 12 h. A total of 1338 genes were up-regulated and 1635 were down-regulated under IMZ treatment for 2 h compared to control while 1700 were up-regulated and 1661 down-regulated under IMZ treatment for 12 h. The expression of about half of the genes in the ergosterol biosynthesis pathway was affected during IMZ stress. Further analysis identified that 84 of 320 transcription factors (TFs) were differentially expressed at both conditions, making them potential regulators in DMI resistance. To confirm their roles, three differentially expressed TFs were selected to generate disruption mutants using the CRISPR/Cas9 technology. The results showed that two of them had no response to IMZ stress while ∆PdflbC was more sensitive compared with the wild type. However, disruption of PdflbC did not affect the ergosterol content. The defect in IMZ sensitivity of ∆PdflbC was restored by genetic complementation of the mutant with a functional copy of PdflbC. Taken together, our results offer a rich source of information to identify novel regulators in DMI resistance.

Transcriptome Analysis of mfs2-Defective Penicillium digitatum Mutant to Reveal Importance of Pdmfs2 in Developing Fungal Prochloraz Resistance

Demethylation inhibitors (DMIs), including prochloraz, are popular fungicides to control citrus postharvest pathogens such as Penicillium digitatum (green mold). However, many P. digitatum strains have developed prochloraz resistance, which decreases drug efficacy. Specific major facilitator superfamily (MFS) transporter gene mfs2, encoding drug-efflux pump protein MFS2, has been identified in P. digitatum strain F6 (PdF6) to confer fungal strain prochloraz resistance. However, except for the drug-efflux pump function of MFS2, other mechanisms relating to the Pdmfs2 are not fully clear. The present study reported a transcriptome investigation on the mfs2-defective P. digitatum strain. Comparing to the wild-type strain, the mfs2-defective strain showed 717 differentially expressed genes (DEGs) without prochloraz induction, and 1221 DEGs with prochloraz induction. The obtained DEGs included multiple isoforms of MFS transporter-encoding genes, ATP-binding cassette (ABC) transporter-encoding genes, and multidrug and toxic compound extrusion (MATE) family protein-encoding genes. Many of these putative drug-efflux pump protein-encoding genes had significantly lower transcript abundances in the mfs2-defective P. digitatum strain at prochloraz induction, as compared to the wild-type strain, including twenty-two MFS transporter-encoding genes (MFS1 to MFS22), two ABC transporter-encoding genes (ABC1 and ABC2), and three MATE protein-encoding genes (MATE1 to MATE3). The prochloraz induction on special drug-efflux pump protein genes in the wild-type strain was not observed in the mfs2-defective strain, including MFS21, MFS22, ABC2, MATE1, MATE2, and MATE3. On the other hand, the up-regulation of other drug-efflux pump protein genes in the mfs2-defective strain cannot recover the fungal prochloraz resistance, including MFS23, MFS26, MFS27, MFS31, MFS33, and ABC3 to ABC8. The functional enrichment of DEGs based on Kyoto Encyclopedia of Genes and Genomes (KEGG), Clusters of Orthologous Groups (COG), and euKaryotic Orthologous Groups (KOG) database resources suggested some essential contributors to the mfs2-relating prochloraz resistance, including ribosome biosynthesis-related genes, oxidative phosphorylation genes, steroid biosynthesis-related genes, fatty acid and lipid metabolism-related genes, and carbon- and nitrogen-metabolism-related genes. The results indicated that the MFS2 transporter might be involved in the regulation of multiple drug-efflux pump protein gene expressions and multiple metabolism-related gene expressions, thus playing an important role in developing P. digitatum prochloraz resistance.

Elicitation of Fruit Fungi Infection and Its Protective Response to Improve the Postharvest Quality of Fruits

Fruit diseases brought on by fungus infestation leads to postharvest losses of fresh fruit. Approximately 30% of harvested fruits do not reach consumers’ plates due to postharvest losses. Fungal pathogens play a substantial part in those losses, as they cause the majority of fruit rots and consumer complaints. Understanding fungal pathogenic processes and control measures is crucial for developing disease prevention and treatment strategies. In this review, we covered the presented pathogen entry, environmental conditions for pathogenesis, fruit’s response to pathogen attack, molecular mechanisms by which fungi infect fruits in the postharvest phase, production of mycotoxin, virulence factors, fungal genes involved in pathogenesis, and recent strategies for protecting fruit from fungal attack. Then, in order to investigate new avenues for ensuring fruit production, existing fungal management strategies were then assessed based on their mechanisms for altering the infection process. The goal of this review is to bridge the knowledge gap between the mechanisms of fungal disease progression and numerous disease control strategies being developed for fruit farming.

Antifungal mechanism of (E)-2-hexenal against Botrytis cinerea growth revealed by transcriptome analysis

Gray mold caused by Botrytis cinerea, a necrotrophic plant pathogen, is one of the most damaging diseases of tomato, resulting in both pre- and post-harvest losses. (E)-2-Hexenal dose-dependently inhibited the mycelial growth of B. cinerea, and caused distortion of mycelia and loss of the cytoplasm content, thus altering the morphology of B. cinerea hyphae. To understand molecular processes in response to (E)-2-hexenal, transcriptome sequencing was carried out using RNA-Seq technology. RNA-Seq results revealed that a total of 3,893 genes were differentially expressed in B. cinerea samples treated with (E)-2-hexenal fumigation. Among these genes, 1,949 were upregulated and 1,944 were downregulated. Moreover, further analysis results showed 2,113 unigenes were mapped onto 259 pathways in Kyoto Encyclopedia of Genes and Genomes (KEGG). Moreover, (E)-2-hexenal stress affected the expression of genes involved in the pathways of cell wall, cell membrane, and energy metabolism. KEGG pathway analysis showed that the terpenoid backbone biosynthesis and steroid biosynthesis were the most enriched in ergosterol biosynthetic process transcriptome data. Particularly, (E)-2-hexenal fumigation had influenced ergosterol biosynthetic gene expression levels (e.g., ERG1, ERG3, ERG4, ERG7, ERG12, ERG13, ERG24, ERG25, ERG26, and ERG27), which were in good agreement with the experimental measurement results, and the ergosterol content decreased. Collectively, the results of this study increase our current understanding of (E)-2-hexenal inhibition mechanisms in B. cinerea and provide relevant information on postharvest shelf life extension and preservation of fruits and vegetables.

Deciphering Molecular Determinants Underlying Penicillium digitatum's Response to Biological and Chemical Antifungal Agents by Tandem Mass Tag (TMT)-Based High-Resolution LC-MS/MS

Penicillium digitatum is a widespread pathogen responsible for the postharvest decay of citrus, one of the most economically important crops worldwide. Currently, chemical fungicides are still the main strategy to control the green mould disease caused by the fungus. However, the increasing selection and proliferation of fungicide-resistant strains require more efforts to explore new alternatives acting via new or unexplored mechanisms for postharvest disease management. To date, several non-chemical compounds have been investigated for the control of fungal pathogens. In this scenario, understanding the molecular determinants underlying P. digitatum's response to biological and chemical antifungals may help in the development of safer and more effective non-chemical control methods. In this work, a proteomic approach based on isobaric labelling and a nanoLC tandem mass spectrometry approach was used to investigate molecular changes associated with P. digitatum's response to treatments with α-sarcin and beetin 27 (BE27), two proteins endowed with antifungal activity. The outcomes of treatments with these biological agents were then compared with those triggered by the commonly used chemical fungicide thiabendazole (TBZ). Our results showed that differentially expressed proteins mainly include cell wall-degrading enzymes, proteins involved in stress response, antioxidant and detoxification mechanisms and metabolic processes such as thiamine biosynthesis. Interestingly, specific modulations in response to protein toxins treatments were observed for a subset of proteins. Deciphering the inhibitory mechanisms of biofungicides and chemical compounds, together with understanding their effects on the fungal physiology, will provide a new direction for improving the efficacy of novel antifungal formulations and developing new control strategies.

Unveiling the Role Displayed by Penicillium digitatum PdMut3 Transcription Factor in Pathogen-Fruit Interaction

Zn2Cys6 transcription factors are unique to fungi and are involved in different regulatory functions. In this study, we have identified the Penicillium digitatumPdMut3 gene, which encodes a putative Zn (II) 2Cys6 DNA-binding protein. Elimination of PdMut3 in Pd1 strain caused increased virulence during citrus infection. The transcription of the PdMut3 gene showed a higher expression rate during fungal growth and less transcription during fruit infection. Furthermore, the deletion of the gene in the wild-type isolate of P. digitatum did not produce any modification of the sensitivity to different fungicides, indicating that the gene is not associated with resistance to fungicides. In contrast, PdMut3 null mutants showed a reduction in growth in minimal media, which was associated with severe alterations in conidiophore development and morphological alterations of the hyphae. Mutants showed greater sensitivity to compounds that interfere with the cell wall and an invasive growth block. Thus, PdMut3 might have an indirect role in fungi virulence through metabolism and peroxisomes development.

Molecular Mechanisms Underlying Fungicide Resistance in Citrus Postharvest Green Mold

The necrotrophic fungus Penicillium digitatum (Pd) is responsible for the green mold disease that occurs during postharvest of citrus and causes enormous economic losses around the world. Fungicides remain the main method used to control postharvest green mold in citrus fruit storage despite numerous occurrences of resistance to them. Hence, it is necessary to find new and more effective strategies to control this type of disease. This involves delving into the molecular mechanisms underlying the appearance of resistance to fungicides during the plant–pathogen interaction. Although mechanisms involved in resistance to fungicides have been studied for many years, there have now been great advances in the molecular aspects that drive fungicide resistance, which facilitates the design of new means to control green mold. A wide review allows the mechanisms underlying fungicide resistance in Pd to be unveiled, taking into account not only the chemical nature of the compounds and their target of action but also the general mechanism that could contribute to resistance to others compounds to generate what we call multidrug resistance (MDR) phenotypes. In this context, fungal transporters seem to play a relevant role, and their mode of action may be controlled along with other processes of interest, such as oxidative stress and fungal pathogenicity. Thus, the mechanisms for acquisition of resistance to fungicides seem to be part of a complex framework involving aspects of response to stress and processes of fungal virulence.

The completed genome sequence of the pathogenic ascomycete fungus Penicillium digitatum

P. digitatum, the causative agent of green mold, is one of the most destructive pathogens in the citrus industry. To facilitate basal researches on this important plant pathogen, here we report a finished genome sequence for P. digitatum strain PDW03 using a combination of Illumina, PacBio, and Hi-C sequencing technologies. The assembly comprised 6 chromosomes from telomere to telomere and encodes approximately 9000 proteins. Genomic re-analyses identified 302 Carbohydrate-active enzymes, 420 secreted proteins, and 39 secondary metabolite (SM) gene clusters. Furthermore, we found 10 fragmentary SM clusters in the P. digitatum PDW03 genome. Pangenome analysis based on 5 P. digitatum genomes available showed that conserved orthogroups account for ~68% of the species pangenome. Taken together, this fully completed P. digitatum genome will provide an optimum resource for further researches to investigate the driving forces of fungal host switch and effectors functioning in plant-pathogen interaction.

Protection of Citrus Fruits from Postharvest Infection with Penicillium digitatum and Degradation of Patulin by Biocontrol Yeast Clavispora lusitaniae 146

Fungal rots are one of the main causes of large economic losses and deterioration in the quality and nutrient composition of fruits during the postharvest stage. The yeast Clavispora lusitaniae 146 has previously been shown to efficiently protect lemons from green mold caused by Penicillium digitatum. In this work, the effect of yeast concentration and exposure time on biocontrol efficiency was assessed; the protection of various citrus fruits against P. digitatum by C. lusitaniae 146 was evaluated; the ability of strain 146 to degrade mycotoxin patulin was tested; and the effect of the treatment on the sensory properties of fruits was determined. An efficient protection of lemons was achieved after minimum exposure to a relatively low yeast cell concentration. Apart from lemons, the yeast prevented green mold in grapefruits, mandarins, oranges, and tangerines, implying that it can be used as a broad-range biocontrol agent in citrus. The ability to degrade patulin indicated that strain 146 may be suitable for the control of further Penicillium species. Yeast treatment did not alter the sensory perception of the aroma of fruits. These results corroborate the potential of C. lusitaniae 146 for the control of postharvest diseases of citrus fruits and indicate its suitability for industrial-scale fruit processing.

Genome-wide identification and functional analysis of the horizontally transferred genes in Penicillium

Horizontal gene transfer (HGT) is the transmission of genetic material between different evolutionary lineages and is believed to be an important source of genomic innovation in fungi. In this study, we searched for prokaryotic-derived HGTs in 23 fully sequenced genomes using a comprehensive phylogenomic pipeline followed by manual curation. We found strong support for 60 HGT events comprising 190 genes putatively acquired from bacteria. HGT affected all Penicillium species to various degrees. Gene duplication events happened to 3 HGT genes after the transmission. Most HGT events include genes encoding a variety of enzymes, which are associated with sugar, amino acid, and lipid metabolism. Transcriptome data from 6 Penicillium species revealed that 33 of 35 HGT genes showed expression under the conditions tested and 16 genes were differentially expressed. Our results suggest an important role for inter-domain gene transfers in shaping the genome of Penicillium fungi.

Crosstalk between sterol and neutral lipid metabolism in the alga Haematococcus pluvialis exposed to light stress

The presence, biosynthesis and functional role of sterols in the green microalga Haematococcus pluvialis remain poorly understood. In this work we studied the effect of high-light (HL) stress on sterol synthesis in H. pluvialis UTEX 2505 cells. HL stress induced the synthesis of sterols in parallel with that of triacylglycerides (TAG), giving rise to the synthesis of cholesterol over that of phytosterols. Blockage of the carotenogenic 1-deoxy-D-xylulose 5-phosphate (MEP) pathway is shown to be involved in HL-induced sterol synthesis. In addition, high irradiance exposure induced MEP- and fatty acid (FA)-biosynthetic transcripts. The pharmacological inhibition of these pathways suggests a possible feedback regulation of sterol and FA homeostasis. Finally, both lipid classes proved crucial to the adequate photosynthetic performance of H. pluvialis grown under HL intensity stress. Our findings reveal new insights into H. pluvialis lipid metabolism that contribute to the development of value-added bioproducts from microalgae.

Significance of 195 bp-enhancer of PdCYP51B in the acquisition of Penicillium digitatum DMI resistance and increase of fungal virulence

Two sterol 14α-demethylase genes from Penicillium digitatum, PdCYP51A and PdCYP51B, were evaluated and revealed that 95% of Imazalil (IMZ)-resistant isolates carried a 195-bp insertion in the PdCYP51B promoter. We functionally characterized both sterol 14α-demethylases by overexpression. Molecular analysis of overexpression mutants showed that the introduction of PdCYP51B insertion is more stable than the five-tandem repeat PdCYP51A sequence previously described that confers DMI fungicide resistance. The both enhancers can coexist in P. digitatum isolates that initially contained the 195-bp PdCYP51B insertion but the introduction of 195-bp PdCYP51B enhancer promoted the loss of the five-tandem repeat of PdCYP51A. The incorporation of 195-bp PdCYP51B resulted in an increase of DMI fungicide resistance in mutants from already resistant isolates and confers resistance to DMIs in mutants from sensitive isolates. Transcription evaluation of the both genes showed noticeable induction in all overexpression mutants, except for those coming from the five-tandem repeat PdCYP51A sequence, whereas PdCYP51A expression dropped dramatically. Only PdCYP51B exhibited up-regulation during citrus infection compared to axenic growth, and the role of PdCYP51B in fungal virulence was further reinforced since strains with low virulence showed increased infectivity in overexpression mutants. This study suggested the predominant role of the PdCYP51B enhancer in the acquisition of DMI resistance and fungal virulence, by replacing homologues genes with same putative function.

A 23 bp cyp51A Promoter Deletion Associated With Voriconazole Resistance in Clinical and Environmental Isolates of Neocosmospora keratoplastica

In the fungal pathogen Aspergillus fumigatus, resistance to azole antifungals is often linked to mutations in CYP51A, a gene that encodes the azole antifungal drug target lanosterol 14α-demethylase. The aim of this study was to investigate whether similar changes could be associated with azole resistance in a Malaysian Fusarium solani species complex (FSSC) isolate collection. Most (11 of 15) clinical FSSC isolates were Neocosmospora keratoplastica and the majority (6 of 10) of environmental isolates were Neocosmospora suttoniana strains. All 25 FSSC isolates had high minimum inhibitory concentrations (MICs) for itraconazole and posaconazole, low MICs for amphotericin B, and various (1 to >32 mg/l) voriconazole susceptibilities. There was a tight association between a 23 bp CYP51A promoter deletion and high (>32 mg/l) voriconazole MICs; of 19 FSSC strains sequenced, nine isolates had voriconazole MICs > 32 mg/l, and they all contained the 23 bp CYP51A promoter deletion, although it was absent in the ten remaining isolates with low (≤12 mg/l) voriconazole MICs. Surprisingly, this association between voriconazole resistance and the 23 bp CYP51A promoter deletion held true across species boundaries. It was randomly distributed within and across species boundaries and both types of FSSC isolates were found among environmental and clinical isolates. Three randomly selected N. keratoplastica isolates with low (≤8 mg/l) voriconazole MICs had significantly lower (1.3–7.5 times) CYP51A mRNA expression levels than three randomly selected N. keratoplastica isolates with high (>32 mg/l) voriconazole MICs. CYP51A expression levels, however, were equally strongly induced (~6,500-fold) by voriconazole in two representative strains reaching levels, after 80 min of induction, that were comparable to those of CYP51B. Our results suggest that FSSC isolates with high voriconazole MICs have a 23 bp CYP51A promoter deletion that provides a potentially useful marker for voriconazole resistance in FSSC isolates. Early detection of possible voriconazole resistance is critical for choosing the correct treatment option for patients with invasive fusariosis.

Citrus Postharvest Green Mold: Recent Advances in Fungal Pathogenicity and Fruit Resistance

As the major postharvest disease of citrus fruit, postharvest green mold is caused by the necrotrophic fungus Penicillium digitatum (Pd), which leads to huge economic losses worldwide. Fungicides are still the main method currently used to control postharvest green mold in citrus fruit storage. Investigating molecular mechanisms of plant-pathogen interactions, including pathogenicity and plant resistance, is crucial for developing novel and safer strategies for effectively controlling plant diseases. Despite fruit-pathogen interactions remaining relatively unexplored compared with well-studied leaf-pathogen interactions, progress has occurred in the citrus fruit-Pd interaction in recent years, mainly due to their genome sequencing and establishment or optimization of their genetic transformation systems. Recent advances in Pd pathogenicity on citrus fruit and fruit resistance against Pd infection are summarized in this review.

Transcriptome analysis of fungicide-responsive gene expression profiles in two Penicillium italicum strains with different response to the sterol demethylation inhibitor (DMI) fungicide prochloraz

Background

Penicillium italicum (blue mold) is one of citrus pathogens causing undesirable citrus fruit decay even at strictly-controlled low temperatures (< 10 °C) during shipping and storage. P. italicum isolates with considerably high resistance to sterol demethylation inhibitor (DMI) fungicides have emerged; however, mechanism(s) underlying such DMI-resistance remains unclear. In contrast to available elucidation on anti-DMI mechanism for P. digitatum (green mold), how P. italicum DMI-resistance develops has not yet been clarified.

Results

The present study prepared RNA-sequencing (RNA-seq) libraries for two P. italicum strains (highly resistant (Pi-R) versus highly sensitive (Pi-S) to DMI fungicides), with and without prochloraz treatment, to identify prochloraz-responsive genes facilitating DMI-resistance. After 6 h prochloraz-treatment, comparative transcriptome profiling showed more differentially expressed genes (DEGs) in Pi-R than Pi-S. Functional enrichments identified 15 DEGs in the prochloraz-induced Pi-R transcriptome, simultaneously up-regulated in P. italicum resistance. These included ATP-binding cassette (ABC) transporter-encoding genes, major facilitator superfamily (MFS) transporter-encoding genes, ergosterol (ERG) anabolism component genes ERG2, ERG6 and EGR11 (CYP51A), mitogen-activated protein kinase (MAPK) signaling-inducer genes Mkk1 and Hog1, and Ca²⁺/calmodulin-dependent kinase (CaMK) signaling-inducer genes CaMK1 and CaMK2. Fragments Per Kilobase per Million mapped reads (FPKM) analysis of Pi-R transcrtiptome showed that prochloraz induced mRNA increase of additional 4 unigenes, including the other two ERG11 isoforms CYP51B and CYP51C and the remaining kinase-encoding genes (i.e., Bck1 and Slt2) required for Slt2-MAPK signaling. The expression patterns of all the 19 prochloraz-responsive genes, obtained in our RNA-seq data sets, have been validated by quantitative real-time PCR (qRT-PCR). These lines of evidence in together draw a general portrait of anti-DMI mechanisms for P. italicum species. Intriguingly, some strategies adopted by the present Pi-R were not observed in the previously documented prochloraz-resistant P. digitatum transcrtiptomes. These included simultaneous induction of all major EGR11 isoforms (CYP51A/B/C), over-expression of ERG2 and ERG6 to modulate ergosterol anabolism, and concurrent mobilization of Slt2-MAPK and CaMK signaling processes to overcome fungicide-induced stresses.

Conclusions

The present findings provided transcriptomic evidence on P. italicum DMI-resistance mechanisms and revealed some diversity in anti-DMI strategies between P. italicum and P. digitatum species, contributing to our knowledge on P. italicum DMI-resistance mechanisms.

Sterol Regulatory Element-Binding Protein (Sre1) Promotes the Synthesis of Carotenoids and Sterols in Xanthophyllomyces dendrorhous

Xanthophyllomyces dendrorhous is a basidiomycete yeast that synthesizes carotenoids, mainly astaxanthin, which are of great commercial interest. Currently, there are many unknown aspects related to regulatory mechanisms on the synthesis of carotenoids in this yeast. Our recent studies showed that changes in sterol levels and composition resulted in upregulation of genes in the mevalonate pathway required for the synthesis of carotenoid precursors, leading to increased production of these pigments. Sterol Regulatory Element-Binding Proteins (SREBP), called Sre1 in yeast, are conserved transcriptional regulators of sterol homeostasis and other cellular processes. Given the results linking sterols and carotenoids, we investigated the role of SREBP in sterol and carotenoid synthesis in X. dendrorhous. In this study, we present the identification and functional characterization of the X. dendrorhous SRE1 gene, which encodes the transcription factor Sre1. The deduced protein has the characteristic features of SREBP/Sre1 and binds to consensus DNA sequences in vitro. RNA-seq analysis and chromatin-immunoprecipitation experiments showed that genes of the mevalonate pathway and ergosterol biosynthesis are directly regulated by Sre1. The sre1- mutation reduced sterol and carotenoid production in X. dendrorhous, and expression of the Sre1 N-terminal domain (Sre1N) increased carotenoid production more than twofold compared to wild-type. Overall, our results indicate that in X. dendrorhous transcriptional regulation of genes in the mevalonate pathway control production of the isoprenoid derivatives, carotenoids and sterol. Our results provide new insights into the conserved regulatory functions of SREBP/Sre1 and identify pointing to the SREBP pathway as a potential target to enhance carotenoid production in X. dendrorhous.

Csn5 Is Required for the Conidiogenesis and Pathogenesis of the Alternaria alternata Tangerine Pathotype

The COP9 signalosome (CSN) is a highly conserved protein complex involved in the ubiquitin-proteasome system. Its metalloisopeptidase activity resides in subunit 5 (CSN5). Functions of csn5 in phytopathogenic fungi are poorly understood. Here, we knocked out the csn5 ortholog (Aacsn5) in the tangerine pathotype of Alternaria alternata. The ΔAacsn5 mutant showed a moderately reduced growth rate compared to the wildtype strain and was unable to produce conidia. The growth of ΔAacsn5 mutant was not affected in response to oxidative and osmotic stresses. Virulence assays revealed that ΔAacsn5 induced no or significantly reduced necrotic lesions on detached citrus leaves. The defects in hyphal growth, conidial sporulation, and pathogenicity of ΔAacsn5 were restored by genetic complementation of the mutant with wildtype Aacsn5. To explore the molecular mechanisms of conidiation and pathogenesis underlying Aacsn5 regulation, we systematically examined the transcriptomes of both ΔAacsn5 and the wildtype. Generally, 881 genes were overexpressed and 777 were underexpressed in the ΔAacsn5 mutant during conidiation while 694 overexpressed and 993 underexpressed during infection. During asexual development, genes related to the transport processes and nitrogen metabolism were significantly downregulated; the expression of csn1-4 and csn7 in ΔAacsn5 was significantly elevated; secondary metabolism gene clusters were broadly affected; especially, the transcript level of the whole of cluster 28 and 30 was strongly induced. During infection, the expression of the host-specific ACT toxin gene cluster which controls the biosynthesis of the citrus specific toxin was significantly repressed; many other SM clusters with unknown products were also regulated; 86 out of 373 carbohydrate-active enzymes responsible for breaking down the plant dead tissues showed uniquely decreased expression. Taken together, our results expand our understanding of the roles of csn5 on conidiation and pathogenicity in plant pathogenic fungi and provide a foundation for future investigations.