The effect of Aspergillus luchuensis pectin methylesterase genes pmeA and pmeB on methanol production in sweet potato shochu.

To reduce the methanol content in sweet potato shochu, we studied the pectin methylesterase genes of the shochu-koji mold Aspergillus luchuensis. We found the following three homologs of pectin methyleseterase in the genome of A. luchuensis: pmeA, pmeB, and pmeC. Using pectin as a substrate, the methanol-producing activity of the recombinant of each gene expressed in A. luchuensis was examined and found to be present in recombinant PmeA and PmeB. Additionally, small-scale fermentation of sweet potato shochu using disruptions of pmeA and pmeA-pmeB in A. luchuensis (∆pmeA and ∆pmeApmeB) resulted in significant reduction of the methanol content. Taken together, we revealed that the A. luchuensis pmeA gene was mainly involved in methanol production in sweet potato shochu.

Identification of Genes Involved in the Synthesis of the Fungal Cell Wall Component Nigeran and Regulation of Its Polymerization in Aspergillus luchuensis.

Certain Aspergillus and Penicillium spp. produce the fungal cell wall component nigeran, an unbranched d-glucan with alternating α-1,3- and α-1,4-glucoside linkages, under nitrogen starvation. The mechanism underlying nigeran biosynthesis and the physiological role of nigeran in fungal survival are not clear. We used RNA sequencing (RNA-seq) to identify genes involved in nigeran synthesis in the filamentous fungus Aspergillus luchuensis when grown under nitrogen-free conditions. agsB, which encodes a putative α-1,3-glucan synthase, and two adjacent genes (agtC and gnsA) were upregulated under conditions of nitrogen starvation. Disruption of agsB in A. luchuensis (ΔagsB) resulted in the complete loss of nigeran synthesis. Furthermore, the overexpression of agsB in an Aspergillus oryzae strain that cannot produce nigeran resulted in nigeran synthesis. These results indicated that agsB encodes a nigeran synthase. Therefore, we have renamed the A. luchuensis agsB gene the nigeran synthase gene (nisA). Nigeran synthesis in an agtC mutant (ΔagtC) increased to 121%; conversely, those in the ΔgnsA and ΔagtC ΔgnsA strains decreased to 64% and 63%, respectively, compared to that in the wild-type strain. Our results revealed that AgtC and GnsA play an important role in regulating not only the quantity of nigeran but also its polymerization. Collectively, our results demonstrated that nisA (agsB) is essential for nigeran synthesis in A. luchuensis, whereas agtC and gnsA contribute to the regulation of nigeran synthesis and its polymerization. This research provides insights into fungal cell wall biosynthesis, specifically the molecular evolution of fungal α-glucan synthase genes and the potential utilization of nigeran as a novel biopolymer. IMPORTANCE The fungal cell wall is composed mainly of polysaccharides. Under nitrogen-free conditions, some Aspergillus and Penicillium spp. produce significant levels of nigeran, a fungal cell wall polysaccharide composed of alternating α-1,3/1,4-glucosidic linkages. The mechanisms regulating the biosynthesis and function of nigeran are unknown. Here, we performed RNA sequencing of Aspergillus luchuensis cultured under nitrogen-free or low-nitrogen conditions. A putative α-1,3-glucan synthase gene, whose transcriptional level was upregulated under nitrogen-free conditions, was demonstrated to encode nigeran synthase. Furthermore, two genes encoding an α-glucanotransferase and a hypothetical protein were shown to be involved in controlling the nigeran content and molecular weight. This study reveals genes involved in the synthesis of nigeran, a potential biopolymer, and provides a deeper understanding of fungal cell wall biosynthesis.

Expression profiles of amylolytic genes in AmyR and CreA transcription factor deletion mutants of the black koji mold Aspergillus luchuensis.

The black koji mold, Aspergillus luchuensis, which belongs to Aspergillus section Nigri, is used for the production of traditional Japanese spirits (shochu) mainly in the southern districts of Japan. This mold is known to produce amylolytic enzymes essential for shochu production; however, mechanisms regulating amylolytic gene expression in A. luchuensis have not been studied in as much detail as those in the yellow koji mold, Aspergillus oryzae. Here, we examined the gene expression profiles of deletion mutants of transcription factors orthologous to A. oryzae AmyR and CreA in A. luchuensis. A. luchuensis produces acid-unstable (AmyA) and acid-stable (AsaA) α-amylases. AmyA production and amyA gene expression were not influenced by amyR or creA deletion, indicating that amyA was constitutively expressed. In contrast, asaA gene expression was significantly down- and upregulated upon deletion of amyR and creA, respectively. Furthermore, the glaA and agdA genes (encoding glucoamylase and α-glucosidase, respectively) showed expression profiles similar to those of asaA. Thus, genes that play pivotal roles in starch saccharification, asaA, glaA, and agdA, were found to be regulated by AmyR and CreA. Moreover, despite previous reports on AsaA being only produced in solid-state culture, deletion of the ortholog of A. oryzae flbC, which is involved in the expression of the solid-state culture-specific genes, did not affect AsaA α-amylase activity, suggesting that FlbC was not associated with asaA expression.

Construction of transcription factor gene deletion library of Aspergillus luchuensis.

We selected 96 genes of Aspergillus luchuensis for the construction of a transcription factor gene deletion library. Of these, we successfully deleted 93 genes using Agrobacterium-mediated transformation (AMT) of A. luchuensis RIB 2604 ΔligD strains. We obtained only heterokaryonic strains after deletions of adaB, anBH1, hacA, hapB, hsf1, metR, and sonC gene, and additionally, could not obtain deletion strains for genes abaA and mcmA. The deletion strains will be available through our website (https://www.nrib.go.jp).

Development of an itraconazole resistance gene as a dominant selectable marker for transformation in Aspergillus oryzae and Aspergillus luchuensis.

There are only a few combinations of antifungal drugs with known resistance marker genes in the Aspergillus species; therefore, the transformation of their wild-type strains is limited. In this study, to develop the novel dominant selectable marker for itraconazole, a fungal cell membrane synthesis inhibitor, we focused on Aspergillus luchuensis cyp51A (Alcyp51A), which encodes a 14-α-sterol demethylase related to the steroid synthesis pathway. We found that the G52R mutation in AlCyp51A and the replacement of the native promoter with a high-expression promoter contributed to itraconazole resistance in Aspergillus oryzae, designated as itraconazole resistant gene (itrA). The random integration in the A. luchuensis genome of the itrA marker cassette gene also allowed for transformation using itraconazole. Therefore, we succeed in developing a novel itraconazole resistance marker as a dominant selectable marker for transformation in A. oryzae and A. luchuensis.

Downregulation of the ypdA Gene Encoding an Intermediate of His-Asp Phosphorelay Signaling in Aspergillus nidulans Induces the Same Cellular Effects as the Phenylpyrrole Fungicide Fludioxonil.

Many eukaryotic histidine-to-aspartate (His-Asp) phosphorelay systems consist of three types of signal transducers: a His-kinase (HK), a response regulator (RR), and a histidine-containing phosphotransfer intermediate (HPt). In general, the HPt acts as an intermediate between the HK and the RR and is indispensable for inducing appropriate responses to environmental stresses. In a previous study, we attempted but were unable to obtain deletion mutants of the ypdA gene in order to characterize its function in the filamentous fungus Aspergillus nidulans. In the present study, we constructed the CypdA strain in which ypdA expression is conditionally regulated by the A. nidulans alcA promoter. We constructed CypdA strains with RR gene disruptions (CypdA-sskAΔ, CypdA-srrAΔ, and CypdA-sskAΔsrrAΔ). Suppression of YpdA induced by ypdA downregulation activated the downstream HogA mitogen-activated protein kinase cascade. YpdA suppression caused severe growth defects and abnormal hyphae, with features such as enhanced septation, a decrease in number of nuclei, nuclear fragmentation, and hypertrophy of vacuoles, both regulated in an SskA-dependent manner. Fludioxonil treatment caused the same cellular responses as ypdA suppression. The growth-inhibitory effects of fludioxonil and the lethality caused by ypdA downregulation may be caused by the same or similar mechanisms and to be dependent on both the SskA and SrrA pathways.

Phenolic acid decarboxylase of Aspergillus luchuensis plays a crucial role in 4-vinylguaiacol production during awamori brewing.

Aspergillus luchuensis has been used to produce awamori, a distilled liquor, in Okinawa, Japan. Vanillin, derived from ferulic acid (FA) in rice grains, is one of the characteristic flavors in aged and matured awamori, known as kusu. Decarboxylation of FA leads to the production of 4-vinylguaiacol (4-VG), which is converted to vanillin by natural oxidization. However, the mechanism underlying FA conversion to 4-VG has remained unknown in awamori brewing. In our previous studies, we showed that phenolic acid decarboxylase from A. luchuensis (AlPAD) could catalyze the conversion of FA to 4-VG, and that AlPAD is functionally expressed during koji making (Maeda et al., J. Biosci. Bioeng., 126, 162-168, 2018). In this study, to understand the contribution of AlPAD to 4-VG production in awamori brewing, we created an alpad disruptant (Δalpad) and compared its 4-VG productivity to that of the wild-type strain. The amount of 4-VG in the distillate of moromi prepared with the wild-type strain showed a significant increase, proportional to the time required for koji making. In the Δalpad strain, the amount of 4-VG was very small and remained unchanged during the koji making. In an awamori brewing test using koji harvested 42-66 h after inoculation, the contribution of AlPAD to 4-VG production was in the range of 88-94 %. These results indicate that AlPAD plays a key role in 4-VG production during awamori brewing.

Aspergillus luchuensis fatty acid oxygenase ppoC is necessary for 1-octen-3-ol biosynthesis in rice koji.

Awamori is a distilled spirit produced in Okinawa Prefecture, in southern Japan. Awamori contains the volatile organic compound 1-octen-3-ol, an important flavor component. Here, using solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GCMS), we demonstrate that the black koji mold Aspergillus luchuensis produces 1-octen-3-ol in rice koji. To examine the role of the fatty acid oxygenase genes ppoA and ppoC in 1-octen-3-ol biosynthesis by A. luchuensis, we constructed ppoA and ppoC disruptants, ΔppoA and ΔppoC, respectively, via protoplast-PEG transformation. No clear differences in growth and conidiation were observed between the transformants and the parent strain. Volatile compounds in rice koji prepared using these gene disruptants were analyzed by SPME-GCMS. The amount of 1-octen-3-ol contained in koji produced by the ΔppoA strain was the same as that produced by the parental strain. In contrast, although the ΔppoC strain grew on the rice koji, 1-octen-3-ol was not detected. These results indicate that ppoC is involved in 1-octen-3-ol biosynthesis in A. luchuensis.

Effect of pepA deletion and overexpression in Aspergillus luchuensis on sweet potato shochu brewing.

The mash of sweet potato shochu (Japanese distilled spirit) has a low pH value because the shochu koji mold produces a large amount of citric acid, which prevents germ contamination. In this study, we examined acid protease PepA's role in shochu production. For this purpose, we constructed pepA deletion and overexpression strains, using a black koji mold Aspergillus luchuensis RIB 2604 (NBRC 4314), with the Agrobacterium-mediated transformation method. The rice koji, prepared using a pepA disruptant (ΔpepA) and pepA-overexpressing strain (OEpepA), demonstrated 1/2- and 24-fold acid protease activities compared to that prepared using the parental strain, respectively. A small-scale test of sweet potato shochu brewing indicated the mash of ΔpepA had a lower amino acid concentration, while the mash of OEpepA had a higher concentration than that produced by the parental strain. Therefore, the mash amino acid concentrations were proportional to these strains' acid proteases activities. After distilling these mashes, we examined each shochu's aroma components. Shochu prepared using ΔpepA had relatively higher aroma components, such as alcohol and ester, compared to that prepared using parental strains. Meanwhile, shochu prepared using OEpepA had lower aroma components than that prepared using the parental strains. Based on these results, the amount of shochu aroma components showed an inverse correlation to the acid protease activity in the mash. Thus, the koji mold's acid protease content had a greater influence on the aroma qualities of sweet potato shochu. Accordingly, we have discussed the possibility of the breeding of shochu koji mold with acid protease as an indicator.

Influence of α-1,3-glucan synthase gene agsE on protoplast formation for transformation of Aspergillus luchuensis.

Aspergillus luchuensis NBRC4314 recently underwent genome sequencing. We have not used the frequently used protoplast-polyethylene glycol (PEG) method but have used agrobacterium-mediated transformation (AMT) to genetically engineer this strain because it was difficult to generate protoplasts using commercial cell wall lytic enzymes. In this study, we initially investigated the various conditions for protoplast formation in A. luchuensis. We found that A. luchuensis protoplasts could be generated using a minimal medium for the preculture medium, a static culture for the preculture condition, and Yatalase and α-1,3-glucanase as cell-wall lytic enzymes. These protoplasts could then be transformed with the protoplast-PEG method. Because α-1,3-glucanase was needed to form protoplasts in A. luchuensis, we investigated the role of the α-1,3-glucan synthase gene agsE in protoplast formation, one of five α-1,3-glucan synthase genes in A. luchuensis and a homolog of the major α-1,3-glucan synthase agsB in Aspergillus nidulans. We disrupted agsE in A. luchuensis (ΔagsE) with AMT and found that protoplast formation in ΔagsE was comparable with protoplast formation in Aspergillus oryzae with Yatalase. The ΔagsE protoplasts were also competent for transformation with the protoplast-PEG method. Hence, agsE appears to inhibit protoplast formation in A. luchuensis.

An updated data portal for fungal allergens with curated information.

Allergens originating from fungal components abundantly exist in and around human life. We constructed a data portal specific for fungal allergens that includes genomic data from four Aspergillus species used by beverage industries. The fungal database contains the information of nucleotide sequences, which are similar to the coding region of already known allergens in the public database. The database will accelerate allergen identification and prediction in the fungal research field.

Cellular responses to the expression of unstable secretory proteins in the filamentous fungus Aspergillus oryzae.

Filamentous fungi are often used as cell factories for recombinant protein production because of their ability to secrete large quantities of hydrolytic enzymes. However, even using strong transcriptional promoters, yields of nonfungal proteins are generally much lower than those of fungal proteins. Recent analyses revealed that expression of certain nonfungal secretory proteins induced the unfolded protein response (UPR), suggesting that they are recognized as proteins with folding defects in filamentous fungi. More recently, however, even highly expressed endogenous secretory proteins were found to evoke the UPR. These findings raise the question of whether the unfolded or misfolded state of proteins is selectively recognized by quality control mechanisms in filamentous fungi. In this study, a fungal secretory protein (1,2-α-D-mannosidase; MsdS) with a mutation that decreases its thermostability was expressed at different levels in Aspergillus oryzae. We found that, at moderate expression levels, wild-type MsdS was secreted to the medium, while the mutant was not. In the strain with a deletion for the hrdA gene, which is involved in the endoplasmic reticulum-associated degradation pathway, mutant MsdS had specifically increased levels in the intracellular fraction but was not secreted. When overexpressed, the mutant protein was secreted to the medium to a similar extent as the wild-type protein; however, the mutant underwent hyperglycosylation and induced the UPR. Deletion of α-amylase (the most abundant secretory protein in A. oryzae) alleviated the UPR induction by mutant MsdS overexpression. These findings suggest that misfolded MsdS and unfolded species of α-amylase might act synergistically for UPR induction.

Self-excising Cre/mutant lox marker recycling system for multiple gene integrations and consecutive gene deletions in Aspergillus oryzae.

In this study, we developed a self-excising Cre/loxP-mediated marker recycling system with mutated lox sequences to introduce a number of biosynthetic genes into Aspergillus oryzae. To construct the self-excising marker cassette, both the selectable marker, the Aspergillus nidulans adeA gene, and the Cre recombinase gene (cre), conditionally expressed by the xylanase-encoding gene promoter, were designed to be located between the mutant lox sequences, lox66 and lox71. However, construction of the plasmid failed, possibly owing to a slight expression of cre downstream of the fungal gene promoter in Escherichia coli. Hence, to avoid the excision of the cassette in E. coli, a 71-bp intron of the A. oryzae xynG2 gene was inserted into the cre gene. The A. oryzae adeA deletion mutant was transformed with the resulting plasmid in the presence of glucose, and the transformants were cultured in medium containing xylose as the sole carbon source. PCR analysis of genomic DNA from resultant colonies revealed the excision of both the marker and Cre expression construct, indicating that the self-excising marker cassette was efficient at removing the selectable marker. Using the marker recycling system, hyperproduction of kojic acid could be achieved in A. oryzae by the introduction of two genes that encode oxidoreductase and transporter. Furthermore, we also constructed an alternative marker recycling cassette bearing the A. nidulans pyrithiamine resistant gene (ptrA) as a dominant selectable marker.

Detailed analysis of targeted gene mutations caused by the Platinum-Fungal TALENs in Aspergillus oryzae RIB40 strain and a ligD disruptant.

Transcription activator-like effector nucleases (TALENs), which can generate DNA double-strand breaks at specific sites in the desired genome locus, have been used in many organisms as a tool for genome editing. In Aspergilli, including Aspergillus oryzae, however, the use of TALENs has not been validated. In this study, we performed genome editing of A. oryzae wild-type strain via error of nonhomologous end-joining (NHEJ) repair by transient expression of high-efficiency Platinum-Fungal TALENs (PtFg TALENs). Targeted mutations were observed as various mutation patterns. In particular, approximately half of the PtFg TALEN-mediated deletion mutants had deletions larger than 1 kb in the TALEN-targeting region. We also conducted PtFg TALEN-based genome editing in A. oryzae ligD disruptant (ΔligD) lacking the ligD gene involved in the final step of the NHEJ repair and found that mutations were still obtained as well as wild-type. In this case, the ratio of the large deletions reduced compared to PtFg TALEN-based genome editing in the wild-type. In conclusion, we demonstrate that PtFg TALENs are sufficiently functional to cause genome editing via error of NHEJ in A. oryzae. In addition, we reveal that genome editing using TALENs in A. oryzae tends to cause large deletions at the target region, which were partly suppressed by deletion of ligD.

Genome sequence of Aspergillus luchuensis NBRC 4314.

Awamori is a traditional distilled beverage made from steamed Thai-Indica rice in Okinawa, Japan. For brewing the liquor, two microbes, local kuro (black) koji mold Aspergillus luchuensis and awamori yeast Saccharomyces cerevisiae are involved. In contrast, that yeasts are used for ethanol fermentation throughout the world, a characteristic of Japanese fermentation industries is the use of Aspergillus molds as a source of enzymes for the maceration and saccharification of raw materials. Here we report the draft genome of a kuro (black) koji mold, A. luchuensis NBRC 4314 (RIB 2604). The total length of nonredundant sequences was nearly 34.7 Mb, comprising approximately 2,300 contigs with 16 telomere-like sequences. In total, 11,691 genes were predicted to encode proteins. Most of the housekeeping genes, such as transcription factors and N-and O-glycosylation system, were conserved with respect to Aspergillus niger and Aspergillus oryzae An alternative oxidase and acid-stable α-amylase regarding citric acid production and fermentation at a low pH as well as a unique glutamic peptidase were also found in the genome. Furthermore, key biosynthetic gene clusters of ochratoxin A and fumonisin B were absent when compared with A. niger genome, showing the safety of A. luchuensis for food and beverage production. This genome information will facilitate not only comparative genomics with industrial kuro-koji molds, but also molecular breeding of the molds in improvements of awamori fermentation.

Substantial decrease in cell wall α-1,3-glucan caused by disruption of the kexB gene encoding a subtilisin-like processing protease in Aspergillus oryzae.

Disruption of the kexB encoding a subtilisin-like processing protease in Aspergillus oryzae (ΔkexB) leads to substantial morphological defects when the cells are grown on Czapek-Dox agar plates. We previously found that the disruption of kexB causes a constitutive activation of the cell wall integrity pathway. To understand how the disruption of the kexB affects cell wall organization and components, we analyzed the cell wall of ΔkexB grown on the plates. The results revealed that both total N-acetylglucosamine content, which constitutes chitin, and chitin synthase activities were increased. Whereas total glucose content, which constitutes ß-1,3-glucan and α-1,3-glucan, was decreased; this decrease was attributed to a remarkable decrease in α-1,3-glucan. Additionally, the ß-1,3-glucan in the alkali-insoluble fraction of the ΔkexB showed a high degree of polymerization. These results suggested that the loss of α-1,3-glucan in the ΔkexB was compensated by increases in the chitin content and the average degree of ß-1,3-glucan polymerization.

Mitogen-activated protein kinases MpkA and MpkB independently affect micafungin sensitivity in Aspergillus nidulans.

The transcriptional regulation of the MAPK mpkA and cell wall-related genes in Aspergillus nidulans differs from that of their counterparts in Saccharomyces cerevisiae. The A. nidulans MAPK MpkB is putatively orthologous to the yeast MAPKs Kss1p and Fus3p. To investigate MpkB and its contribution to cell wall integrity in A. nidulans, we constructed mpkB-disruptant (mpkB∆) strains. We previously showed that mpkA∆ strains exhibited reduced colony growth and increased sensitivity to the ß-1,3-glucan synthase inhibitor micafungin. Like mpkA∆ strains, mpkB∆ strains exhibited slight growth retardation and increased sensitivity to micafungin. Although MpkB-dependent signaling modulated the transcription of some cell wall-related genes, the sugar composition of cell wall fractions was similar among wild-type, mpkA∆, and mpkB∆ strains. To elucidate the relationship between MpkA and MpkB pathways, we compared conditional mutants of mpkB with those with mpkA deletion. Sensitivity testing suggested that MpkA and MpkB additively contribute to micafungin activity in A. nidulans.

Functional analysis of the α-1,3-glucan synthase genes agsA and agsB in Aspergillus nidulans: agsB is the major α-1,3-glucan synthase in this fungus.

Although α-1,3-glucan is one of the major cell wall polysaccharides in filamentous fungi, the physiological roles of α-1,3-glucan remain unclear. The model fungus Aspergillus nidulans possesses two α-1,3-glucan synthase (AGS) genes, agsA and agsB. For functional analysis of these genes, we constructed several mutant strains in A. nidulans: agsA disruption, agsB disruption, and double-disruption strains. We also constructed several CagsB strains in which agsB expression was controlled by the inducible alcA promoter, with or without the agsA-disrupting mutation. The agsA disruption strains did not show markedly different phenotypes from those of the wild-type strain. The agsB disruption strains formed dispersed hyphal cells under liquid culture conditions, regardless of the agsA genetic background. Dispersed hyphal cells were also observed in liquid culture of the CagsB strains when agsB expression was repressed, whereas these strains grew normally in plate culture even under the agsB-repressed conditions. Fractionation of the cell wall based on the alkali solubility of its components, quantification of sugars, and (13)C-NMR spectroscopic analysis revealed that α-1,3-glucan was the main component of the alkali-soluble fraction in the wild-type and agsA disruption strains, but almost no α-1,3-glucan was found in the alkali-soluble fraction derived from either the agsB disruption strain or the CagsB strain under the agsB-repressed conditions, regardless of the agsA genetic background. Taken together, our data demonstrate that the two AGS genes are dispensable in A. nidulans, but that AgsB is required for normal growth characteristics under liquid culture conditions and is the major AGS in this species.

Modified Cre-loxP recombination in Aspergillus oryzae by direct introduction of Cre recombinase for marker gene rescue.

Marker rescue is an important molecular technique that enables sequential gene deletions. The Cre-loxP recombination system has been used for marker gene rescue in various organisms, including aspergilli. However, this system requires many time-consuming steps, including construction of a Cre expression plasmid, introduction of the plasmid, and Cre expression in the transformant. To circumvent this laborious process, we investigated a method wherein Cre could be directly introduced into Aspergillus oryzae protoplasts on carrier DNA such as a fragment or plasmid. In this study, we define the carrier DNA (Cre carrier) as a carrier for the Cre enzyme. A mixture of commercial Cre and nucleic acids (e.g., pUG6 plasmid) was introduced into A. oryzae protoplasts using a modified protoplast-polyethylene glycol method, resulting in the deletion of a selectable marker gene flanked by loxP sites. By using this method, we readily constructed a marker gene-rescued strain lacking ligD to optimize homologous recombination. Furthermore, we succeeded in integrative recombination at a loxP site in A. oryzae. Thus, we developed a simple method to use the Cre-loxP recombination system in A. oryzae by direct introduction of Cre into protoplasts using DNA as a carrier for the enzyme.

Development of an efficient gene-targeting system in Aspergillus luchuensis by deletion of the non-homologous end joining system.

The industrial fungus Aspergillus luchuensis is used to produce a distilled spirit in Okinawa Island, Japan. Recently, the genome sequence of A. luchuensis RIB2604 (Aspergillus awamori NBRC 4314) was revealed and many functional genes are now expected to be analyzed. Gene targeting is necessary for analyzing the function of a gene; however, gene targeting frequencies in A. luchuensis are very low. To develop a highly efficient gene-targeting system for A. luchuensis, we disrupted A. luchuensis ligD (ALligD) encoding the human DNA ligase IV (ligIV) homologue using an Agrobacterium mediated gene transformation method. Deletion of ALligD dramatically improved homologous recombination efficiency (reached 100%) compared to that in the wild-type strain (0.8%), when 1000-bp homologous flanking regions were used. The ALligD disruptant showed no apparent defect in vegetative growth, and it exhibited increased sensitivity to phleomycin and high methyl methanesulphonate concentrations compared to the wild-type strain. Furthermore, using this ALligD disruptant, we disrupted ALpksP encoding an Aspergillus fumigatus polyketide synthase P (alb1/pksP) orthologue. The ALpksP disruptant displayed a decolourized conidial phenotype. This result indicated that ALpksP is a key factor for conidial black pigmentation in A. luchuensis. Our results indicate that the ALligD mutant is an efficient host for targeted gene disruption in A. luchuensis.