Biology subjects

Maruyama, J.-i.

Publications and source records attributed to Maruyama, J.-i..

4 recordsLinked to original sources

bioRxiv2025

Biosynthesis of Kaitocephalin: A Neuroprotective Natural Product Featuring a Peptide-Like yet Non-Peptidic Scaffold

Kaitocephalin (KCP, 1) is a neuroprotective natural product that acts as an antagonist of ionotropic glutamate receptors, making it a highly promising lead for drug discovery. It possesses a unique scaffold composed of three amino acids connected via C-C bonds, which appears peptide-like but is formed without peptide bonds. In this study, we identified the KCP biosynthetic gene cluster (kpb cluster) in the producing fungus Eupenicillium shearii through integrated genomic and transcriptomic analyses. LC-MS/MS profiling and chemical derivatization of E. shearii extracts led to the discovery of four novel pathway-related metabolites (2-5). In vitro enzymatic assays with 2(S)-dechlorokaito lactate (4) as a substrate enabled functional characterization of KpbI, KpbM, and KpbB involved in KCP formation. Among them, the dioxygenase KpbI was found to catalyze an unprecedented two-step oxidation to form the D-serine moiety. In addition, isotope tracing experiments provided new insights into the origin of the L-proline moiety. These findings establish a foundation for future studies aimed at elucidating the complete biosynthetic mechanism of KCP. Table of Contents graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=50 SRC="FIGDIR/small/683206v1_ufig1.gif" ALT="Figure 1"> View larger version (12K): org.highwire.dtl.DTLVardef@189618aorg.highwire.dtl.DTLVardef@62d5deorg.highwire.dtl.DTLVardef@c71341org.highwire.dtl.DTLVardef@1c14e59_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2025

The increase in cell volume and nuclear number of the koji-fungus Aspergillus oryzae contributes to its high enzyme productivity

While the ratio of nuclei to cell volume is well regulated, it remains largely unexplored in multinucleate organisms. The koji-fungus Aspergillus oryzae, traditionally used in Japanese brewing and fermentation for over a thousand years, is now widely utilized in modern biotechnology as a host for enzyme production. We discovered that, over time in culture, hyphae become thicker, resulting in a tenfold increase in cell volume, and the number of nuclei in hyphal cells also increases tenfold, exceeding 200. The increase in cell volume and nuclear number is unique among the investigated Aspergillus species and correlates with its high enzyme production capabilities. Since nuclear number and cell volume are correlated, both must increase simultaneously for either to expand. Our analyses identified genetic factors and nutritional environmental signals involved in each of these increases. Increases in nuclear number and cell volume were also observed in other fungi bred for industrial use. This study not only deepens our understanding of the evolutionary processes that promote high enzyme productivity through fungal breeding, but also provides insights into the molecular mechanisms regulating cell volume and nuclear number in multinucleate organisms.

microbiology↗

bioRxiv2022

Multiple genes evolved for fungal septal pore plugging identified via large-scale localization and functional screenings

Multicellular organisms exhibit cytoplasmic exchange using porous structures for cooperation among cells. Fungal multicellular lineages have evolved septal pores for this function. Interconnected hyphal cells possess the risk of wound-related cytoplasmic loss unless the septal pores are plugged. However, the gene evolution of regulatory mechanisms underlying fungal septal pore plugging remains poorly understood. To identify novel septal components, 776 uncharacterized proteins were identified using genomic comparisons between septal pore-bearing and -lacking ascomycete species. We then determined their subcellular localizations, and in total 62 proteins localized to the septum or septal pore. We analyzed the effects of deleting the encoding genes on septal pore plugging upon hyphal wounding. Of the 62 proteins, 23 were involved in regulating septal pore plugging. Here, using orthologous group and phylogenetic analyses, this study suggests that septal pore regulation has evolved either by co-option of preexisting genes or by Pezizomycotina-specific gene acquisition.

microbiology↗

bioRxiv2021

Mitochondrial fission dysfunction alleviates heterokaryon incompatibility-triggered cell death in the industrial filamentous fungus Aspergillus oryzae

In filamentous fungi, cell-to-cell recognition is a fundamental requirement for the formation, development, and maintenance of complex hyphal networks. Basically, self/compatible individuals within the fungal species are capable of fusing together, a step important for crossbreeding, which results in the formation of viable vegetative heterokaryons. Conversely, the fusion of incompatible individuals does not result in the formation of viable hyphal networks, but it often leads to growth inhibition or cell death. Even though a number of studies have been conducted to investigate such incompatibility, the understanding of the associated molecular mechanism is still limited, and this restricts the possibility of crossbreeding incompatible individuals. Therefore, in this study, the characteristics of compatibility/incompatibility in the industrial filamentous fungus, Aspergillus oryzae, were comprehensively investigated. Protoplast fusion and co-culture assays indicated the existence of a correlation between strain phylogeny and compatibility/incompatibility features. Time-course fluorescence observations were employed to investigate the types of incompatible responses that are induced at different cellular levels upon incompatible cell fusion, which eventually lead to cell death. Propidium iodide-indicated cell death, ROS accumulation, and mitochondrial fragmentation were identified as the major responses, with mitochondrial fragmentation showing the most significant subcellular change immediately after incompatible cell fusion. Furthermore, the deletions of mitochondrial fission-related genes Aofis1 and Aodnm1 in incompatible pairing alleviated cell death, indicating that mitochondrial fission is an important mechanism by which incompatibility-triggered cell death occurs. Therefore, this study provides new insights about heterokaryon incompatibility. IMPORTANCEFor a long time, it was believed that as an asexual fungus, A. oryzae does not exhibit any sexual cycle. However, the fungus has two mating types, indicating the potential for sexual reproduction besides a known parasexual cycle. Therefore, given that viable heterokaryon formation following cell fusion is an important step required for genetic crossing, we explored the mechanism of incompatibility, which restricts the possibility of cell fusion in A. oryzae. Protoplast fusion and co-culture assays led to the identification of various vegetative compatible groups. Mitochondrial fragmentation was found to be the most significant incompatible cellular response that occurred in organelles during incompatible pairing, while the deletion of mitochondrial fission-related genes was identified as a strategy used to alleviate incompatibility-triggered cell death. Thus, this study revealed a novel mechanism by which mitochondrial fission regulates incompatible responses.

microbiology↗