TY - JOUR A1 - Catanzaro, Ilaria A1 - Gerrits, Ruben A1 - Feldmann, Ines A1 - Gorbushina, Anna A1 - Onofri, Silvano A1 - Schumacher, Julia T1 - Deletion of the polyketide synthase‐encoding gene pks1 prevents melanization in the extremophilic fungus Cryomyces antarcticus N2 - Cryomyces antarcticus, a melanized cryptoendolithic fungus endemic to Antarctica, can tolerate environmental conditions as severe as those in space. Particularly, its ability to withstand ionizing radiation has been attributed to the presence of thick and highly melanized cell walls, which—according to a previous investigation—may contain both 1,8‐dihydroxynaphthalene (DHN) and L‐3,4 dihydroxyphenylalanine (L‐DOPA) melanin. The genes putatively involved in the synthesis of DHN melanin were identified in the genome of C. antarcticus. Most important is capks1 encoding a non‐reducing polyketide synthase (PKS) and being the ortholog of the functionally characterized kppks1 from the rock‐inhabiting fungus Knufia petricola. The co‐expression of CaPKS1 or KpPKS1 with a 4′‐phosphopantetheinyl transferase in Saccharomyces cerevisiae resulted in the formation of a yellowish pigment, suggesting that CaPKS1 is the enzyme providing the precursor for DHN melanin. To dissect the composition and function of the melanin layer in the outer cell wall of C. antarcticus, non‐melanized mutants were generated by CRISPR/Cas9‐mediated genome editing. Notwithstanding its slow growth (up to months), three independent non‐melanized Δcapks1 mutants were obtained. The mutants exhibited growth similar to the wild type and a light pinkish pigmentation, which is presumably due to carotenoids. Interestingly, visible light had an adverse effect on growth of both melanized wild‐type and non‐melanized Δcapks1 strains. Further evidence that light can pass the melanized cell walls derives from a mutant expressing a H2B‐GFP fusion protein, which can be detected by fluorescence microscopy. In conclusion, the study reports on the first genetic manipulation of C. antarcticus, resulting in non‐melanized mutants and demonstrating that the melanin is rather of the DHN type. These mutants will allow to elucidate the relevance of melanization for surviving extreme conditions found in the natural habitat as well as in space. KW - Astrobiology KW - Black fungi KW - CRISPR/Cas9 KW - DHN melanin KW - Cryptoendolithism PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-606599 DO - https://doi.org/10.1002/iub.2895 SN - 1521-6551 VL - 76 IS - 12 SP - 1072 EP - 1090 PB - Wiley AN - OPUS4-60659 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Catanzaro, Ilaria A1 - Gorbushina, Anna A1 - Onofri, Silvano A1 - Schumacher, Julia T1 - 1,8‐Dihydroxynaphthalene (DHN) melanin provides unequal protection to black fungi Knufia petricola and Cryomyces antarcticus from UV‐B radiation N2 - Black fungi on rock surfaces endure a spectrum of abiotic stresses, including UV radiation. Their ability to tolerate extreme conditions is attributed to the convergent evolution of adaptive traits, primarily highly melanized cell walls. However, studies on fungal melanins have not provided univocal results on their photoprotective functions. Here, we investigated whether the black fungi Knufia petricola and Cryomyces antarcticus only use DHN melanin or may employ alternative mechanisms to counteract UV‐induced damage. For this, melanized wild types and non‐melanized Δpks1 mutants were exposed to different doses of UV‐B (312 nm) followed by incubation in constant darkness or in light–dark cycles to allow light‐dependent DNA repair by photolyases (photoreactivation). C. antarcticus could tolerate higher UV‐B doses but was sensitive to white light, whereas K. petricola showed the opposite trend. DHN melanin provided UV‐B protection in C. antarcticus, whereas the same pigment or even carotenoids proved ineffective in K. petricola. Both fungi demonstrated functional photoreactivation in agreement with the presence of photolyase‐encoding genes. Our findings reveal that although the adaptive trait of DHN melanization commonly occurs across black fungi, it is not equally functional and that there are species‐specific adaptations towards either UV‐induced lesion avoidance or repair strategies. KW - Rock-inhabiting Ascomycetes KW - Pigment KW - Photoprotection KW - Photolyase KW - Disinfection PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-616859 DO - https://doi.org/10.1111/1758-2229.70043 VL - 16 IS - 6 SP - 1 EP - 13 PB - Wiley AN - OPUS4-61685 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -