Institute of Microbiology, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China.
College of Agricultural and Food Science, Zhejiang A&F University, Lin'an, Zhejiang, China.
Appl Environ Microbiol. 2019 Feb 6;85(4). doi: 10.1128/AEM.02459-18. Print 2019 Feb 15.
Fungal conidia serve as active ingredients of fungal insecticides but are sensitive to solar UV irradiation, which impairs double-stranded DNA (dsDNA) by inducing the production of cytotoxic cyclobutane pyrimidine dimers (CPDs) and (6-4)-pyrimidine-pyrimidine photoproducts (6-4PPs). This study aims to elucidate how CPD photolyase (Phr1) and 6-4PP photolyase (Phr2) repair DNA damage and photoreactivate UVB-inactivated cells in , a main source of fungal insecticides. Both Phr1 and Phr2 are proven to exclusively localize in the fungal nuclei. Despite little influence on growth, conidiation, and virulence, singular deletions of and resulted in respective reductions of 38% and 19% in conidial tolerance to UVB irradiation, a sunlight component most harmful to formulated conidia. CPDs and 6-4PPs accumulated significantly more in the cells of Δ and Δ mutants than in those of a wild-type strain under lethal UVB irradiation and were largely or completely repaired by Phr1 in the Δ mutant and Phr2 in the Δ mutant after optimal 5-h exposure to visible light. Consequently, UVB-inactivated conidia of the Δ and Δ mutants were much less efficiently photoreactivated than were the wild-type counterparts. In contrast, overexpression of either or in the wild-type strain resulted in marked increases in both conidial UVB resistance and photoreactivation efficiency. These findings indicate essential roles of Phr1 and Phr2 in photoprotection of from UVB damage and unveil exploitable values of both photolyase genes for improved UVB resistance and application strategy of fungal insecticides. Protecting fungal cells from damage from solar UVB irradiation is critical for development and application of fungal insecticides but is mechanistically not understood in , a classic insect pathogen. We unveil that two intranuclear photolyases, Phr1 and Phr2, play essential roles in repairing UVB-induced dsDNA lesions through respective decomposition of cytotoxic cyclobutane pyrimidine dimers and (6-4)-pyrimidine-pyrimidine photoproducts, hence reactivating UVB-inactivated cells effectively under visible light. Our findings shed light on the high potential of both photolyase genes for use in improving UVB resistance and application strategy of fungal insecticides.
真菌分生孢子作为真菌杀虫剂的有效成分，但对太阳紫外线照射敏感，紫外线照射会通过诱导产生细胞毒性环丁烷嘧啶二聚体（CPDs）和（6-4）-嘧啶-嘧啶光产物（6-4PPs）来破坏双链 DNA（dsDNA）。本研究旨在阐明真菌 中的 CPD 光解酶（Phr1）和 6-4PP 光解酶（Phr2）如何修复 DNA 损伤并光复活 UVB 失活的细胞， 是真菌杀虫剂的主要来源。已经证明 Phr1 和 Phr2 都专门定位于真菌核内。尽管对生长、分生孢子形成和毒力的影响很小，但 和 的单一缺失分别导致分生孢子对 UVB 照射的耐受性降低了 38%和 19%，而 UVB 是对配制成的分生孢子最有害的阳光成分。在致死性 UVB 照射下，Δ 和 Δ 突变体细胞中 CPDs 和 6-4PPs 的积累明显多于野生型菌株，并且在 Δ 突变体中 Phr1 和在 Δ 突变体中 Phr2 大量或完全修复。因此，与野生型相比，Δ 和 Δ 突变体的 UVB 失活分生孢子的光复活效率要低得多。相比之下，在野生型菌株中过表达 或 都会导致分生孢子对 UVB 的抵抗力和光复活效率显著提高。这些发现表明 Phr1 和 Phr2 在保护 免受 UVB 损伤方面发挥着重要作用，并揭示了这两种光解酶基因在提高 UVB 抗性和真菌杀虫剂应用策略方面的可利用价值。保护真菌细胞免受太阳 UVB 照射的损伤对于真菌杀虫剂的开发和应用至关重要，但在 ，一种经典的昆虫病原体中，其机制尚不清楚。我们揭示了两个核内光解酶，Phr1 和 Phr2，通过各自分解细胞毒性环丁烷嘧啶二聚体和（6-4）-嘧啶-嘧啶光产物，在可见光下有效修复 UVB 诱导的 dsDNA 损伤，从而在可见光下有效修复 UVB 失活的细胞。我们的发现揭示了这两种光解酶基因在提高真菌杀虫剂的 UVB 抗性和应用策略方面的巨大潜力。
