Department of Plant Pathology and Microbiology, Robert H. Smith Faculty of Agriculture Food and Environment, Hebrew University of Jerusalem, Rehovot, Israel.
Department of Microbiology and Molecular Genetics, The Institute for Medical Research Israel-Canada, Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel.
mBio. 2019 Dec 3;10(6):e02623-19. doi: 10.1128/mBio.02623-19.
The ability to withstand UV damage shapes the ecology of microbes. While mechanisms of UV tolerance were extensively investigated in microorganisms regularly exposed to the sun, far less is known about UV repair of soilborne microorganisms. is a soilborne fungal plant pathogen that is resistant to UV light. We hypothesized that its UV repair capacity is induced to deal with irregular sun exposure. Unlike the SOS paradigm, our analysis revealed only sporadic increases and even decreases in UV repair gene expression following UVC irradiation or exposure to visible light. Strikingly, a major factor determining the expression of UV repair genes was the developmental status of the fungus. At the early stages of germination, the expression of photolyase increased while the expression of UV endonuclease decreased, and then the trend was reversed. These gene expression oscillations were dependent on cell cycle progression. Consequently, the contribution of photoreactivation to UV repair and survival was stronger at the beginning of germination than later when a filament was established. germinates following cues from the host. Early on in germination, it is most vulnerable to UV; when the filament is established, the pathogen is protected from the sun because it is already within the host tissue. infects plants through the roots and therefore is not exposed to the sun regularly. However, the ability to survive sun exposure expands the distribution of the population. UV from the sun is toxic and mutagenic, and to survive sun exposure, fungi encode several DNA repair mechanisms. We found that has a gene expression program that activates photolyase at the first hours of germination when the pathogen is not established in the plant tissue. Later on, the expression of photolyase decreases, and the expression of a light-independent UV repair mechanism increases. We suggest a novel point of view to a very fundamental question of how soilborne microorganisms defend themselves against sudden UV exposure.
耐受紫外线损伤的能力塑造了微生物的生态。虽然经常暴露在阳光下的微生物的紫外线耐受机制已被广泛研究，但对土壤微生物的紫外线修复知之甚少。 是一种土壤真菌植物病原体，对紫外线有抵抗力。我们假设它的紫外线修复能力是为了应对不规则的阳光暴露而被诱导产生的。与 SOS 模式不同，我们的分析表明，在 UVC 照射或可见光暴露后，紫外线修复基因的表达仅偶尔增加，甚至减少。引人注目的是，决定紫外线修复基因表达的一个主要因素是真菌的发育状态。在萌发的早期阶段，光解酶的表达增加，而紫外线内切酶的表达减少，然后趋势发生逆转。这些基因表达的振荡依赖于细胞周期的进展。因此，光复活对紫外线修复和存活的贡献在萌发开始时比后来建立丝状时更强，当时已经建立了丝状。 根据宿主的信号发芽。在萌发的早期，它对紫外线最敏感；当建立丝状时，由于病原体已经在宿主组织内，它可以免受阳光的伤害。 通过根部感染植物，因此不会经常暴露在阳光下。然而，耐受阳光暴露的能力扩大了种群的分布范围。来自太阳的紫外线具有毒性和致突变性，为了在阳光暴露下生存，真菌编码了几种 DNA 修复机制。我们发现， 在病原体尚未在植物组织中建立时，它有一种基因表达程序，在萌发的最初几个小时激活光解酶。后来，光解酶的表达减少，而一种不依赖光的紫外线修复机制的表达增加。我们提出了一个新的观点，即探讨土壤微生物如何防御突然的紫外线暴露这一非常基本的问题。
