Data from: Light sensing by opsins and fungal ecology: NOP-1 modulates entry into sexual reproduction in response to environmental cues

Understanding the genetic basis of the switch from asexual to sexual
lifestyles in response to sometimes rapid environmental changes is one of
the major challenges in fungal ecology. Light appears to play a critical
role in the asexual–sexual switch—but fungal genomes harbour diverse light
sensors. Fungal opsins are homologous to bacterial green-light-sensory
rhodopsins, and their organismal functions in fungi have not been well
understood. Three of these opsin-like proteins were widely distributed
across fungal genomes, but homologs of the Fusarium opsin-like protein
CarO were present only in plant-associated fungi. Key amino acids,
including potential retinal binding sites, functionally diverged on the
phylogeny of opsins. This diversification of opsin-like proteins could be
correlated with life history-associated differences among fungi in their
expression and function during morphological development. In Neurospora
crassa and related species, knockout of the opsin NOP-1 led to a phenotype
in the regulation of the asexual–sexual switch, modulating response to
both light and oxygen conditions. Sexual development commenced early in
∆nop-1 strains cultured in unsealed plates under constant blue and white
light. Furthermore, comparative transcriptomics showed that the expression
of nop-1 is light-dependent and that the ∆nop-1 strain abundantly
expresses genes involved in oxidative stress response, genes enriched in
NAD/NADP binding sites, genes with functions in proton transmembrane
movement and catalase activity, and genes involved in the homeostasis of
protons. Based on these observations, we contend that light and oxidative
stress regulate the switch via light-responsive and ROS pathways in model
fungus N. crassa and other fungi.

解析真菌响应偶发快速环境变化时，从无性生殖到有性生殖生活方式转变的遗传基础，是真菌生态学领域的核心挑战之一。光照被认为在无性-有性生殖转变中发挥关键调控作用，但真菌基因组中蕴含着多样的光感受器。真菌视蛋白（opsins）与细菌绿光感受视紫红质同源，但其在真菌体内的整体生物学功能尚未得到充分阐释。其中三类类视蛋白在真菌基因组中广泛分布，但镰孢菌（Fusarium）类视蛋白CarO的同源蛋白仅存在于植物关联真菌中。包括潜在视黄醛结合位点在内的关键氨基酸位点，在视蛋白的系统发育进程中发生了功能分化。类视蛋白的这种功能分化，可能与不同真菌在形态发育过程中表达模式与生物学功能的生活史相关差异存在关联。在粗糙脉孢霉（Neurospora crassa）及其近缘物种中，敲除视蛋白NOP-1会导致无性-有性生殖调控表型异常，进而调控其对光照与氧气条件的响应。在持续蓝光与白光照射的未封口培养板中，Δnop-1突变菌株的有性生殖发育进程会提前启动。此外，比较转录组学分析结果显示，nop-1的表达具有光照依赖性；且Δnop-1菌株会大量表达参与氧化应激响应的基因、富集NAD/NADP结合位点的基因、具备质子跨膜转运与过氧化氢酶活性功能的基因，以及参与质子稳态维持的基因。基于上述观测结果，我们认为在模式真菌粗糙脉孢霉（N. crassa）及其他真菌中，光照与氧化应激可通过光响应通路与活性氧（Reactive Oxygen Species, ROS）信号通路调控无性-有性生殖的转变。