Autophagy contributes to regulation of nuclear dynamics during vegetative growth and hyphal fusion in <i>Fusarium oxysporum</i>

In the fungal pathogen <i>Fusarium oxysporum</i>, vegetative hyphal fusion triggers nuclear mitotic division in the invading hypha followed by migration of a nucleus into the receptor hypha and degradation of the resident nucleus. Here we examined the role of autophagy in fusion-induced nuclear degradation. A search of the <i>F. oxysporum</i> genome database for autophagy pathway components identified putative orthologs of 16 core autophagy-related (<i>ATG</i>) genes in yeast, including the ubiquitin-like protein Atg8, which is required for the formation of autophagosomal membranes. <i>F. oxysporum Foatg8</i>Δ mutants were generated in a strain harboring H1-cherry fluorescent protein (ChFP)-labeled nuclei to facilitate analysis of nuclear dynamics. The <i>Foatg8</i>Δ mutants did not show MDC-positive staining in contrast to the wild type and the <i>FoATG8</i>-complemented (c<i>FoATG8</i>) strain, suggesting that FoAtg8 is required for autophagy in <i>F. oxysporum</i>. The <i>Foatg8</i>Δ strains displayed reduced rates of hyphal growth, conidiation, and fusion, and were significantly attenuated in virulence on tomato plants and in the nonvertebrate animal host <i>Galleria mellonella</i>. In contrast to wild-type hyphae, which are almost exclusively composed of uninucleated hyphal compartments, the hyphae of the <i>Foatg8</i>Δ mutants contained a significant fraction of hyphal compartments with 2 or more nuclei. The increase in the number of nuclei per hyphal compartment was particularly evident after hyphal fusion events. Time-lapse microscopy analyses revealed abnormal mitotic patterns during vegetative growth in the <i>Foatg8</i>Δ mutants. Our results suggest that autophagy mediates nuclear degradation after hyphal fusion and has a general function in the control of nuclear distribution in <i>F. oxysporum</i>.在真菌病原菌尖孢镰刀菌（*Fusarium oxysporum*）中，营养菌丝融合会触发侵入菌丝内的细胞核启动有丝分裂，随后一个细胞核迁移至受体菌丝，而受体菌丝内的驻留细胞核则被降解。本研究探讨了自噬（autophagy）在融合诱导的细胞核降解过程中发挥的作用。通过检索尖孢镰刀菌基因组数据库中的自噬通路组分，我们鉴定出16个酵母核心自噬相关（ATG）基因的推定同源物，其中包括泛素样蛋白Atg8——该蛋白是自噬体膜形成所必需的组分。我们在携带组蛋白H1-樱桃荧光蛋白（ChFP）标记细胞核的菌株背景中构建了*Foatg8*Δ缺失突变体，以方便对细胞核动态变化进行分析。与野生型菌株及*FoATG8*互补（c*FoATG8*）菌株不同，*Foatg8*Δ突变体未呈现MDC阳性染色，这表明FoAtg8是尖孢镰刀菌完成自噬过程所必需的蛋白。*Foatg8*Δ菌株表现出菌丝生长、产孢及菌丝融合速率下降的表型，且在番茄植株与非脊椎动物宿主大蜡螟（*Galleria mellonella*）中的致病力显著减弱。野生型菌丝几乎全部由单核菌丝室构成，而*Foatg8*Δ突变体的菌丝则含有显著比例的含2个或更多细胞核的菌丝室；这种每个菌丝室中细胞核数量增加的现象，在菌丝融合事件后尤为显著。延时显微镜分析结果显示，*Foatg8*Δ突变体在营养生长阶段存在异常的有丝分裂模式。本研究结果表明，自噬介导了菌丝融合后的细胞核降解过程，并在尖孢镰刀菌的细胞核分布调控中发挥了普遍功能。

搜集汇总

背景与挑战

背景概述

该数据集聚焦于尖孢镰刀菌（Fusarium oxysporum）中自噬在营养生长和菌丝融合过程中对核动力学的调控作用。通过生成Foatg8Δ突变体并结合显微镜分析，研究发现自噬缺失导致菌丝多核比例增加、生长减缓及毒力减弱，揭示了自噬在核降解和分布中的关键功能。数据集包含补充图、视频和文档，为相关生物学研究提供实验支持。