Data Sheet 1_Local endoreduplication of the host is a conserved process during Phytomyxea–host interaction.docx

BackgroundEndoreduplication, a modified cell cycle, involves cells duplicating DNA without undergoing mitosis. This phenomenon is frequently observed in plants, algae, and animals. Biotrophic pathogens have been demonstrated to induce endoreduplication in plants to secure more space or nutrients.
MethodsIn this study, we investigated the endoreduplication process triggered by two phylogenetically distant Rhizaria organisms—Maullinia spp. (in brown algae) and Plasmodiophora brassicae (in plants)—by combining fluorescent in situ hybridization (FISH) with nuclear area measurements.
ResultsWe could confirm that Plasmodiophora brassicae (Plasmodiophorida) triggers endoreduplication in infected plants. For the first time, we also demonstrated pathogen-induced endoreduplication in brown algae infected with Maullinia ectocarpii and Maullinia braseltonii (Phagomyxida). We identified molecular signatures of endoreduplication in RNA-seq datasets of P. brassicae-infected Brassica oleracea and M. ectocarpii-infected Ectocarpus siliculosus.
DiscussionCell cycle switch proteins such as CCS52A1 and B in plants, CCS52 in algae, and the protein kinase WEE1 in plants were upregulated in RNA-seq datasets hinting at a potential role in the phytomyxean-induced transition from mitotic cell cycle to endocycle. By demonstrating the consistent induction of endoreduplication in hosts during phytomyxid infections, our study expands our understanding of Phytomyxea–host interaction. The induction of this cellular mechanism by phytomyxid parasites in phylogenetically distant hosts further emphasizes the importance of endoreduplication in these biotrophic interactions.

背景
内复制（endoreduplication）是一种修饰型细胞周期，指细胞在不经历有丝分裂的前提下完成DNA复制。该现象广泛分布于植物、藻类与动物类群中。已有研究表明，活体营养型病原体（biotrophic pathogens）可诱导植物发生内复制，以获取充足的生存空间与营养物质。
方法
本研究结合荧光原位杂交（FISH）与细胞核面积测量技术，针对两类系统发育距离较远的根变形虫门（Rhizaria）生物——褐藻寄生的Maullinia属（Maullinia spp.）以及植物寄生的芸苔根肿菌（Plasmodiophora brassicae）所触发的内复制过程展开研究。
结果
本研究证实，芸苔根肿菌（Plasmodiophorida）可诱导侵染宿主植物发生内复制。同时，本研究首次证明，被Maullinia ectocarpii与Maullinia braseltonii（Phagomyxida）侵染的褐藻中同样存在病原体诱导的内复制现象。我们在芸苔根肿菌侵染的甘蓝（Brassica oleracea）以及Maullinia ectocarpii侵染的水云（Ectocarpus siliculosus）的RNA测序（RNA-seq）数据集中，鉴定得到了内复制的分子特征。
讨论
细胞周期转换蛋白，如植物中的CCS52A1与CCS52B、藻类中的CCS52，以及植物中的蛋白激酶WEE1，在RNA-seq数据集中均呈现上调表达，提示这类蛋白可能在植黏菌纲（Phytomyxea）诱导的有丝分裂细胞周期向内复制周期的转换过程中发挥潜在功能。本研究证实植黏菌纲寄生菌侵染宿主时会一致性诱导内复制发生，拓展了学界对植黏菌-宿主互作机制的认知。植黏菌纲寄生菌可在系统发育距离较远的宿主中诱导该细胞机制，进一步凸显了内复制在这类活体营养型互作中的核心重要性。