Liu Jun-Jun, Zamany Arezoo, Cartwright Charlie, Xiang Yu, Shamoun Simon F, Rancourt Benjamin
Natural Resources Canada, Canadian Forest Service, Victoria, BC, Canada.
British Columbia Ministry of Forests, Cowichan Lake Research Station, Mesachie Lake, BC, Canada.
Front Plant Sci. 2022 Jun 30;13:908680. doi: 10.3389/fpls.2022.908680. eCollection 2022.
Western hemlock () is highly susceptible to Annosus root and butt rot disease, caused by across its native range in western North America. Understanding molecular mechanisms of tree defense and dissecting genetic components underlying disease resistance will facilitate forest breeding and disease control management. The aim of this study was to profile host transcriptome reprogramming in response to pathogen infection using RNA-seq analysis. Inoculated seedlings were clearly grouped into three types: quantitative resistant (QR), susceptible (Sus), and un-infected (Uif), based on profiles of genes expressed in host tissues. Following assembly of a western hemlock reference transcriptome with more than 33,000 expressed genes, the defensive transcriptome reprogramming was characterized and a set of differentially expressed genes (DEGs) were identified with gene ontology (GO) annotation. The QR seedlings showed controlled and coordinated molecular defenses against biotic stressors with enhanced biosynthesis of terpenoids, cinnamic acids, and other secondary metabolites. The Sus seedlings showed defense responses to abiotic stimuli with a few biological processes enhanced (such as DNA replication and cell wall organization), while others were suppressed (such as killing of cells of other organism). Furthermore, non-synonymous single nucleotide polymorphisms (ns-SNPs) of the defense- and resistance-related genes were characterized with high genetic variability. Both phylogenetic analysis and principal coordinate analysis (PCoA) revealed distinct evolutionary distances among the samples. The QR and Sus seedlings were well separated and grouped into different phylogenetic clades. This study provides initial insight into molecular defense and genetic components of western hemlock resistance against the Annosus root and butt rot disease. Identification of a large number of genes and their DNA variations with annotated functions in plant resistance and defense promotes the development of genomics-based breeding strategies for improved western hemlock resistance to
北美西部铁杉（）对由引起的安诺苏根腐病和干基腐朽病高度敏感，这种病害在其北美西部的原生范围内广泛存在。了解树木防御的分子机制并剖析抗病性背后的遗传成分将有助于森林育种和病害控制管理。本研究的目的是通过RNA测序分析来描绘宿主转录组重编程对病原体感染的响应。根据宿主组织中表达的基因谱，接种的幼苗被明确分为三种类型：定量抗性（QR）、易感（Sus）和未感染（Uif）。在用超过33000个表达基因组装了北美西部铁杉参考转录组之后，对防御性转录组重编程进行了表征，并通过基因本体（GO）注释鉴定了一组差异表达基因（DEG）。QR幼苗表现出对生物胁迫的可控且协调的分子防御，萜类化合物、肉桂酸和其他次生代谢产物的生物合成增强。Sus幼苗表现出对非生物刺激的防御反应，一些生物学过程增强（如DNA复制和细胞壁组织），而其他过程则受到抑制（如杀死其他生物体的细胞）。此外，防御和抗性相关基因的非同义单核苷酸多态性（ns-SNP）具有高遗传变异性。系统发育分析和主坐标分析（PCoA）都揭示了样本之间不同的进化距离。QR和Sus幼苗被很好地分开并归入不同的系统发育分支。本研究为北美西部铁杉对安诺苏根腐病和干基腐朽病的分子防御和遗传成分提供了初步见解。鉴定大量具有注释功能的植物抗性和防御相关基因及其DNA变异，促进了基于基因组学的育种策略的发展，以提高北美西部铁杉对……的抗性
