Data from: Gene expression differences between western redcedar seedlings resistant and susceptible to cedar leaf blight

Western redcedar (T. plicata) is an important Cupressaceae both at economic and cultural levels in the Pacific Northwest of North America. In adult trees, the species produces one of the most weathering-resistant heartwoods among conifers, making it one of the preferred species for outdoor applications. However, young T. plicata plants are susceptible to infection with cedar leaf blight (D. thujina), an important foliar pathogen that can be devastating in nurseries and small-spaced plantations. Despite that, variability in the resistance against D. thujina in T. plicata has been documented, and such a variability can be used to breed T. plicata for resistance against the pathogen. This investigation aimed to discern the phenotypic and gene expression differences between resistant and susceptible T. plicata seedlings to shed light on the potential constitutive resistance mechanisms against cedar leaf blight in western redcedar. The study consisted of two parts. First, the histological differences between four resistant and four susceptible families that were never infected with the pathogen were investigated. And second, the differences between one resistant and one susceptible family that were infected and not infected with the pathogen were analyzed at the chemical (C, N, mineral nutrients, lignin, fiber, starch, and terpenes) and gene expression (RNA-Seq) levels. The histological part showed that T. plicata seedlings resistant to D. thujina had constitutively thicker cuticles and lower stomata densities than susceptible plants. The chemical analyses revealed that, regardless of their infection status, resistant plants had higher foliar concentrations of sabinene and α-thujene, and higher levels of expression of transcripts that code for leucine-rich repeat receptor-like protein kinases and for bark storage proteins. In conclusion, the data collected in this study shows that constitutive differences at the phenotypic (histological and chemical) and gene expression level exist between T. plicata seedlings susceptible and resistant to D. thujina. Such differences have potential use for marker-assisted selection and breeding for resistance against cedar leaf blight in western redcedar in the future.北美太平洋西北沿岸地区，西方红雪松（Western redcedar，学名T. plicata）是兼具经济与文化价值的重要柏科（Cupressaceae）树种。成年植株所产出的心材为针叶树中耐候性最强的材种之一，使其成为户外应用的首选材种之一。然而，幼年T. plicata植株易受杉叶枯病（cedar leaf blight，病原菌为D. thujina）侵染——该病原菌为重要叶部病原菌，在苗圃与密植人工林中可造成毁灭性危害。尽管如此，学界已记录到T. plicata对D. thujina的抗性存在变异，该变异可用于培育抗该病原菌的T. plicata品种。本研究旨在明确抗、感杉叶枯病的T. plicata实生苗之间的表型与基因表达差异，以揭示西方红雪松抗杉叶枯病的潜在组成型抗性机制。本研究包含两部分内容：其一，对未接触过该病原菌的4个抗病家系与4个感病家系开展组织学差异分析；其二，分别对接种与未接种该病原菌的1个抗病家系与1个感病家系，从化学组分（碳、氮、矿质营养、木质素、纤维、淀粉与萜类物质）与基因表达（RNA测序（RNA-Seq））水平开展差异分析。组织学分析结果显示，抗D. thujina的T. plicata实生苗具有组成型更厚的角质层与较感病植株更低的气孔密度。化学组分分析表明，无论接种状态如何，抗病植株的叶片中桧烯（sabinene）与α-侧柏烯（α-thujene）的浓度均更高，且编码富含亮氨酸重复序列类受体蛋白激酶与树皮贮藏蛋白的转录本表达量也更高。综上，本研究采集的数据表明，抗、感D. thujina的T. plicata实生苗之间，在表型（组织学与化学组分）与基因表达水平均存在固有差异。此类差异未来可应用于西方红雪松抗杉叶枯病的标记辅助选择与抗性育种工作。