Transcriptome-wide analysis of xylogenesis during growing season in Pinus canariensis. Pinus canariensis

Wood in conifers is mainly composed of tracheids. Some taxa, such as Pinus, present tracheids also in the rays, but are axial tracheids which constitute the vast majority of secondary xylem. Nevertheless, radial and axial parenchyma surrounding constitutive and traumatic resin ducts is known to serve as crucial reserve storage. These reserves are mobilized in response to traumatism, insect and pathogen attacks and defoliation, allowing the synthesis of resin, healing and, in few taxa, even resprouting. However, due to the low proportion of parenchymatic cells in secondary xylem relevant genes involved in their differentiation may have been missed in studies of transcriptomics of conifer wood formation. In this study we have used Pinus canariensis as a model species, given its comparatively high proportion of axial parenchyma. We have prepared two normalized libraries from its cambial zone, covering early- and late-wood differentiation. We have de novo assembled a transcriptome, and have analyzed the transcriptional profiles during the growing season, getting a more complete picture of wood formation in conifers. SUBMITTER_CITATION: Chano, V., López de Heredia, U., Collada, C., et al. (2017). Transcriptomic analysis of juvenile wood formation during the growing season in Pinus canariensis. Holzforschung, 0(0), pp. -. Retrieved 8 Aug. 2017, from doi:10.1515/hf-2017-0014 Overall design: mRNA samples were collected at 6 dates during the growing season in Pinus canariensis, supported by microscopical observation of cambial activity: March, April, May, June, July and September. Three biological replicates were collected for each time sampled, and therefore 18 mRNA samples were hybridazed in a one-color microarray experiment.

针叶树的木材主要由管胞（tracheids）构成。部分类群如松属（Pinus），其射线中也存在管胞，但轴向管胞是次生木质部（secondary xylem）的绝对主要组成部分。不过，围绕组成型与创伤诱导型树脂道的径向及轴向薄壁组织，作为关键的储备存储结构，其功能已得到明确证实。这些储备可响应创伤、昆虫与病原菌侵染以及落叶胁迫而被动员，用于树脂合成、伤口修复，在少数类群中甚至可辅助植株萌芽再生。然而，由于次生木质部中薄壁细胞占比极低，参与其分化的相关基因在针叶树木材形成的转录组研究中可能被遗漏。本研究选取轴向薄壁组织占比相对较高的加那利松（Pinus canariensis）作为模式物种，从其形成层区域（cambial zone）制备了两个标准化文库，分别覆盖早材与晚材的分化过程。我们通过从头组装获得了该物种的转录组（transcriptome），并分析了生长季内的转录谱，从而更全面地解析了针叶树的木材形成机制。提交引用：Chano, V., López de Heredia, U., Collada, C., et al. (2017). Transcriptomic analysis of juvenile wood formation during the growing season in Pinus canariensis. 《木材研究》（Holzforschung）, 0(0), pp. -. Retrieved 8 Aug. 2017, from doi:10.1515/hf-2017-0014。实验设计：本研究于加那利松生长季内的6个时间点采集mRNA样本，采样时间通过形成层活动的显微镜观测确定，分别为3月、4月、5月、6月、7月及9月。每个时间点设置3个生物学重复，总计18个mRNA样本用于单通道微阵列（microarray）杂交实验。