Cork cambium (or phellogen) is a secondary meristem responsible for the formation of phelloderm and phellem/cork, which together compose the periderm. In Quercus suber L., the phellogen is active throughout the entire life of the tree, producing a continuous and renewable outer bark of cork. To identify specific candidate genes associated with cork cambium activity and phellem differentiation, we performed a comparative transcriptomic study of Q. suber secondary growth tissues (xylem and phellogen/phellem) using RNA-seq. The present work provides a high-resolution map of all the transcripts identified in the phellogen/phellem tissues. A total of 6013 differentially expressed genes were identified, with 2875 of the transcripts being specifically enriched during the cork formation process versus secondary xylem formation. Furthermore, cork samples originating from the original phellogen (`virgin’ cork) and from a traumatic phellogen (`amadia’ cork) were also compared. Our results point to a shortlist of potentially relevant candidate genes regulating phellogen activity and phellem differentiation, including novel genes involved in the suberization process, as well as genes associated to ethylene and jasmonate signaling and to meristem function. The future functional characterization of some of the identified candidate genes will help to elucidate the molecular mechanisms underlying cork cambium activity and phellem differentiation.

中文翻译：

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Phellem与木质部：全基因组转录组分析揭示了软木栎中软木形成的新型调节剂

黄柏形成层（或黄柏）是次生分生组织，负责形成黄皮和黄柏/软木塞，它们共同构成皮层。在Quercus suber L.中，黄原素在树的整个生命周期中都是活跃的，产生连续且可再生的软木外皮。为了识别与木栓形成层活动和木栓层分化相关的具体候选基因，我们进行的比较研究转录Q.苏伯二次生长组织（木质部和黄原/胶体）使用RNA-seq。本工作提供了在发色原/生胶组织中鉴定的所有转录本的高分辨率图。共鉴定了6013个差异表达的基因，其中2875个转录物在软木塞形成过程中相对于次生木质部形成过程中得到了特异性富集。此外，还比较了源自原始黄原胶（“原始”软木塞）和创伤性黄原胶（“ amadia”软木塞）的软木样品。我们的结果指出了可能的相关候选基因的短名单，这些候选基因可调控植物纤维蛋白原的活性和生胶酶的分化，包括参与干化过程的新基因，以及与乙烯和茉莉酮酸酯信号传导以及分生组织功能相关的基因。