Abstract

Adventitious rooting of walnut species (Juglans L.) is known to be rather difficult, especially for mature trees. The adventitious root formation (ARF) capacities of mature trees can be significantly improved by rejuvenation. However, the underlying gene regulatory networks (GRNs) of rejuvenation remain largely unknown. To characterize such regulatory networks, we carried out the transcriptomic study using RNA samples of the cambia and peripheral tissues on the bottom of rejuvenated and mature walnut (Juglans hindsii × J. regia) cuttings during the ARF. The RNA sequencing data suggested that zeatin biosynthesis, energy metabolism and substance metabolism were activated by rejuvenation, whereas photosynthesis, fatty acid biosynthesis and the synthesis pathways for secondary metabolites were inhibited. The inter- and intra-module GRNs were constructed using differentially expressed genes. We identified 35 hub genes involved in five modules associated with ARF. Among these hub genes, particularly, beta-glucosidase-like (BGLs) family members involved in auxin metabolism were overexpressed at the early stage of the ARF. Furthermore, BGL12 from the cuttings of Juglans was overexpressed in Populus alba × P. glandulosa. Accelerated ARF and increased number of ARs were observed in the transgenic poplars. These results provide a high-resolution atlas of gene activity during ARF and help to uncover the regulatory modules associated with the ARF promoted by rejuvenation.

中文翻译：

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回春重塑转录网络以改善成熟胡桃树的根发生

摘要

众所周知，核桃树种 ( Juglans L.) 的不定生根相当困难，尤其是对于成熟的树木。成熟树的不定根形成 (ARF) 能力可以通过回春显着提高。然而，回春的潜在基因调控网络（GRNs）在很大程度上仍然未知。为了表征这种调节网络，我们使用再生和成熟核桃底部的 cambia 和外周组织的 RNA 样本进行了转录组学研究（Juglans hindsii × J. regia) ARF 期间的岩屑。RNA测序数据表明，玉米素生物合成、能量代谢和物质代谢被回春激活，而光合作用、脂肪酸生物合成和次级代谢产物的合成途径受到抑制。使用差异表达的基因构建模块间和模块内 GRN。我们确定了与 ARF 相关的五个模块中涉及的 35 个中枢基因。在这些枢纽基因中，特别是参与生长素代谢的β-葡萄糖苷酶样( BGLs ) 家族成员在 ARF 的早期过表达。此外，来自胡桃扦插的BGL12在白杨× P.腺体中过表达. 在转基因杨树中观察到 ARF 加速和 AR 数量增加。这些结果提供了 ARF 期间基因活动的高分辨率图谱，并有助于揭示与复兴促进的 ARF 相关的调节模块。