State Key Laboratory of Tree Genetics and Breeding, Key Laboratory of Genetics and Breeding in Forest Trees and Ornamental Plants, National Engineering Research Center of Tree Breeding and Ecological Restoration, Ministry of Education, The Tree and Ornamental Plant Breeding and Biotechnology Laboratory of National Forestry and Grassland Administration, College of Biological Sciences and Biotechnology, Beijing Forestry University, Beijing, 100083, China.
Plant J. 2024 Nov;120(3):1094-1111. doi: 10.1111/tpj.17039. Epub 2024 Sep 24.
Canker disease caused by the bacterium Lonsdalea populi is one of the most destructive diseases affecting poplar stems. However, the detailed stress response mechanisms of poplar have not been widely characterized. To explore the diverse regulatory RNA landscape and the function of key regulators in poplar subjected to L. populi stress, we integrated time-course experiment with mock-inoculation (CK) and inoculation (IN) with L. populi at the first, third, and sixth day (IN1, IN3, IN6) on Populus × euramericana cv. '74/76' (107), small RNA-seq, whole transcriptome-wide analysis, degradome analysis and transgenic experiments. A total of 98 differentially expressed (DE) miRNA, 17 974 DEmRNA, and 807 DElncRNA were identified in poplar infected by L. populi, presenting dynamic changes over the infection course. Regulatory networks among RNAs were further constructed. Notably, a network centered on ptc-miR482a in CK-vs-IN3 contained most DEGs. We show that miR482a and miR1448 are located in one transcript as a polycistron. Overexpression of pre-miR482a-miR1448 (OX482-1448) and pre-miR482a (OX482) increased poplar susceptibility to canker pathogen with reduced accumulation of reactive oxygen species, while the suppression of miR482a (STTM482) conferred poplar disease resistance. PHA7 was validated as the target of miR482a with degradome sequencing and tobacco transient co-transformation, its expression being downregulated in OX482-1448 and OX482 lines. Additionally, a series of phasiRNAs were triggered by miR482a targeting PHA7, forming regulatory cascades with more RLP, NBS-LRR, and PK genes, further verifying the defense function of miR482a. These findings provide insights for understanding the roles of ncRNAs and regulatory networks involved in poplar immunity.
柳树溃疡病菌引起的溃疡病是危害杨树茎干的最具破坏性的病害之一。然而，杨树的详细应激响应机制尚未得到广泛描述。为了探讨杨树在受到 L. populi 胁迫时多样化的调控 RNA 景观和关键调控因子的功能，我们将时间序列实验与模拟接种（CK）和接种（IN）相结合，分别在接种后的第 1、3 和 6 天（IN1、IN3、IN6）对美洲黑杨 × 欧美杨杂种（107）进行研究，使用小 RNA-seq、全转录组分析、降解组分析和转基因实验。在被 L. populi 感染的杨树中，共鉴定出 98 个差异表达（DE）miRNA、17974 个 DEmRNA 和 807 个 DELncRNA，它们在感染过程中呈现动态变化。进一步构建了 RNA 之间的调控网络。值得注意的是，在 CK-vs-IN3 中以 ptc-miR482a 为中心的网络包含了大多数 DEGs。我们表明，miR482a 和 miR1448 位于一个多顺反子转录本中。过表达 pre-miR482a-miR1448（OX482-1448）和 pre-miR482a（OX482）增加了杨树对溃疡病病原体的易感性，同时减少了活性氧的积累，而 miR482a 的抑制（STTM482）赋予了杨树抗病性。通过降解组测序和烟草瞬时共转化验证了 PHA7 是 miR482a 的靶标，其表达在 OX482-1448 和 OX482 系中下调。此外，miR482a 靶向 PHA7 触发了一系列 phasiRNAs，与更多的 RLP、NBS-LRR 和 PK 基因形成调控级联，进一步验证了 miR482a 的防御功能。这些发现为理解 ncRNAs 及其在杨树免疫中参与的调控网络的作用提供了新的见解。
