Research Institute of Subtropical Forestry, Chinese Academy of Forestry, Hangzhou, 311400, China.
Research Institute of Subtropical Forestry, Chinese Academy of Forestry, Hangzhou, 311400, China.
Plant Physiol Biochem. 2021 Oct;167:163-173. doi: 10.1016/j.plaphy.2021.07.032. Epub 2021 Jul 28.
Orchids are distributed worldwide, and some species have considerable economic value. Orchid seeds are minute in size, simple in structure, and deficient in nutrient reserves. Asymbiotic seed germination is an important propagation strategy for orchids. MicroRNAs (miRNAs) play an essential role in seed germination. However, few studies have examined miRNAs involved in seed germination in orchids. Here, we conducted comparative small RNA sequencing at five stages to characterize the miRNAs involved in asymbiotic seed germination in Bletilla striata. A total of 253 known and 125 novel miRNAs were identified. Of them, 71 known and 29 novel miRNAs showed distinct expression among the five stages. Quantitative PCR revealed negative correlations of expression between differentially expressed miRNAs (DE miRNAs) and their targets. Function annotation and enrichment analyses of the targets of DE miRNAs between adjacent stages indicate that miRNA-target regulations are involved in many important processes during germination, such as signaling, biosynthesis, and transport of plant hormones. Twenty-two miRNAs were inferred to participate in plant hormone-related processes. The contents of abscisic acid, gibberellin A, indole-3-acetic acid, jasmonic acid, trans zeatin riboside, and N6-(Δ2-isopentenyl) adenine varied significantly among the five stages. Nine tested plant hormone-related miRNAs and their targets exhibited significant correlations with at least one plant hormone. 5'-RLM-RACE validated that a transcript encoding auxin response factor was cleaved by Bst-miR160e as predicted. For the first time, we characterized miRNAs associated with the asymbiotic seed germination of an orchid species, which will help understand the miRNA-mediated regulatory mechanism of seed germination in orchids.
兰花分布于世界各地，一些物种具有相当大的经济价值。兰花种子体积小、结构简单、营养储备不足。非共生种子萌发是兰花重要的繁殖策略。MicroRNAs (miRNAs) 在种子萌发中起着重要作用。然而，很少有研究探讨兰花种子萌发过程中涉及的 miRNAs。在这里，我们在五个阶段进行了比较小 RNA 测序，以研究不亲和种子萌发过程中 Bletilla striata 中涉及的 miRNAs。共鉴定出 253 个已知和 125 个新的 miRNAs。其中，71 个已知和 29 个新的 miRNAs 在五个阶段之间表现出明显的差异表达。定量 PCR 显示差异表达 miRNA (DE miRNAs) 与其靶标之间呈负相关。相邻阶段 DE miRNAs 靶标的功能注释和富集分析表明，miRNA-靶标调控参与了萌发过程中的许多重要过程，如信号转导、植物激素的生物合成和运输。22 个 miRNA 被推断参与了与植物激素相关的过程。五个阶段之间脱落酸、赤霉素 A、吲哚-3-乙酸、茉莉酸、反式玉米素核苷和 N6-（Δ2-异戊烯基）腺嘌呤的含量差异显著。测试的 9 个与植物激素相关的 miRNA 及其靶标与至少一种植物激素表现出显著相关性。5'-RLM-RACE 验证了预测的 auxin response factor 转录物被 Bst-miR160e 切割。这是首次对兰花非共生种子萌发相关的 miRNAs 进行了描述，这将有助于理解兰花种子萌发过程中 miRNA 介导的调控机制。
