干旱胁迫下茶树（Camellia sinensis L.）响应miRNA 的鉴定及生理特性分析。

BACKGROUND: Drought stress is one of the major natural challenges in the main tea-producing regions of China. The tea plant (Camellia sinensis) is a traditional beverage plant whose growth status directly affects tea quality. Recent studies have revealed that microRNAs (miRNAs) play key functions in plant growth and development. Although some miRNAs have been identified in C. sinensis, little is known about their roles in the drought stress response of tea plants. RESULTS: Physiological characterization of Camellia sinensis 'Tieguanyin' under drought stress showed that the malondialdehyde concentration and electrical conductivity of leaves of drought-stressed plants increased when the chlorophyll concentration decreased under severe drought stress. We sequenced four small-RNA (sRNA) libraries constructed from leaves of plants subjected to four different treatments, normal water supply (CK); mild drought stress (T1); moderate drought stress (T2) and severe drought stress (T3). A total of 299 known mature miRNA sequences and 46 novel miRNAs were identified. Gene Ontology enrichment analysis revealed that most of the differentially expressed-miRNA target genes were related to regulation of transcription. Kyoto Encyclopedia of Genes and Genomes analysis revealed that the most highly enriched pathways under drought stress were D-alanine metabolism, sulfur metabolism, and mineral absorption pathways. Real-time quantitative PCR (qPCR) was used to validate the expression patterns of 21 miRNAs (2 up-regulated and 19 down-regulated under drought stress). The observed co-regulation of the miR166 family and their targets ATHB-14-like and ATHB-15-like indicate the presence of negative feedback regulation in miRNA pathways. CONCLUSIONS: Analyses of drought-responsive miRNAs in tea plants showed that most of differentially expressed-miRNA target genes were related to regulation of transcription. The results of study revealed that the expressions of phase-specific miRNAs vary with morphological, physiological, and biochemical changes. These findings will be useful for research on drought resistance and provide insights into the mechanisms of drought adaptation and resistance in C. sinensis.

背景：干旱胁迫是中国主要产茶区面临的主要自然挑战之一。茶树（Camellia sinensis）是一种传统的饮料植物，其生长状况直接影响茶叶品质。最近的研究表明，microRNAs（miRNAs）在植物生长发育中发挥着关键作用。虽然在茶树中已经鉴定出一些 miRNAs，但它们在茶树干旱胁迫响应中的作用知之甚少。

结果：对干旱胁迫下的茶树‘铁观音’进行生理特性分析表明，在严重干旱胁迫下，叶片叶绿素浓度下降的同时，丙二醛浓度和电导率增加。我们从正常供水（CK）、轻度干旱胁迫（T1）、中度干旱胁迫（T2）和重度干旱胁迫（T3）的茶树叶片中构建了四个小 RNA（sRNA）文库，共鉴定出 299 个已知成熟 miRNA 序列和 46 个新的 miRNA。基因本体论富集分析表明，差异表达-miRNA 靶基因大多与转录调控有关。京都基因与基因组百科全书分析表明，干旱胁迫下最富集的途径是 D-丙氨酸代谢、硫代谢和矿物质吸收途径。实时定量 PCR（qPCR）用于验证 21 个 miRNA（干旱胁迫下 2 个上调和 19 个下调）的表达模式。miR166 家族及其靶基因 ATHB-14-like 和 ATHB-15-like 的共调控表明 miRNA 途径存在负反馈调节。

结论：对茶树干旱响应 miRNAs 的分析表明，大多数差异表达-miRNA 靶基因与转录调控有关。研究结果表明，阶段性特异性 miRNAs 的表达随形态、生理和生化变化而变化。这些发现将有助于研究抗旱性，并为研究茶树的干旱适应和抗性机制提供思路。