摘要
乾旱脅迫嚴重限制作物產量和質量。snRNAs通過調控靶基因表達在植物生長，發育和脅迫響應方面發揮重要作用，但在蘋果中，對於它們乾旱脅迫耐受性的了解甚少。本研究中，我們通過高通量測序和降解組分析從蘋果中鑑定得到多個snRNAs和他們的靶基因。40個已知miRNAs和8個新的snRNAs在乾旱脅迫2或4小時時差異表達。我們實驗驗證5個挑選miRNA和它們靶基因的表達模式。我們發現一個miRNA，mdm-miR171i，特異性靶向並降解MsSCL26.1轉錄本。mdm-miR171i敲除和過量表達MsSCL26.1通過調節抗氧化酶基因的表達，特別是在抗壞血酸（AsA）代謝中發揮功能的MsMDHAR的表達來提高幹旱脅迫耐受性。瞬時表達分析表明MsSCL26.1通過正調控其啟動子P1區的活性來激活MsMDHAR轉錄。因此，miR171i-SCL26.1模塊通過調節抗氧化基因表達和AsA代謝來提高蘋果的乾旱脅迫耐受性。
Abstract
Drought stress severely restricts crop yield and quality. Small non-coding RNAs (snRNAs) play critical roles in plant growth, development, and stress responses by regulating target gene expression, but their roles in drought stress tolerance in apple (Malus domestica) are poorly understood. Here, we identified various snRNAs and their targets from the wild apple species Malus sieversii via high-throughput sequencing and degradome analysis. Forty known microRNAs (miRNAs) and eight new snRNAs were differentially expressed in response to 2 or 4 h of drought stress treatment. We experimentally verified the expression patterns of five selected miRNAs and their targets. We established that one miRNA, mdm-miR171i, specifically targeted and degraded SCARECROW-LIKE PROTEINS 26.1 (MsSCL26.1) transcripts. Both knockout of mdm-miR171i and overexpression of MsSCL26.1 improved drought stress tolerance in the cultivated apple line 'GL-3' (M. domestica Borkh.) by regulating the expression of antioxidant enzyme genes, especially that of MONODEHYDROASCORBATE REDUCTASE (MsMDHAR), which functions in ascorbic acid (AsA) metabolism under drought stress. Transient expression analysis demonstrated that MsSCL26.1 activates MsMDHAR transcription by positively regulating the activity of the P1 region in its promoter. Therefore, the miR171i-SCL26.1 module enhances drought stress tolerance in apple by regulating antioxidant gene expression and AsA metabolism.