Boron Stress Responsive MicroRNAs and Their Targets in Barley

Boron stress is an environmental factor affecting plant development and production. Recently, microRNAs (miRNAs) have been found to be involved in several plant processes such as growth regulation and stress responses. In this study, miRNAs associated with boron stress were identified and characterized in barley. miRNA profiles were also comparatively analyzed between root and leave samples. A total of 31 known and 3 new miRNAs were identified in barley; 25 of them were found to respond to boron treatment. Several miRNAs were expressed in a tissue specific manner; for example, miR156d, miR171a, miR397, and miR444a were only detected in leaves. Additionally, a total of 934 barley transcripts were found to be specifically targeted and degraded by miRNAs. In silico analysis of miRNA target genes demonstrated that many miRNA targets are conserved transcription factors such as Squamosa promoter-binding protein, Auxin response factor (ARF), and the MYB transcription factor family. A majority of these targets were responsible for plant growth and response to environmental changes. We also propose that some of the miRNAs in barley such as miRNA408 might play critical roles against boron exposure. In conclusion, barley may use several pathways and cellular processes targeted by miRNAs to cope with boron stress.

硼胁迫是影响植物生长发育与产量的环境胁迫因子。近年来，研究发现微小RNA（microRNAs, miRNAs）参与诸多植物生理过程，包括生长调控与胁迫应答。本研究对大麦中与硼胁迫相关的miRNAs进行了鉴定与特征分析，并对根、叶样本中的miRNA表达谱开展了比较研究。本研究共在大麦中鉴定出31个已知miRNA与3个全新miRNA，其中25个可响应硼处理。部分miRNA呈现组织特异性表达模式：例如miR156d、miR171a、miR397及miR444a仅在叶片中被检测到。此外，共发现934个大麦转录本可被特定miRNA靶向并降解。对miRNA靶基因的生物信息学分析显示，诸多miRNA靶基因为保守转录因子，如Squamosa启动子结合蛋白、生长素响应因子（Auxin response factor, ARF）以及MYB转录因子家族。此类靶基因大多参与植物生长发育与环境胁迫应答过程。本研究同时提出，大麦中部分miRNA（如miR408）可能在抵御硼胁迫过程中发挥关键调控作用。综上，大麦可通过miRNA调控的多条通路与细胞过程来应对硼胁迫。