Unlike in metazoans, the stepwise biogenesis of microRNAs (miRNAs) in plants occurs within the nucleus. Whether or how the major steps in miRNA biogenesis are coordinated is largely unknown. Here we show that the plant TREX-2 complex promotes multiple steps in miRNA biogenesis, including transcription, processing and nuclear export. THP1 and SAC3A—the core subunits of TREX-2—interact and colocalize with RNA polymerase II to promote the transcription of MIR genes in the nucleoplasm. TREX-2 interacts with the microprocessor component SERRATE and promotes the formation of dicing bodies in the nucleoplasm. THP1 also interacts and colocalizes with the nucleoporin protein NUP1 at the nuclear envelope. NUP1 and THP1 promote the nuclear export of miRNAs and ARGONAUTE1. These results suggest that TREX-2 coordinates the transcription, processing and export steps in miRNA biogenesis to ensure efficient miRNA production.

与后生动物不同，植物中的microRNA（miRNA）逐步生物发生在细胞核内。miRNA生物发生的主要步骤是否协调或如何协调，目前尚不清楚。在这里，我们表明植物TREX-2复合物促进miRNA生物发生的多个步骤，包括转录，加工和核输出。THP1和SAC3A（TREX-2的核心亚基）与RNA聚合酶II相互作用并共定位以促进MIR的转录核质中的基因。TREX-2与微处理器组件SERRATE相互作用，并促进核质中切割体的形成。THP1还在核被膜处与核孔蛋白NUP1相互作用并共定位。NUP1和THP1促进miRNA和ARGONAUTE1的核输出。这些结果表明TREX-2协调miRNA生物发生中的转录，加工和输出步骤，以确保有效的miRNA生产。