Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE-90183 Umeå, Sweden.
Plant Cell. 2009 Oct;21(10):3119-32. doi: 10.1105/tpc.108.064758. Epub 2009 Oct 9.
The development of shoot-borne roots, or adventitious roots, is indispensable for mass propagation of elite genotypes. It is a complex genetic trait with a high phenotypic plasticity due to multiple endogenous and environmental regulatory factors. We demonstrate here that a subtle balance of activator and repressor AUXIN RESPONSE FACTOR (ARF) transcripts controls adventitious root initiation. Moreover, microRNA activity appears to be required for fine-tuning of this process. Thus, ARF17, a target of miR160, is a negative regulator, and ARF6 and ARF8, targets of miR167, are positive regulators of adventitious rooting. The three ARFs display overlapping expression domains, interact genetically, and regulate each other's expression at both transcriptional and posttranscriptional levels by modulating miR160 and miR167 availability. This complex regulatory network includes an unexpected feedback regulation of microRNA homeostasis by direct and nondirect target transcription factors. These results provide evidence of microRNA control of phenotypic variability and are a significant step forward in understanding the molecular mechanisms regulating adventitious rooting.
茎生根（不定根）的发育对于优质基因型的大规模繁殖是必不可少的。这是一个复杂的遗传性状，由于多种内源性和环境调节因子的存在，具有高度的表型可塑性。我们在这里证明，激活子和抑制剂 AUXIN RESPONSE FACTOR（ARF）转录本的微妙平衡控制着不定根的起始。此外，miRNA 的活性似乎是精细调控这一过程所必需的。因此，miR160 的靶标 ARF17 是一个负调节剂，而 miR167 的靶标 ARF6 和 ARF8 是不定根形成的正调节剂。这三个 ARF 在转录和转录后水平上通过调节 miR160 和 miR167 的可用性相互作用，并相互调节对方的表达，从而表现出重叠的表达区域。这个复杂的调控网络包括通过直接和非直接靶转录因子对 miRNA 动态平衡的意外反馈调控。这些结果为 miRNA 对表型可变性的控制提供了证据，并且是理解调节不定根形成的分子机制的重要一步。
