Wangshu Mou,Ria Khare,Joanna K. Polko,Isaiah Taylor,Juan Xu,Dawei Xue,Philip Benfey,Bram Van de Poel,Caren Chang,Joseph J. Kieber
In seed plants, the canonical role of 1-aminocyclopropane-1-carboxylic acid (ACC) is to serve as the precursor in the biosynthesis of the phytohormone ethylene, and indeed, ACC treatment is often used as a proxy for ethylene treatment. Increasing evidence suggests that ACC can also act independently of ethylene to regulate various aspects of plant growth and development. Here, we explore the effects of ACC on Arabidopsis thaliana root growth and the mechanisms by which it acts. ACC inhibits growth of the primary root in Arabidopsis seedlings when ethylene signaling is blocked, which becomes evident after 36 h of treatment with ACC. This reduced root growth is in part the result of suppressed cell proliferation in the root meristem resulting from altered expression of a key regulator of stem cell niche activity, WOX5. ACC also promotes lateral root (LR) development, in contrast to ethylene, which inhibits LR formation. Transcriptomic analysis of roots revealed no significant changes in gene expression after 45 min or 4 h of ACC treatment, but longer treatment times revealed a large number of differentially expressed genes, including the downregulation of the expression of a small group of phylogenetically related CLE peptides. Reduced expression of these group 1 CLEs in response to ACC leads to the activation of a transcription factor, LBD18, which promotes LR development. These results suggest that ACC acts to modulate multiple aspects of Arabidopsis root growth independently of ethylene via distinct transcriptional effects in the root meristem and LR precursor cells.
Xixi Cai,Hang Zhang,Changqing Mu,Yanjun Chen,Chongzhen He,Mingyu Liu,Thomas Laux,Limin Pi
In multicellular organisms, communication between cells is vital for their fate determination. In plants, the quiescent center (QC) signals to adjacent stem cells to maintain them undifferentiated. However, how surrounding stem cells instruct the QC remains poorly understood. Here, we show that in the Arabidopsis root, microRNA160 (miR160) moves from stele stem cells (SSCs) to the QC, where it degrades the mRNAs of two auxin response factors, ARF10 and ARF17 . This degradation relieves BRAVO from direct transcriptional repression, maintaining QC quiescence. We further identify that blocking miR160 movement due to DNA damage-induced SSC death and restricted symplastic transport reduces BRAVO and WOX5 expression, leading to QC division to replenish damaged stem cells during root regeneration. Together, our results demonstrate that a transcriptional axis initiated by mobile miR160 regulates the QC and stem cell behavior, advancing our understanding of the communication between stem cells and their surrounding cellular environment.
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