Sucrose induction of Arabidopsis miR398 represses two Cu/Zn superoxide dismutases
Sucrose induction of Arabidopsis miR398 represses two Cu/Zn superoxide dismutases
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DOI：
10.1007/s11103-008-9329-1
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发表时间：
2008-07-01
影响因子：
5.1
通讯作者：
Bartel, Bonnie
中科院分区：
文献类型：
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作者：
Dugas, Diana V.;Bartel, Bonnie
微小RNA（miRNAs）类似于21个核苷酸的RNA，它们通过mRNA裂解或翻译抑制来减少靶标积累。拟南芥miR398调节编码两种铜超氧化物歧化酶（CSD）和一种细胞色素c氧化酶亚基的mRNA。miR398自身在铜和胁迫响应中下调。在此我们表明，miR398受蔗糖正向调控，导致CSD1和CSD2的mRNA及蛋白质积累减少。这种蔗糖调控在有和没有生理相关水平的补充铜的情况下均保持。此外，我们表明表达具有改变的miR398互补位点的CSD1和CSD2 mRNA的植物显示mRNA积累增加，而CSD1和CSD2蛋白质积累对miR398水平仍然敏感，这表明当靶位点互补性降低时，miR398可作为翻译抑制因子起作用。这些结果揭示了一种新的miR398调控机制，并证明植物miRNA靶标可以在mRNA水平抵抗miRNA调控，同时在蛋白质积累水平保持敏感性。我们的结果表明，即使在植物中（其中miRNAs被认为主要通过靶mRNA裂解起作用），监测靶蛋白质水平以及靶mRNA水平对于全面评估miRNA - mRNA配对破坏的后果也是必要的。此外，维持对靶蛋白质积累的强大miR398定向抑制所需的有限互补性表明，受类似调控的内源性植物miRNA靶标可能未被检测到。
MicroRNAs (miRNAs) are similar to 21-nt RNAs that reduce target accumulation through mRNA cleavage or translational repression. Arabidopsis miR398 regulates mRNAs encoding two copper superoxide dismutase (CSD) enzymes and a cytochrome c oxidase subunit. miR398 itself is down-regulated in response to copper and stress. Here we show that miR398 is positively regulated by sucrose, resulting in decreased CSD1 and CSD2 mRNA and protein accumulation. This sucrose regulation is maintained both in the presence and absence of physiologically relevant levels of supplemental copper. Additionally, we show that plants expressing CSD1 and CSD2 mRNAs with altered miR398 complementarity sites display increased mRNA accumulation, whereas CSD1 and CSD2 protein accumulation remain sensitive to miR398 levels, suggesting that miR398 can act as a translational repressor when target site complementarity is reduced. These results reveal a novel miR398 regulatory mechanism and demonstrate that plant miRNA targets can resist miRNA regulation at the mRNA level while maintaining sensitivity at the level of protein accumulation. Our results suggest that even in plants, where miRNAs are thought to act primarily through target mRNA cleavage, monitoring target protein levels along with target mRNA levels is necessary to fully assess the consequences of disrupted miRNA-mRNA pairing. Moreover, the limited complementarity required to maintain robust miR398-directed repression of target protein accumulation suggests that similarly regulated endogenous plant miRNA targets may have eluded detection.