Regulation of auxin response by miR393-targeted transport inhibitor response protein 1 is involved in normal development in Arabidopsis
miR393, which is encoded by MIR393a and MIR393b in Arabidopsis, post-transcriptionally regulates mRNAs for the F-box auxin receptors TIR1 (Transport Inhibitor Response Protein 1), AFB1 (Auxin Signaling F-box Protein 1), AFB2 and AFB3. However, biological functions of the miR393-TIR1/AFBs module in auxin response and plant development is not fully understood. In the study herein, we demonstrate that miR393 accumulated in response to exogenous IAA treatment, and its induction was due to enhanced MIR393b transcription but not MIR393a. Overexpression of a miR393-resistant form of TIR1 (mTIR1) enhanced auxin sensitivity and led to pleiotropic effects on plant development including inhibition of primary root growth, overproduction of lateral roots, altered leave phenotype and delayed flowering. Furthermore, miR393 level was increased in 35S:mTIR1 plant, suggesting that TIR1 promoted the expression of miR393 by a feedback loop. The interaction between miR393 and its target indicates a fine adjustment to the roles of the miR393-TIR1 module, which is required for auxin responses in plant development.
KeywordsmicroRNAs miR393 Transport inhibitor response 1 (TIR1) Auxin response Development Arabidopsis thaliana
We sincerely thank Dr. Mark Estelle (Section of Cell and Developmental Biology, UCSD) for kindly providing the tir1-1 and tir1-1 afb1-1 afb2-1 afb3-1 quadruple mutants and Dr. C-Y Huang (The University of Adelaide, Australia) for helpful discussions and critical reading the manuscript. This work was supported by the National Science Foundation of China (Grant No. 30571197, No. 30972016), National High Technology Research and Development Program of China (863 Program) (No. 2007AA10Z141) and Zhejiang Provincial Natural Science Foundation of China (Grant No. Y3080323).
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