Bao Maolin, Bian Hongwu, Zha Yulong, Li Fengyun, Sun Yuzhe, Bai Bin, Chen Zhehao, Wang Junhui, Zhu Muyuan, Han Ning
Key Laboratory for Cell and Gene Engineering of Zhejiang Province, Institute of Genetics, College of Life Sciences, Zhejiang University, Hangzhou 310058, Zhejiang, China.
Key Laboratory for Cell and Gene Engineering of Zhejiang Province, Institute of Genetics, College of Life Sciences, Zhejiang University, Hangzhou 310058, Zhejiang, ChinaCollege of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou, 310036, Zhejiang, China.
Plant Cell Physiol. 2014 Jul;55(7):1343-53. doi: 10.1093/pcp/pcu058. Epub 2014 May 3.
miR396 targets seven GROWTH-REGULATING FACTOR (GRF) genes and the BASIC HELIX-LOOP-HELIX (bHLH) TRANSCRIPTION FACTOR 74 gene (bHLH74) in Arabidopsis. Previous research revealed that the miR396 target module regulates cell proliferation and plays a critical role in leaf development. However, no additional biological functions of miR396 have been investigated in detail. In this study, T-DNA insertion mutants and transgenic plants with altered levels of miR396 or its target genes were used to characterize the regulatory role of miR396 in root development. We found that AtMIR396a was the predominant source for miR396 accumulation in the roots of seedlings, and that the mir396a-1 mutant had longer roots than wild-type seedlings. Overexpression of AtMIR396a decreased the transcript levels of target genes such as GRF genes and bHLH74, and resulted in a shorter root phenotype. Furthermore, the bhlh74-1 mutant had shorter roots, whereas overexpression of an miR396-resistant form of bHLH74 (mbHLH74) had an enhanced root growth phenotype. Moreover, MIR396a regulated root growth by affecting the elongation zone. Taken together, these data indicate that miR396a-mediated bHLH74 repression helps regulate root growth in Arabidopsis seedlings.
在拟南芥中，miR396靶向7个生长调节因子（GRF）基因以及碱性螺旋-环-螺旋（bHLH）转录因子74基因（bHLH74）。先前的研究表明，miR396靶标模块调控细胞增殖，并在叶片发育中起关键作用。然而，miR396的其他生物学功能尚未得到详细研究。在本研究中，利用T-DNA插入突变体以及miR396或其靶基因水平发生改变的转基因植物，来表征miR396在根发育中的调控作用。我们发现，AtMIR396a是幼苗根中miR396积累的主要来源，并且mir396a-1突变体的根比野生型幼苗的根更长。AtMIR396a的过表达降低了GRF基因和bHLH74等靶基因的转录水平，并导致根表型变短。此外，bhlh74-1突变体的根较短，而抗miR396形式的bHLH74（mbHLH74）的过表达则具有增强的根生长表型。此外，MIR396a通过影响伸长区来调节根的生长。综上所述，这些数据表明miR396a介导的对bHLH74的抑制有助于调节拟南芥幼苗的根生长。
