Xu Lin, Yang Li, Pi Limin, Liu Qili, Ling Qihua, Wang Hua, Poethig R Scott, Huang Hai
National Laboratory of Plant Molecular Genetics, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, 300 Fenglin Road, Shanghai 200032, PR China.
Plant Cell Physiol. 2006 Jul;47(7):853-63. doi: 10.1093/pcp/pcj057. Epub 2006 May 13.
In higher plants, class I KNOTTED1-like homeobox (KNOX) gene suppression and leaf polarity establishment are two processes crucial for leaf morphogenesis. The Arabidopsis genes, ASYMMETRIC LEAVES1 and 2 (AS1 and AS2), are required for repressing the class I KNOX genes and promoting leaf adaxial cell fates. In addition, the RNA-DEPENDENT RNA POLYMERASE6 (RDR6) gene acts synergistically with AS1 and AS2 to specify the adaxial polarity and repress the KNOX genes in leaves. It is known that RDR6 is one of the key components in plant post-transcriptional gene silencing (PTGS), and is likely to function with other silencing components in a genetic pathway in regulating leaf patterning. Here we report phenotypic analyses of double mutants combining as1 or as2 with other mutations relating to different RNA silencing pathways. We show that plants carrying rdr6, suppressor of gene silencing3 (sgs3) or zippy (zip, also called ago7) in combination with as1 or as2 demonstrate severe morphological defects, and the double mutant plants are generally similar to one another. Detailed phenotypic and molecular analyses reveal that leaves of rdr6 as2(1), sgs3 as2(1) and zip as2(1) all show an abnormal adaxial identity, and contain high levels of microRNA165/166 and FILAMENTOUS FLOWER (FIL) transcripts. These results suggest that RDR6, SGS3 and AGO7 act in the same pathway, which genetically interacts with the AS1-AS2 pathway for leaf development. The RDR6-SGS3-AGO7 pathway was previously identified as regulating the plant vegetative phase change. Our results reveal a new function of the pathway, which is also required for normal leaf morphogenesis.
在高等植物中，I类KNOTTED1同源异型框（KNOX）基因抑制和叶片极性建立是叶片形态发生的两个关键过程。拟南芥基因ASYMMETRIC LEAVES1和2（AS1和AS2）对于抑制I类KNOX基因和促进叶片近轴细胞命运是必需的。此外，RNA依赖性RNA聚合酶6（RDR6）基因与AS1和AS2协同作用，以确定近轴极性并抑制叶片中的KNOX基因。已知RDR6是植物转录后基因沉默（PTGS）的关键成分之一，并且可能在调节叶片模式的遗传途径中与其他沉默成分一起发挥作用。在这里，我们报告了将as1或as2与其他与不同RNA沉默途径相关的突变相结合的双突变体的表型分析。我们表明，携带rdr6、基因沉默抑制子3（sgs3）或zippy（zip，也称为ago7）与as1或as2组合的植物表现出严重的形态缺陷，并且双突变体植物通常彼此相似。详细的表型和分子分析表明，rdr6 as2(1)、sgs3 as2(1)和zip as2(1)的叶片均显示出异常的近轴特征，并且含有高水平的microRNA165/166和丝状花（FIL）转录本。这些结果表明，RDR6、SGS3和AGO7在同一途径中起作用，该途径在遗传上与AS1-AS2途径相互作用以促进叶片发育。RDR6-SGS3-AGO7途径先前被确定为调节植物营养阶段转变。我们的结果揭示了该途径的新功能，这也是正常叶片形态发生所必需的。
