State Key Lab of Plant Genomics, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China.
Mol Plant. 2013 Nov;6(6):1830-48. doi: 10.1093/mp/sst087. Epub 2013 May 29.
Ethylene plays essential roles in adaptive growth of rice plants in water-saturating environment; however, ethylene signaling pathway in rice is largely unclear. In this study, we report identification and characterization of ethylene-response mutants based on the specific ethylene-response phenotypes of etiolated rice seedlings, including ethylene-inhibited root growth and ethylene-promoted coleoptile elongation, which is different from the ethylene triple-response phenotype in Arabidopsis. We establish an efficient system for screening and a set of rice mutants have been identified. Genetic analysis reveals that these mutants form eight complementation groups. All the mutants show insensitivity or reduced sensitivity to ethylene in root growth but exhibit differential responses in coleoptile growth. One mutant group mhz7 has insensitivity to ethylene in both root and coleoptile growth. We identified the corresponding gene by a map-based cloning method. MHZ7 encodes a membrane protein homologous to EIN2, a central component of ethylene signaling in Arabidopsis. Upon ethylene treatment, etiolated MHZ7-overexpressing seedlings exhibit enhanced coleoptile elongation, increased mesocotyl growth and extremely twisted short roots, featuring enhanced ethylene-response phenotypes in rice. Grain length was promoted in MHZ7-transgenic plants and 1000-grain weight was reduced in mhz7 mutants. Leaf senescent process was also affected by MHZ7 expression. Manipulation of ethylene signaling may improve adaptive growth and yield-related traits in rice.
乙烯在水饱和环境中对水稻植株的适应性生长起着至关重要的作用；然而，水稻中的乙烯信号通路在很大程度上还不清楚。在这项研究中，我们根据水稻幼苗的特定乙烯反应表型，包括乙烯抑制根生长和乙烯促进胚芽鞘伸长，鉴定并描述了乙烯反应突变体，这与拟南芥中的乙烯三重反应表型不同。我们建立了一种有效的筛选系统，并鉴定出了一组水稻突变体。遗传分析表明，这些突变体形成了八个互补群。所有突变体在根生长中对乙烯表现出不敏感或敏感性降低，但在胚芽鞘生长中表现出不同的反应。一个突变体组 mhz7 在根和胚芽鞘生长中对乙烯均不敏感。我们通过图谱定位克隆方法鉴定了相应的基因。MHZ7 编码一种膜蛋白，与拟南芥乙烯信号中的核心成分 EIN2 同源。在乙烯处理后，暗培养的 MHZ7 过表达幼苗表现出增强的胚芽鞘伸长、增加的中胚轴生长和极度扭曲的短根，表现出增强的水稻乙烯反应表型。MHZ7 转基因植株的粒长增加，mhz7 突变体的千粒重降低。叶片衰老过程也受到 MHZ7 表达的影响。乙烯信号的操纵可能会改善水稻的适应性生长和产量相关性状。
