Yamauchi Y, Fukaki H, Fujisawa H, Tasaka M
Department of Botany, Graduate School of Science, Kyoto University, Japan.
Plant Cell Physiol. 1997 May;38(5):530-5. doi: 10.1093/oxfordjournals.pcp.a029201.
Shoots of higher plants grow upward in response to gravity. To elucidate the molecular mechanism of this response, we have isolated shoot gravitropism (sgr) mutants in Arabidopsis thaliana. In this report, we describe three novel mutants, sgr4-1, sgr5-1 and sgr6-1 whose inflorescence stems showed abnormal gravitropic responses as previously reported for sgr1, sgr2 and sgr3. These new sgr mutations were recessive and occurred at three independent genetic loci. The sgr4-1 mutant showed severe defect in gravitropism of both inflorescence stem and hypocotyl but were normal in root gravitropism as were sgr1 and sgr2. The sgr5-1 and sgr6-1 mutants showed reduced gravitropism only in inflorescence stems but normal in both hypocotyls and roots as sgr3. These results support the hypothesis that some mechanisms of gravitropism are genetically different in these three organs in A. thaliana. In addition, these mutants showed normal phototropic responses, suggesting that SGR4, SGR5 and SGR6 genes are specifically involved in gravity perception and/or gravity signal transduction for the shoot gravitropic response.
高等植物的茎会因重力作用向上生长。为了阐明这种反应的分子机制，我们在拟南芥中分离出了茎向重力性（sgr）突变体。在本报告中，我们描述了三个新的突变体，sgr4-1、sgr5-1和sgr6-1，它们的花序茎表现出异常的向重力性反应，正如之前报道的sgr1、sgr2和sgr3那样。这些新的sgr突变是隐性的，且发生在三个独立的基因位点。sgr4-1突变体在花序茎和下胚轴的向重力性方面表现出严重缺陷，但在根的向重力性方面正常，sgr1和sgr2也是如此。sgr5-1和sgr6-1突变体仅在花序茎中表现出向重力性降低，而在下胚轴和根中正常，sgr3也是如此。这些结果支持了这样一种假说，即拟南芥这三个器官中向重力性的某些机制在遗传上是不同的。此外，这些突变体表现出正常的向光性反应，表明SGR4、SGR5和SGR6基因特别参与了茎向重力性反应的重力感知和/或重力信号转导。
