Yanovsky M J, Casal J J, Luppi J P
Departamento de Ecología, Facultad de Agronomía, Universidad de Buenos Aires, Argentina.
Plant J. 1997 Sep;12(3):659-67. doi: 10.1046/j.1365-313x.1997.00659.x.
Phytochromes play a key role in the perception of light signals by plants. In this study, the three classical phytochrome action modes, i.e. very-low-fluence responses (VLFR), low-fluence responses (LFR) and high-irradiance responses (HIR), were genetically dissected using phyA and phyB mutants of Arabidopsis thaliana (respectively lacking phytochrome A or phytochrome B) and a polymorphism between ecotypes Landsberg erecta and Columbia. Seed germination and potentiation of greening, hypocotyl growth inhibition and cotyledon unfolding in etiolated seedlings of the ecotype Landsberg erecta showed biphasic responses to the calculated proportion of active phytochrome established by one light pulse or repeated light pulses. The first phase, i.e. the VLFR, was absent in the phyA mutant, normal in the phyB mutant (both in the Landsberg erecta background) and severely deficient in Columbia. The second phase, i.e. the LFR, was present in the phyA mutant, deficient in the phyB mutant and normal in Columbia. Under continuous far-red light, HIR of etiolated seedlings were absent in phyA and normal in phyB and Columbia. The segregation of VLFR in recombinant inbred lines derived from a cross between Landsberg erecta and Columbia was analysed by MAPMAKER/QTL. Two quantitative trait loci, one on chromosome 2 (VLF1) and another on chromosome 5 (VLF2), were identified as responsible for the polymorphism. Phytochrome A is proposed to initiate two transduction pathways, VLFR and HIR, involving different cells and/or different molecular steps. This is the first application of the analysis of quantitative trait loci polymorphic between ecotypes to dissect transduction chains of environmental signals.
光敏色素在植物感知光信号过程中起关键作用。在本研究中，利用拟南芥的phyA和phyB突变体（分别缺失光敏色素A或光敏色素B）以及生态型Landsberg erecta和Columbia之间的多态性，对三种经典的光敏色素作用模式，即极低光通量反应（VLFR）、低光通量反应（LFR）和高辐照度反应（HIR）进行了遗传学剖析。生态型Landsberg erecta黄化幼苗的种子萌发及绿化增强、下胚轴生长抑制和子叶展开对一个光脉冲或重复光脉冲所建立的活性光敏色素计算比例表现出双相反应。第一阶段，即VLFR，在phyA突变体中缺失，在phyB突变体中正常（均为Landsberg erecta背景），在Columbia中严重缺陷。第二阶段，即LFR，在phyA突变体中存在，在phyB突变体中缺陷，在Columbia中正常。在连续远红光下，phyA突变体中黄化幼苗的HIR缺失，phyB突变体和Columbia中正常。利用MAPMAKER/QTL分析了Landsberg erecta和Columbia杂交产生的重组自交系中VLFR的分离情况。确定了两个数量性状位点，一个位于2号染色体上（VLF1），另一个位于5号染色体上（VLF2），它们导致了这种多态性。推测光敏色素A启动两条转导途径，即VLFR和HIR，涉及不同的细胞和/或不同的分子步骤。这是首次应用生态型间数量性状位点多态性分析来剖析环境信号转导链。
