Department of Botany, University of Leicester, LE1 7RH, Leicester, UK.
Planta. 1992 Sep;188(2):173-81. doi: 10.1007/BF00216811.
A comparison of the photoregulation of development has been made for etiolated and light-grown plants of wild-type (WT) tobacco (Nicotiana tabacun L.) and an isogenic transgenic line which expresses an introduced oat phytochrome gene (phyA) under the control of a constitutive viral promoter. Etiolated seedlings of both the WT and transgenic line showed irradiance-dependent inhibition of hypocotyl growth under continuous far-red (FR) light; transgenic seedlings showed a greater level of inhibition under a given fluence rate and this is considered to be the result of the heterologous phytochrome protein (PhyA) functioning in a compatible manner with the native etiolated phytochrome. Deetiolation of WT seedlings resulted in a loss of responsiveness to prolonged FR. Light-grown transgenic seedlings, however, continued to respond in an irradiance-dependent manner to prolonged FR and it is proposed that this is a specific function of the constitutive PhyA. Mature green plants of the WT and transgenic lines showed a qualitatively similar growth promotion to a brief end-of-day FR-treatment but this response was abolished in the transgenic plants under prolonged irradiation by this same FR source. Growth inhibition (McCormac et al. 1991, Planta 185, 162-170) and enhanced levels of nitrate-reductase activity under irradiance of low red:far-red ratio, as achieved by the FR-supplementation of white light, emphasised that the introduced PhyA was eliciting an aberrant mode of photoresponse compared with the normal phytochrome population of light-grown plants. Total levels of the oat-encoded phytochrome in the etiolated transgenic tobacco were shown to be influenced by the wavelength of continuous irradiation in a manner which was qualitatively similar to that seen for the native, etiolated tobacco phytochrome, and distinct from that seen in etiolated oat tissues. These results are discussed in terms of the proposal that the constitutive oat-PhyA pool in the transgenic plants leads to a persistence of a mode of response normally restricted to the situation in etiolated plants.
对野生型（WT）烟草（Nicotiana tabacun L.）和表达在组成型病毒启动子控制下的引入的燕麦光敏素基因（phyA）的同基因转基因系的光生长和黄化植物的发育的光调节进行了比较。WT 和转基因系的黄化幼苗在连续远红光（FR）下均表现出下胚轴生长的辐照度依赖性抑制；在给定的辐照度下，转基因幼苗表现出更高水平的抑制，这被认为是异源光敏素蛋白（PhyA）以与天然黄化光敏素相容的方式起作用的结果。WT 幼苗的脱黄化导致对长时间 FR 的反应性丧失。然而，光生长的转基因幼苗继续以辐照度依赖性的方式对长时间 FR 作出反应，据提议，这是组成型 PhyA 的特定功能。WT 和转基因系的成熟绿色植物对短暂的末端 FR 处理表现出类似的生长促进作用，但在相同 FR 源的长时间照射下，这种反应在转基因植物中被消除。在低红光：远红光比值的光照下生长抑制（McCormac 等人，1991 年，Planta 185，162-170）和硝酸还原酶活性的增强，如通过白光的 FR 补充实现，强调了引入的 PhyA 与光生长植物的正常光敏素群体相比，引发了异常的光反应模式。黄化转基因烟草中燕麦编码的光敏素的总水平被证明受到连续照射波长的影响，这种方式与天然黄化烟草光敏素的方式相似，与黄化燕麦组织的方式不同。这些结果根据组成型燕麦-PhyA 池在转基因植物中导致一种通常仅限于黄化植物情况的反应模式的持续存在的提议进行了讨论。
