Johnson E M, Pao L I, Feldman L J
Department of Plant Biology, University of California, Berkeley 94720, USA.
Plant Physiol. 1991;95(2):544-50. doi: 10.1104/pp.95.2.544.
In many cultivars of maize (Zea mays L.) red light affects root development via the photomorphogenetic pigment phytochrome. The site of perception for the light is the root cap. In the maize cultivar Merit, we investigated phytochrome-mediated events in the cap. We established that the message encoded by the phyA1 gene was most abundant in dark-grown tissue and was asymmetrically distributed in the root cap, with greatest expression in the cells which make up the central columella core of the cap. Phytochrome message was negatively autoregulated in a specific region within the root cap. This autoregulation was sensitive to very-low-fluence red light, and thus was characterized as a phytochrome-mediated, very-low-fluence event. The kinetics of message reaccumulation in the dark were also examined and compared to the kinetics of the light requirement for root gravitropism in this cultivar. Similarly, the degree of autoregulation present in two other maize cultivars with different light requirements for gravitropic sensitivity was investigated. It appears that the Merit cultivar expresses a condition of hypersensitivity to phytochrome-mediated light regulation in root tissues. We conclude that phytochrome regulates many activities within the cap, but the degree to which these activities share common phytochrome-mediated steps is not known.
在许多玉米（Zea mays L.）品种中，红光通过光形态建成色素光敏色素影响根系发育。光的感知部位是根冠。在玉米品种“优点”中，我们研究了光敏色素在根冠中介导的事件。我们确定，phyA1基因编码的信息在黑暗生长的组织中最为丰富，且在根冠中呈不对称分布，在构成根冠中央柱心的细胞中表达量最高。光敏色素信息在根冠内的特定区域受到负向自我调节。这种自我调节对极低光通量的红光敏感，因此被表征为一种光敏色素介导的极低光通量事件。还研究了黑暗中信息重新积累的动力学，并与该品种根系向地性对光的需求动力学进行了比较。同样，研究了另外两个对向地性敏感性有不同光照需求的玉米品种中存在的自我调节程度。看来“优点”品种在根组织中表现出对光敏色素介导的光调节超敏感的状态。我们得出结论，光敏色素调节根冠内的许多活动，但这些活动共享共同的光敏色素介导步骤的程度尚不清楚。
