Christopher D A, Hoffer P H
Department of Plant Molecular Physiology, University of Hawaii at Manoa, Honolulu 96822, USA.
Plant J. 1998 Apr;14(1):1-11. doi: 10.1046/j.1365-313x.1998.00078.x.
The chloroplast psbD-psbC loci, which encode the D2 and CP43 subunits of the photosystem II reaction center, respectively, are regulated by a blue light-responsive promoter (BLRP). It has recently been shown in barley seedlings that activation of psbD-psbC transcription by blue light involves inhibition of a protein kinase that represses the BLRP in the dark. To elucidate further the photosensory pathways regulating the psbD BLRP, the effects of three nuclear mutations on the expression of the BLRP in chloroplasts of Arabidopsis thaliana were examined. The mutants used included the det1-1 and det1-6 alleles for the nuclear protein DET1, involved in repressing photomorphogenesis, and the cry1 gene for the blue light photoreceptor, cryptochrome (CRY1), involved in hypocotyl elongation. The BLRP was not significantly expressed in cotyledons of light-grown wild-type seedlings, unlike the light-responsive expression of the chloroplast, psbA and rbcL, and nuclear, Lhcb and Chs, genes. Analysis of the mutants revealed that DET1 represses transcription from the BLRP in a developmental and tissue-specific manner, which is unique from the effects that DET1 has on other light-regulated promoters. In addition, the cry1 mutation did not reduce the expression of the BLRP in response to blue light. This suggests that the BLRP is regulated by a different photosensory system relative to CRY1. A model is proposed involving blue light, DET1 and phytochrome in regulating transcription from the psbD BLRP.
叶绿体的psbD-psbC基因座分别编码光系统II反应中心的D2和CP43亚基，受蓝光响应启动子（BLRP）调控。最近在大麦幼苗中发现，蓝光对psbD-psbC转录的激活涉及对一种蛋白激酶的抑制，该蛋白激酶在黑暗中抑制BLRP。为了进一步阐明调节psbD BLRP的光感受途径，研究了三个核突变对拟南芥叶绿体中BLRP表达的影响。所使用的突变体包括参与抑制光形态建成的核蛋白DET1的det1-1和det1-6等位基因，以及参与下胚轴伸长的蓝光光感受器隐花色素（CRY1）的cry1基因。与叶绿体的psbA、rbcL以及核基因Lhcb和Chs的光响应表达不同，BLRP在光照下生长的野生型幼苗子叶中未显著表达。对突变体的分析表明，DET1以发育和组织特异性方式抑制BLRP的转录，这与DET1对其他光调节启动子的作用不同。此外，cry1突变并未降低蓝光响应下BLRP的表达。这表明BLRP受与CRY1不同的光感受系统调控。提出了一个涉及蓝光、DET1和光敏色素调节psbD BLRP转录的模型。
