Marri Lucia, Sparla Francesca, Pupillo Paolo, Trost Paolo
Laboratory of Molecular Plant Physiology, Department of Biology, University of Bologna, Via Irnerio 42, I-40126 Bologna, Italy.
J Exp Bot. 2005 Jan;56(409):73-80. doi: 10.1093/jxb/eri020. Epub 2004 Nov 8.
Photosynthetic glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and phosphoribulokinase (PRK) interact in the chloroplast stroma through the action of the small peptide CP12. This supramolecular complex concurs with the light-dependent modulation in vivo of GAPDH and PRK activities. The expression patterns of several genes potentially involved in the formation of the complex have been studied. The genome of Arabidopsis thaliana includes seven genes for phosphorylating GAPDH isozymes, one PRK gene, and three genes for CP12. The expression of four GAPDH genes was analysed, i.e. GapA-1 and GapB for photosynthetic GAPDH of chloroplasts (NAD(P)-dependent), GapC-1 for cytosolic GAPDH, and GapCp-1 for plastid GAPDH (both NAD-dependent). A similar analysis was performed with PRK and two CP12 genes (CP12-1, CP12-2). The expression of GapA-1, GapB, PRK, and CP12-2 was found to be co-ordinately regulated with the same organ specificity, all four genes being mostly expressed in leaves and flower stalks, less expressed in flowers, and little or not expressed in roots and siliques. The expression of all these genes in leaves was terminated during prolonged darkness or following sucrose treatments, and their transcripts decayed with similar kinetics. At variance with CP12-2, gene CP12-1 appeared to be expressed more in flowers, it was totally insensitive to darkness, and less affected by sucrose. The expression of glycolytic GapC was strong and ubiquitous, insensitive to dark treatments, and unaffected by sucrose. GapCp transcripts were also found to be ubiquitous at lower levels, slowly decreasing in the dark and stable in sucrose-treated leaves. The co-ordinated expression of genes GapA-1, GapB, PRK, and CP12-2 is consistent with their specific involvement in the formation of the photosynthetic regulatory complex of chloroplasts.
光合甘油醛-3-磷酸脱氢酶（GAPDH）和磷酸核酮糖激酶（PRK）通过小肽CP12的作用在叶绿体基质中相互作用。这种超分子复合物与体内GAPDH和PRK活性的光依赖性调节一致。已经研究了几个可能参与该复合物形成的基因的表达模式。拟南芥基因组包括七个用于磷酸化GAPDH同工酶的基因、一个PRK基因和三个CP12基因。分析了四个GAPDH基因的表达，即叶绿体光合GAPDH（依赖NAD(P)）的GapA-1和GapB、胞质GAPDH的GapC-1以及质体GAPDH（均依赖NAD）的GapCp-1。对PRK和两个CP12基因（CP12-1、CP12-2）进行了类似分析。发现GapA-1、GapB、PRK和CP12-2的表达具有相同的器官特异性协同调节，所有这四个基因主要在叶片和花茎中表达，在花中表达较少，在根和角果中几乎不表达或不表达。在长时间黑暗或蔗糖处理后，所有这些基因在叶片中的表达终止，其转录本以相似的动力学衰减。与CP12-2不同，CP12-1基因在花中的表达似乎更多，它对黑暗完全不敏感，受蔗糖影响较小。糖酵解GapC的表达强烈且普遍存在，对黑暗处理不敏感，不受蔗糖影响。还发现GapCp转录本在较低水平上普遍存在，在黑暗中缓慢减少，在蔗糖处理的叶片中稳定。GapA-1、GapB、PRK和CP12-2基因的协同表达与其在叶绿体光合调节复合物形成中的特定作用一致。
