Boucheron E, Healy J H S, Bajon C, Sauvanet A, Rembur J, Noin M, Sekine M, Riou Khamlichi C, Murray J A H, Van Onckelen H, Chriqui D
Université Pierre et Marie Curie, site Ivry-le Raphaël, Laboratoire CEMV-EA3494, case 150, 4 place Jussieu, F-75252 Paris Cedex 05, France.
J Exp Bot. 2005 Jan;56(409):123-34. doi: 10.1093/jxb/eri001. Epub 2004 Oct 22.
Transgenic tobacco lines expressing Arath-CYCD2 or Arath-CYCD3 genes under a cauliflower mosaic virus 35S promoter are modified in the timing of their development, but not in the phenotype of their vegetative organs. They display an increased rate of leaf initiation, which is shown to be associated with distinct changes in the structural organization of their shoot apical meristem (SAM). Constitutive expression of Arath-CYCD2 leads to a progressive modification of the SAM structural organization with predominant periclinal divisions in the L3 layer and to the loss of the classical cytophysiological zonation, the central zone being reduced to the central cells of the L1 and L2 layers. These changes reveal a particular sensitivity of the corpus cells (L3) to Arath-CYCD2 over-expression and suggest a role for CYCD2 in controlling the planes of cell division in these cells. The SAM structural modifications in the Arath-CYCD3 over-expressing lines are less drastic; only an increased cell number together with a reduced cell size, particularly in the L1 layer, characterizes the peripheral zones. This could be related to the shortening of the G1-phase duration that renders cell growth incomplete between successive mitoses. Cell proliferation continues beyond the SAM in the developing internodes and confers a delayed senescence to Arath-CYCD3 over-expressing juvenile tissues. In addition, the ploidy levels of mature stem tissues in both types of transgenic lines are unaffected, suggesting that the studied G1 to S cell-cycle genes have no effect on the extent of endoreduplication in tobacco stem tissues.
在花椰菜花叶病毒35S启动子控制下表达拟南芥CYCD2或拟南芥CYCD3基因的转基因烟草品系，其发育时间发生了改变，但营养器官的表型未变。它们的叶片起始速率增加，这与茎尖分生组织（SAM）结构组织的明显变化有关。拟南芥CYCD2的组成型表达导致SAM结构组织逐渐改变，L3层主要进行平周分裂，并导致经典细胞生理分区的丧失，中央区缩小为L1和L2层的中央细胞。这些变化揭示了髓细胞（L3）对拟南芥CYCD2过表达具有特殊敏感性，并表明CYCD2在控制这些细胞的细胞分裂平面中发挥作用。拟南芥CYCD3过表达品系中的SAM结构变化不那么剧烈；只有细胞数量增加和细胞大小减小，特别是在L1层，是外周区的特征。这可能与G1期持续时间缩短有关，使得连续有丝分裂之间的细胞生长不完全。在发育中的节间，细胞增殖在SAM之外继续进行，并使拟南芥CYCD3过表达的幼嫩组织衰老延迟。此外，两种转基因品系中成熟茎组织的倍性水平未受影响，这表明所研究的从G1期到S期的细胞周期基因对烟草茎组织的核内复制程度没有影响。
