THE SIGNIFICANCE OF MICROSPORE DIVISION AND DIVISION SYMMETRY FOR VEGETATIVE CELL-SPECIFIC TRANSCRIPTION AND GENERATIVE CELL-DIFFERENTIATION
THE SIGNIFICANCE OF MICROSPORE DIVISION AND DIVISION SYMMETRY FOR VEGETATIVE CELL-SPECIFIC TRANSCRIPTION AND GENERATIVE CELL-DIFFERENTIATION
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DOI：
10.1105/tpc.7.1.65
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发表时间：
1995-01-01
期刊：
影响因子：
11.6
通讯作者：
TWELL, D
中科院分区：
文献类型：
--
作者：
EADY, C;LINDSEY, K;TWELL, D
通过转基因烟草小孢子的体外成熟实验，研究了花粉有丝分裂I(PMI)的开始和对称性对营养细胞和生殖细胞随后分化的意义。含有营养细胞(Vc)特异的晚花药番茄lat52启动子与β-葡萄糖醛酸酶(GUS)基因融合的转基因植株的游离单核小孢子在PMI时表现出正常的不对称细胞分裂，并在体外成熟过程中激活了Vc中特异的Lat52启动子。在高水平秋水仙素存在下的体外成熟有效地阻断了PMI，导致了单核花粉粒的形成，其中LAT52启动子被激活。此外，成熟的单核花粉粒在没有功能生殖细胞(GC)的情况下仍能萌发和花粉管生长。较低水平的秋水仙素诱导PMI的对称分裂，产生两个相似的子细胞，防止典型的GC染色质凝聚，类似的含有Lat52启动子的转基因小孢子培养结果表明，Lat52启动子在两个对称子细胞中都发生了激活。这些结果直接证明了PMI的分裂不对称对于正确的GC分化是必不可少的，并且VC特异转录的激活和功能性VC的成熟可能与PMI的胞质分裂解偶联。这些结果与提出的模型有关，这些模型解释了控制营养细胞和生殖细胞不同命运的因素的作用和分布。
The significance of the onset and symmetry of pollen mitosis I (PMI) for the subsequent differentiation of the vegetative and generative cells was investigated by the in vitro maturation of isolated microspores of transgenic tobacco. Free uninucleate microspores of transgenic plants harboring the vegetative cell (VC)-specific late anther tomato lat52 promoter fused to the beta-glucuronidase (gus) gene showed normal asymmetric cell division at PMI and activated the lat52 promoter specifically in the nascent VC during in vitro maturation. In vitro maturation in the presence of high levels of colchicine effectively blocked PMI, resulting in the formation of uninucleate pollen grains in which the lat52 promoter was activated. Furthermore, matured uninucleate pollen grains were capable of germination and pollen tube growth despite the absence of a functional generative cell (GC). Lower levels of colchicine induced symmetric division at PMI, producing two similar daughter cells in which typical GC chromatin condensation was prevented, Similar cultures of transgenic microspores harboring the lat52 promoter driving the expression of a nuclear-targeted GUS fusion protein showed that lat52 promoter activation occurred in both symmetric daughter cells. These results directly demonstrate that division asymmetry at PMI is essential for correct GC differentiation and that activation of VC-specific transcription and functional VC maturation may be uncoupled from cytokinesis at PMI. These results are discussed in relation to models proposed to account for the role and distribution of factors controlling the differing fates of the vegetative and generative cells.