Park Soon Ki, Rahman Daisy, Oh Sung Aeong, Twell David
Department of Biology, University of Leicester, University Road, Leicester LE1 7RH, UK.
Sex Plant Reprod. 2004 May 26;17(2):63-70. doi: 10.1007/s00497-004-0216-x.
Gametophytic cytokinesis is essential for the development and function of the male and female gametophytes. We have previously described the isolation and characterisation of the gemini pollen 1 (gem1) that acts gametophytically to disturb asymmetric division and cytokinesis at pollen mitosis I in Arabidopsis. Here we describe the genetic and cytological analysis of an independent gametophytic mutant, gem2, with similar characteristics to gem1, but which maps to a different genetic locus. gem2 shows reduced genetic transmission through both male and female gametes and leads to the production of divided or twin-celled pollen. Developmental analysis revealed that gem2 does not affect karyokinesis at pollen mitosis I, but leads to repositioning of the cell plate and partial or complete failure of cytokinesis, resulting in symmetrical divisions or binucleate pollen grains respectively. Symmetrical divisions lead to altered pollen cell fate with both sister cells displaying vegetative cell fate. Moreover, we demonstrate that the predominant female defect in gem2 is a lack of cellularization of the embryo sac during megagametogenesis. GEM2 therefore defines an independent genetic locus that is involved in the correct specification of both male and female gametophytic cytokinesis.
配子体胞质分裂对于雄配子体和雌配子体的发育及功能至关重要。我们之前描述了双子叶花粉1（gem1）的分离和特性，它在配子体水平上干扰拟南芥花粉有丝分裂I时的不对称分裂和胞质分裂。在此，我们描述了一个独立的配子体突变体gem2的遗传和细胞学分析，它与gem1具有相似的特征，但定位在不同的基因座上。gem2通过雄配子和雌配子的遗传传递均减少，并导致产生分裂的或双细胞花粉。发育分析表明，gem2不影响花粉有丝分裂I时的核分裂，但会导致细胞板重新定位以及胞质分裂部分或完全失败，分别导致对称分裂或双核花粉粒。对称分裂导致花粉细胞命运改变，两个姐妹细胞均表现出营养细胞命运。此外，我们证明gem2中主要的雌性缺陷是大孢子发生过程中胚囊缺乏细胞化。因此，GEM2定义了一个独立的基因座，该基因座参与雄配子体和雌配子体胞质分裂的正确调控。
