Tanaka Hirokazu, Ishikawa Masaki, Kitamura Saori, Takahashi Yuji, Soyano Takashi, Machida Chiyoko, Machida Yasunori
College of Bioscience and Biotechnology, Chubu University and CREST, Japan Science and Technology Corporation, 1200 Matsumoto-cho, Kasugai, Aichi 487-8501, Japan.
Genes Cells. 2004 Dec;9(12):1199-211. doi: 10.1111/j.1365-2443.2004.00798.x.
Cytokinesis is the critical step during which daughter cells are separated. We showed previously that a protein complex that consists of NACK1 (and NACK2) kinesin-like protein and NPK1 MAPKKK and its substrate NQK1 MAPKK are required for progression of cytokinesis in Nicotiana tabacum. The genome of Arabidopsis thaliana encodes homologues of NACK1 and NACK2, namely, AtNACK1/HINKEL and STUD/TETRASPORE/AtNACK2, respectively. Loss-of-function mutations in AtNACK1/HINKEL and STUD/TETRASPORE/AtNACK2 result in the occasional failure of somatic and male-meiotic cytokinesis, respectively. However, it is likely that these genes function redundantly to some extent in somatic tissues and female gametogenesis. We describe the phenotypes of Arabidopsis plants that have mutations in both the AtNACK1/HINKEL and STUD/TETRASPORE/AtNACK2 genes. These phenotypes suggest that the two genes are essential during both male and female gametogenesis. Female gametes with atnack1 atnack2 double mutations failed to cellularize and to generate a central cell, synergids and the egg cells. Male gametes with atnack1 atnack2 mutations were also not transmitted to the next generation. The AtNACK1/HINKEL and STUD/TETRASPORE/AtNACK2 genes for kinesin-like proteins have overlapping functions that are essential for gametogenetic cytokinesis. They appear to be essential components of a MAP kinase cascade that promotes cytokinesis of plant cells in both gametophytic (haploid) and sporophytic (diploid) proliferation.
胞质分裂是子细胞分离的关键步骤。我们之前表明，由NACK1（和NACK2）类驱动蛋白以及NPK1 MAPKKK及其底物NQK1 MAPKK组成的蛋白复合物是烟草胞质分裂进程所必需的。拟南芥基因组分别编码NACK1和NACK2的同源物，即AtNACK1/HINKEL和STUD/TETRASPORE/AtNACK2。AtNACK1/HINKEL和STUD/TETRASPORE/AtNACK2功能缺失突变分别导致体细胞和雄配子减数分裂胞质分裂偶尔失败。然而，这些基因可能在体细胞组织和雌配子发生中在一定程度上功能冗余。我们描述了AtNACK1/HINKEL和STUD/TETRASPORE/AtNACK2基因均发生突变的拟南芥植株的表型。这些表型表明这两个基因在雄配子和雌配子发生过程中都是必需的。具有atnack1 atnack2双突变的雌配子无法进行细胞化，也无法产生中央细胞、助细胞和卵细胞。具有atnack1 atnack2突变的雄配子也无法传递给下一代。类驱动蛋白的AtNACK1/HINKEL和STUD/TETRASPORE/AtNACK2基因具有重叠功能，这些功能对于配子发生的胞质分裂至关重要。它们似乎是促分裂原活化蛋白激酶级联反应的重要组成部分，该级联反应在配子体（单倍体）和孢子体（二倍体）增殖过程中促进植物细胞的胞质分裂。
