Higuchi Masayuki, Pischke Melissa S, Mähönen Ari Pekka, Miyawaki Kaori, Hashimoto Yukari, Seki Motoaki, Kobayashi Masatomo, Shinozaki Kazuo, Kato Tomohiko, Tabata Satoshi, Helariutta Ykä, Sussman Michael R, Kakimoto Tatsuo
Department of Biology, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan.
Proc Natl Acad Sci U S A. 2004 Jun 8;101(23):8821-6. doi: 10.1073/pnas.0402887101. Epub 2004 May 27.
Since their discovery as cell-division factors in plant tissue culture about five decades ago, cytokinins have been hypothesized to play a central role in the regulation of cell division and differentiation in plants. To test this hypothesis in planta, we isolated Arabidopsis plants lacking one, two, or three of the genes encoding a subfamily of histidine kinases (CRE1, AHK2, and AHK3) that function as cytokinin receptors. Seeds were obtained for homozygous plants containing mutations in all seven genotypes, namely single, double, and triple mutants, and the responses of germinated seedlings in various cytokinin assays were compared. Both redundant and specific functions for the three different cytokinin receptors were observed. Plants carrying mutations in all three genes did not show cytokinin responses, including inhibition of root elongation, inhibition of root formation, cell proliferation in and greening of calli, and induction of cytokinin primary-response genes. The triple mutants were small and infertile, with a reduction in meristem size and activity, yet they possessed basic organs: roots, stems, and leaves. These results confirm that cytokinins are a pivotal class of plant growth regulators but provide no evidence that cytokinins are required for the processes of gametogenesis and embryogenesis.
大约五十年前，细胞分裂素作为植物组织培养中的细胞分裂因子被发现以来，人们一直推测其在植物细胞分裂和分化的调控中发挥核心作用。为了在植物体内验证这一假设，我们分离出了拟南芥植株，这些植株缺失了编码作为细胞分裂素受体的组氨酸激酶亚家族（CRE1、AHK2和AHK3）的一个、两个或三个基因。获得了所有七种基因型（即单突变体、双突变体和三突变体）均含有突变的纯合植株的种子，并比较了萌发幼苗在各种细胞分裂素测定中的反应。观察到三种不同细胞分裂素受体具有冗余和特定功能。携带所有三个基因突变的植株未表现出细胞分裂素反应，包括根伸长抑制、根形成抑制、愈伤组织细胞增殖和绿化以及细胞分裂素初级反应基因的诱导。三突变体植株矮小且不育，分生组织大小和活性降低，但仍具有根、茎和叶等基本器官。这些结果证实细胞分裂素是一类关键的植物生长调节剂，但没有证据表明细胞分裂素是配子发生和胚胎发生过程所必需的。
