Key Laboratory of Plant Molecular Physiology, CAS Center for Excellence in Molecular Plant Sciences, Institute of Botany, Chinese Academy of Sciences, Beijing, China.
University of Chinese Academy of Sciences, Beijing, China.
J Exp Bot. 2018 Jun 27;69(15):3587-3599. doi: 10.1093/jxb/ery158.
In rice, and other major cereal grass crops, stomata are arranged in linear files parallel to the long growth axis of leaves. Each stomatal unit comprises two dumbbell-shaped guard cells flanked by two subsidiary cells. These morphological and developmental characteristics enable grass stomata to respond to environmental changes more efficiently. Cyclin-dependent kinases (CDKs) and their cyclin partners co-ordinate cell proliferation and differentiation during the development of multicellular organisms. In contrast to animals, plants have many more types and members of cyclins. In Arabidopsis, four A2-type cyclins (CYCA2s) function redundantly in regulating CDKB1 activity to promote the asymmetric division for stomatal initiation and the symmetric division of guard mother cells (GMCs). In this study, we examine the function of the single A2-type cyclin in rice, OsCYCA2;1, as well the single B1-type CDK, OsCDKB1;1. Cross-species complementation tests demonstrated that OsCYCA2;1 and OsCDKB1;1 could complement the defective stomatal phenotypes of Arabidopsis cyca2 and cdkb1 mutants, but also could suppress DNA endoduplication and cell enlargement. The early asymmetric divisions that establish the stomatal lineages are often missing within the stomatal cell files of OsCYCA2;1-RNAi rice transgenic lines, leading to a significantly reduced stomatal production. However, GMC divisions are not disrupted either in OsCYCA2;1-RNAi or in OsCDKB1;1-RNAi rice transgenic lines as expected. Our results demonstrate a conserved but diverged function and behavior of rice A2-type cyclins, which might be associated with the distinct stomatal development pathways between rice and Arabidopsis.
在水稻和其他主要的谷类作物中，气孔呈线性排列，与叶片的长生长轴平行。每个气孔单位由两个哑铃形的保卫细胞组成，两侧是两个附属细胞。这些形态和发育特征使禾本科植物的气孔能够更有效地响应环境变化。细胞周期蛋白依赖性激酶（CDKs）及其细胞周期蛋白伴侣在多细胞生物的发育过程中协调细胞增殖和分化。与动物不同，植物的细胞周期蛋白种类和成员要多得多。在拟南芥中，四种 A2 型细胞周期蛋白（CYCA2s）通过冗余作用调节 CDKB1 的活性，以促进气孔起始的不对称分裂和保卫母细胞（GMCs）的对称分裂。在这项研究中，我们研究了水稻 A2 型细胞周期蛋白 OsCYCA2;1 的功能，以及单个 B1 型细胞周期蛋白激酶 OsCDKB1;1。种间互补测试表明，OsCYCA2;1 和 OsCDKB1;1 可以互补拟南芥 cyca2 和 cdkb1 突变体缺陷型气孔表型，但也可以抑制 DNA 内复制和细胞增大。建立气孔谱系的早期不对称分裂通常在 OsCYCA2;1-RNAi 水稻转基因系的气孔细胞系中缺失，导致气孔产生显著减少。然而，正如预期的那样，在 OsCYCA2;1-RNAi 或 OsCDKB1;1-RNAi 水稻转基因系中，GMC 分裂并没有被破坏。我们的研究结果表明，水稻 A2 型细胞周期蛋白具有保守但分化的功能和行为，这可能与水稻和拟南芥之间不同的气孔发育途径有关。
