Ito T, Takahashi N, Shimura Y, Okada K
Department of Botany, Faculty of Science, Kyoto University, Japan.
Plant Cell Physiol. 1997 Mar;38(3):248-58. doi: 10.1093/oxfordjournals.pcp.a029160.
During the course of characterizing fragments bound to an Arabidopsis floral protein AGAMOUS in vivo, a gene encoding a putative serine/threonine protein kinase was found on one of the fragments. The deduced 426 amino acid residues of the gene, named APK2a, are 65% identical to a previously reported Arabidopsis serine/threonine protein kinase, APK1a. The gene is composed of 6 exons and maps at 10 cM from the upper end of chromosome 1. Northern hybridization experiments indicated that the gene is strongly expressed in leaves, moderately in roots, and very weakly in flowers. Further in situ analysis of the expression in floral buds showed that the APK2a gene is expressed at pedicels, is not expressed at the floral organ primordia of wild type floral buds, but is moderately expressed in the floral organ primordia of the agamous mutant. In vitro binding assay suggest that the AGAMOUS protein binds to a sequence similar to, but different from, the known MADS-binding consensus sequences, the CArG box, located 3' downstream of the APK2a gene. These results suggest that APK2a expression is negatively regulated by the AG protein. A close homologue of the APK2a gene, named APK2b, was also isolated from the Arabidopsis cDNA library. The expression pattern of the APK2b gene differs from that of APK2a. It is strongly expressed in leaves, moderately in flowers, and weakly in roots.
在对体内与拟南芥花蛋白AGAMOUS结合的片段进行表征的过程中，在其中一个片段上发现了一个编码假定丝氨酸/苏氨酸蛋白激酶的基因。该基因推导的426个氨基酸残基被命名为APK2a，与先前报道的拟南芥丝氨酸/苏氨酸蛋白激酶APK1a有65%的同一性。该基因由6个外显子组成，位于第1号染色体上端10厘摩处。Northern杂交实验表明，该基因在叶中强烈表达，在根中适度表达，在花中非常弱地表达。对花芽表达的进一步原位分析表明，APK2a基因在花梗处表达，在野生型花芽的花器官原基中不表达，但在无配子突变体的花器官原基中适度表达。体外结合试验表明，AGAMOUS蛋白与APK2a基因3'下游一个与已知MADS结合共有序列CArG框相似但不同的序列结合。这些结果表明，APK2a的表达受AG蛋白的负调控。还从拟南芥cDNA文库中分离出APK2a基因的一个紧密同源物，命名为APK2b。APK2b基因的表达模式与APK2a不同。它在叶中强烈表达，在花中适度表达，在根中弱表达。
