在ipt-GUS转基因拟南芥中双组分信号传导基因应答体内细胞分裂素的增加

ipt—GUS转录融合基因在拟南芥植物中表达，其体内细胞分裂素的含量可达到野生型的20-30倍。从拟南芥种子萌发后的6、12、20和30d四个时间分析了植物体内细胞分裂素含量的提高对其双组分信号传导系统中基因的影响。研究发现：细胞分裂素受体基因CRE1比CKI1基因更容易被增加的植物细胞分裂素诱导表达。拟南芥植物细胞分裂素反应调节基因ARR4和ARR5在植物发育的不同时期应答植物体内增加的植物细胞分裂素，ARR4的应答反应比ARR5早，种子萌发后的第6天幼苗真叶形成初期，ARR4基因被明显涛导；而ARR5的应答反应在幼苗真叶形成后的几个时间段均能检测到，并且在种子萌发后的第20天，花枝形成开始时特别明显。在双组分信号传导途径中，从受体到反应调节基因传导磷酸基团的传导基因AHP4在幼苗发育的后期种子萌发后的第20和30天，应答植物体内增加的植物细胞分裂素，并且在花枝形成初期比较明显。

Activation of Genes Presumed in Cytokinin Signal Pathway of Two-component System in Response to the Increased Cytokinin Contents in ipt-GUS Transgenic Arabidopsis

The ipt-GUS activated transgenic Arabidopsis had 20-25 fold higher cytokinin contents than the wild type. Changes in cytokinin content in vivo triggering gene expressions involved in signal pathway of two-component system have been analyzed on the day of 6 d, 12 d, 20 d and 30 d after seed cultivation on MS medium in light conditions. The results showed that the two cytokinin receptors, His-kinase CRE1 was more sensitive to the increased cytokinin contents than CKI1. Arabidopsis response regulators, ARR4 and ARR5, were induced by the increased cytokinin contents at different time after seed germination. ARR4 responded to cytokinins at early time of seed germination, especially on the 6 d when seedlings were around true leaf initiation, while cytokinins induced ARR5 activation after 6 d of seed cultivation in light conditions, an obvious increase was on the 20 d when seedlings were around inflorescent shoot initiation. Hpt-type transmitter kinase AHP4 increased its activation by cytokinin induction only between the 20 d and 30 d after seed cultivation in light conditions, and an obvious increase was on the 20 d.