Abscisic acid (ABA) plays an important role in plant growth and developmental processes. Although some ABA signal molecules, such as cADPR, Ca2+, etc., have been reported, therewas no evidence proving the involvement of cAMP in ABA signal transduction. In this present study, the constructed gene (rd29A GUS ) was transformed into Nicotiana tabacum, and calli was induced from the transgenic plant. The suspension cells obtained from the callus grew well and uniformly. Treatment of the suspension cells with ABA led to an increase in GUS activity, indicating that these transgenic suspension cells are useful for the study of ABA signaling. Addition of nicotinamide (cADPR inhibitor) or U73122(phospholiphase C inhibitor) could only partially inhibit the increase of GUS activity elicited by ABA. The inhibitory effect of nicotinamide was enhanced by application of K252a (inhibitor of protein kinase). Treatment of the suspension cells with 8-Br-cAMP, a membrane permeable analogue of cAMP, could partially replace the effect of ABA. Furthermore, intracellular addition of IBMX (phosphodiesterase inhibitor) mimicked the effect of exogenous cAMP on the deduction of expression of rd29A promoter. These results suggested that cAMP was an important messenger in ABA signal transduction in tobacco suspension cell.
cAMP参与烟草悬浮细胞的ABA信号转导
刘 璞 孟令军 张会霞 陈 珈* 王学臣
（中国农业大学生物学院，植物生理生化国家重点开放实验室，北京100094）
摘要： ABA诱导型启动子( rd29A)重组到报告基因(GUS)的上游构建表达载体.通过农杆菌介导转化烟草,获得转基因植株.将转基因植株诱导愈伤组织,建立稳定、均一的转rd29A-GUS融合基因的悬浮培养细胞系.用ABA处理悬浮细胞24 h后GUS活性显著升高,说明外源ABA能够诱导rd29A启动子的表达,获得了用于ABA信号转导研究的实用细胞系.在ABA激活表达的细胞介质中加入尼克酰胺(cADPR合成酶的抑制剂)或U73122(PLC抑制剂)只能部分抑制ABA的效应,但如果加入蛋白激酶抑制剂K252a,抑制效果达95%以上.用可跨膜的cAMP的类似物8-Br-cAMP处理细胞发现,它能代替ABA的作用;当介质中加入1 mmol/L IBMX(磷酸二酯酶的抑制剂)增加cAMP的稳定性,发现低浓度的8-Br-cAMP与ABA相同的效应.以上结果表明cAMP参与了烟草悬浮细胞中ABA信号的传递.
关键词： 烟草；脱落酸；环腺苷一磷酸；B-葡糖醛酸酶；报告基因；信号转导
通讯作者。E-mail:chenja@public.bta.net.cn.
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