The RCN1-encoded A subunit of protein phosphatase 2A increases phosphatase activity in vivo
The RCN1-encoded A subunit of protein phosphatase 2A increases phosphatase activity in vivo
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DOI：
10.1046/j.1365-313x.1999.00607.x
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发表时间：
1999-11-01
期刊：
影响因子：
7.2
通讯作者：
DeLong, A
中科院分区：
文献类型：
--
作者：
Deruère, J;Jackson, K;DeLong, A
蛋白磷酸酶2A(PP2A)是一种异源三聚体丝氨酸/苏氨酸专一性蛋白磷酸酶，由一个催化C亚基和两个不同的调节亚基A和B组成。T-DNA插入突变会损害根部卷曲、幼苗器官伸长和顶端下胚轴挂钩的形成。我们已经使用体内和体外试验来评估rcn1突变对幼苗中PP2A活性的影响。在rcn1突变体幼苗的提取物中，PP2A活性降低，这种降低不是由于催化亚基表达的减少。在器官伸长试验中，突变幼苗的根对磷酸酶抑制剂冈田酸和斑泻素表现出更高的敏感性。深色生长的幼苗，而不是浅色生长的幼苗，也表现出对抑制剂的敏感性增加。此外，斑泻素对野生型幼苗的处理模拟了rcn1在卷根、挥根和下胚轴挂钩形成试验中的缺陷。在野生型幼苗的根中，RCN1基因在根尖高水平表达，在中柱花序和侧根原基中表达较低。在新梢中，RCN1在黄化的下胚轴的顶端钩和基本的、快速伸长的细胞中表达，在轻度生长的幼苗的新梢分生组织和叶原基中表达。我们的结果表明，野生型RCN1编码的A亚基作为PP2A全酶的正调控因子，增加了对参与器官伸长和差异细胞伸长反应(如卷根)的底物的活性。
Protein phosphatase 2A (PP2A), a heterotrimeric serine/threonine-specific protein phosphatase, comprises a catalytic C subunit and two distinct regulatory subunits, A and B. The RCN1 gene encodes one of three A regulatory subunits in Arabidopsis thaliana. A T-DNA insertion mutation at this locus impairs root curling, seedling organ elongation and apical hypocotyl hook formation. We have used in vivo and in vitro assays to gauge the impact of the rcn1 mutation on PP2A activity in seedlings. PP2A activity is decreased in extracts from rcn1 mutant seedlings, and this decrease is not due to a reduction in catalytic subunit expression. Roots of mutant seedlings exhibit increased sensitivity to the phosphatase inhibitors okadaic acid and cantharidin in organ elongation assays. Shoots of dark-grown, but not light-grown seedlings also show increased inhibitor sensitivity. Furthermore, cantharidin treatment of wild-type seedlings mimics the rcn1 defect in root curling, root waving and hypocotyl hook formation assays. In roots of wild-type seedlings, RCN1 mRNA is expressed at high levels in root tips, and accumulates to lower levels in the pericycle and lateral root primordia. In shoots, RCN1 is expressed in the apical hook and the basal, rapidly elongating cells in etiolated hypocotyls, and in the shoot meristem and leaf primordia of light-grown seedlings. Our results show that the wild-type RCN1-encoded A subunit functions as a positive regulator of the PP2A holoenzyme, increasing activity towards substrates involved in organ elongation and differential cell elongation responses such as root curling.