The Arabidopsis Mitogen-Activated Protein Kinase Phosphatase PP2C5 Affects Seed Germination, Stomatal Aperture, and Abscisic Acid-Inducible Gene Expression
The Arabidopsis Mitogen-Activated Protein Kinase Phosphatase PP2C5 Affects Seed Germination, Stomatal Aperture, and Abscisic Acid-Inducible Gene Expression
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DOI：
10.1104/pp.110.156109
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发表时间：
2010-07-01
期刊：
影响因子：
7.4
通讯作者：
Gust, Andrea A.
中科院分区：
文献类型：
--
作者：
Brock, Anita K.;Willmann, Roland;Gust, Andrea A.
脱落酸 (ABA) 是一种重要的植物激素，调节植物中的各种细胞过程，包括气孔开放和种子萌发。尽管通过丝裂原激活蛋白激酶 (MAPK) 进行的蛋白质磷酸化被认为在 ABA 信号传导中很重要，但相应的磷酸酶在很大程度上是未知的。在这里，我们发现拟南芥 (Arabidopsis thaliana) 中蛋白磷酸酶 2C (PP2C) 家族的成员 PP2C5 充当 MAPK 磷酸酶。 PP2C5 蛋白主要在细胞核中与应激诱导的 MPK3、MPK4 和 MPK6 共定位并直接相互作用。重要的是，PP2C5 水平的改变会影响 MAPK 的激活。 PP2C5 耗尽的拟南芥植物表现出 ABA 诱导的 MPK3 和 MPK6 激活增强，而烟草 (Nicotiana Benthamiana) 中 PP2C5 的异位表达则产生相反的效果，水杨酸诱导的蛋白激酶和伤口诱导的蛋白激酶这两种 MAPK 在 ABA 处理后不再被激活。此外，PP2C5 的基因表达本身受到 ABA 处理的影响，PP2C5 的耗竭会导致 ABA 反应的改变。 PP2C5 或 AP2C1（PP2C5 的密切同源物）中的功能缺失突变导致正常生长条件下气孔孔径增加，并导致种子萌发中部分 ABA 不敏感表型，这在 pp2c5 ap2c1 双突变体系中最为突出。此外，突变体植物中 ABA 诱导基因（如 ABI1、ABI2、RD29A 和 Erd10）的反应降低。因此，我们认为 PP2C5 作为 MAPK 磷酸酶，积极调节种子发芽、气孔关闭和 ABA 诱导的基因表达。
Abscisic acid (ABA) is an important phytohormone regulating various cellular processes in plants, including stomatal opening and seed germination. Although protein phosphorylation via mitogen-activated protein kinases (MAPKs) has been suggested to be important in ABA signaling, the corresponding phosphatases are largely unknown. Here, we show that a member of the Protein Phosphatase 2C (PP2C) family in Arabidopsis (Arabidopsis thaliana), PP2C5, is acting as a MAPK phosphatase. The PP2C5 protein colocalizes and directly interacts with stress-induced MPK3, MPK4, and MPK6, predominantly in the nucleus. Importantly, altered PP2C5 levels affect MAPK activation. Whereas Arabidopsis plants depleted of PP2C5 show an enhanced ABA-induced activation of MPK3 and MPK6, ectopic expression of PP2C5 in tobacco (Nicotiana benthamiana) resulted in the opposite effect, with the two MAPKs salicylic acid-induced protein kinase and wound-induced protein kinase not being activated any longer after ABA treatment. Moreover, depletion of PP2C5, whose gene expression itself is affected by ABA treatment, resulted in altered ABA responses. Loss-of-function mutation in PP2C5 or AP2C1, a close PP2C5 homolog, resulted in an increased stomatal aperture under normal growth conditions and a partial ABA-insensitive phenotype in seed germination that was most prominent in the pp2c5 ap2c1 double mutant line. In addition, the response of ABA-inducible genes such as ABI1, ABI2, RD29A, and Erd10 was reduced in the mutant plants. Thus, we suggest that PP2C5 acts as a MAPK phosphatase that positively regulates seed germination, stomatal closure, and ABA-inducible gene expression.