Lack of ACTPK1, an STY kinase, enhances ammonium uptake and use, and promotes growth of rice seedlings under sufficient external ammonium
Lack of ACTPK1, an STY kinase, enhances ammonium uptake and use, and promotes growth of rice seedlings under sufficient external ammonium
复制标题
DOI：
10.1111/tpj.13824
复制
发表时间：
2018-03-01
期刊：
影响因子：
7.2
通讯作者：
Hayakawa, Toshihiko
中科院分区：
文献类型：
--
作者：
Beier, Marcel P.;Obara, Mitsuhiro;Hayakawa, Toshihiko
通过高亲和力转运系统（HATS）进入植物根系的铵流入量在升高的外部铵下被下调，从而防止铵毒性。在铵喂养的拟南芥中，负责HATS活性的铵转运蛋白1（AMT1）三聚体通过钙调磷酸酶B样蛋白1-钙调磷酸酶B样蛋白相互作用蛋白激酶23复合物和其他尚未鉴定的蛋白激酶在羧基尾处的保守苏氨酸的磷酸化以剂量依赖性方式变构失活。利用转录组和反向遗传学在铵偏好型水稻，我们揭示了丝氨酸/苏氨酸/酪氨酸蛋白激酶基因OsACTPK1的作用，在下调HATS充足的铵。在野生型根中，ACTPK1 mRNA和蛋白质积累剂量依赖性下充足的铵。为了确定ACTPK1的功能，通过反转录转座子Tos17插入产生了两个缺失ACTPK1的独立突变体。与缺乏插入的分离体相比，这两个突变体在1mm铵下表现出降低的根生长和增加的芽生长，这是由于通过异常高的HATS活性和使用增强了铵的获得。此外，OsACTPK1 cDNA融合到合成的绿色荧光蛋白在其自身的启动子下的引入补充了生长和HATS内流，并建议质膜定位。OsACTPK 1在根细胞中的表达也与铵诱导的OsAMT1; 1和OsAMT1; 2的表达重叠。同时，苏氨酸磷酸化的AMT1水平大幅下降ACTPK1缺陷突变体下生长的充足的铵根。双分子荧光互补实验进一步证实了ACTPK1与AMT1; 2在细胞质膜上的相互作用。总的来说，这些研究结果表明，ACTPK1直接磷酸化和钝化AMT1; 2在水稻幼苗根充足的铵。
Ammonium influx into plant roots via the high-affinity transport system (HATS) is down-modulated under elevated external ammonium, preventing ammonium toxicity. In ammonium-fed Arabidopsis, ammonium transporter 1 (AMT1) trimers responsible for HATS activity are allosterically inactivated in a dose-dependent manner via phosphorylation of the conserved threonine at the carboxyl-tail by the calcineurin B-like protein 1-calcineurin B-like protein-interacting protein kinase 23 complex and other yet unidentified protein kinases. Using transcriptome and reverse genetics in ammonium-preferring rice, we revealed the role of the serine/threonine/tyrosine protein kinase gene OsACTPK1 in down-modulation of HATS under sufficient ammonium. In wild-type roots, ACTPK1 mRNA and protein accumulated dose-dependently under sufficient ammonium. To determine the function of ACTPK1, two independent mutants lacking ACTPK1 were produced by retrotransposon Tos17 insertion. Compared with segregants lacking insertions, the two mutants showed decreased root growth and increased shoot growth under 1mm ammonium due to enhanced ammonium acquisition, via aberrantly high HATS activity, and use. Furthermore, introduction of OsACTPK1 cDNA fused to the synthetic green fluorescence protein under its own promoter complemented growth and the HATS influx, and suggested plasma membrane localization. Root cellular expression of OsACTPK1 also overlapped with that of ammonium-induced OsAMT1;1 and OsAMT1;2. Meanwhile, threonine-phosphorylated AMT1 levels were substantially decreased in roots of ACTPK1-deficient mutants grown under sufficient ammonium. Bimolecular fluorescence complementation assay further confirmed interaction between ACTPK1 and AMT1;2 at the cell plasma membrane. Overall, these findings suggest that ACTPK1 directly phosphorylates and inactivates AMT1;2 in rice seedling roots under sufficient ammonium.