Dominant and recessive mutations in the Raf-like kinase HT1 gene completely disrupt stomatal responses to CO2 in Arabidopsis.
Dominant and recessive mutations in the Raf-like kinase HT1 gene completely disrupt stomatal responses to CO2 in Arabidopsis.
复制标题
RAF样激酶HT1基因中的显性和隐性突变完全破坏了拟南芥中对CO2的气孔反应。
DOI：
10.1093/jxb/erw134
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发表时间：
2016-05
影响因子：
6.9
通讯作者：
Iba K
中科院分区：
文献类型：
--
作者：
Hashimoto-Sugimoto M;Negi J;Monda K;Higaki T;Isogai Y;Nakano T;Hasezawa S;Iba K
功能丧失和功能获得的ht 1拟南芥突变体已完全破坏CO2的反应，由于减少和增强激酶活性，分别。HT 1（HIGH LEAF TEMPERATURE 1）是通过正向遗传筛选分离出的第一个与CO2胁迫下气孔开度变化相关的基因。HT 1基因编码主要在保卫细胞中表达的蛋白激酶。拟南芥中功能丧失的ht 1 -1和ht 1 -2突变体具有CO2超敏感性气孔关闭，伴随着它们的激酶活性在体外降低。除了这些突变体外，本研究还分离或获得了5个新的ht 1等位基因（ht 1 -3，ht 1 -4，ht 1 -5，ht 1 -6和ht 1 -7）。在这些突变体中，只有ht 1 -3具有显性突变体表型，并且由于CO2不敏感而具有广泛开放的气孔。ht 1 -3突变体具有影响非保守残基（R102 K）的错义突变，而其他六个隐性突变体在激酶活性所需的催化结构域中的高度保守残基中具有突变。我们发现显性突变不影响HT 1的表达或磷酸化酪蛋白（一种通用激酶底物）的能力，但它确实影响体外自磷酸化活性。HT 1的3D结构模型还显示R102残基从激酶表面突出，这意味着形成寡聚体和/或与其靶标相互作用的作用。我们表明，功能丧失和功能获得的ht 1突变体完全破坏CO2的反应，虽然他们有正常的响应阿坝。此外，光诱导的气孔开放度在ht 1 -3中较小，在ht 1 -2中更小。综上所述，这些结果表明，HT 1是一个关键的调节CO2信号，并部分参与光诱导的气孔开放途径。
Loss-of-function and gain-of-function ht1 Arabidopsis mutants have completely disrupted CO2 responses due to reduced and enhanced kinase activities, respectively. HT1 (HIGH LEAF TEMPERATURE 1) is the first component associated with changes in stomatal aperture in response to CO2 to be isolated by forward genetic screening. The HT1 gene encodes a protein kinase expressed mainly in guard cells. The loss-of-function ht1-1 and ht1-2 mutants in Arabidopsis thaliana have CO2-hypersensitive stomatal closure with concomitant reductions in their kinase activities in vitro. In addition to these mutants, in this study we isolate or obtaine five new ht1 alleles (ht1-3, ht1-4, ht1-5, ht1-6, and ht1-7). Among the mutants, only ht1-3 has a dominant mutant phenotype and has widely opened stomata due to CO2 insensitivity. The ht1-3 mutant has a missense mutation affecting a non-conserved residue (R102K), whereas the other six recessive mutants have mutations in highly conserved residues in the catalytic domains required for kinase activity. We found that the dominant mutation does not affect the expression of HT1 or the ability to phosphorylate casein, a universal kinase substrate, but it does affect autophosphorylation activity in vitro. A 3D structural model of HT1 also shows that the R102 residue protrudes from the surface of the kinase, implying a role for the formation of oligomers and/or interaction with its targets. We demonstrate that both the loss-of-function and gain-of-function ht1 mutants have completely disrupted CO2 responses, although they have normal responses to ABA. Furthermore, light-induced stomatal opening is smaller in ht1-3 and much smaller in ht1-2. Taken together, these results indicate that HT1 is a critical regulator for CO2 signaling and is partially involved in the light-induced stomatal opening pathway.