CHASE domain-containing receptors play an essential role in the cytokinin response of the moss Physcomitrella patens.
CHASE domain-containing receptors play an essential role in the cytokinin response of the moss Physcomitrella patens.
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含Chase结构域的受体在苔藓Physcomitrella patens的细胞分裂素反应中起着至关重要的作用。
DOI：
10.1093/jxb/erv479
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发表时间：
2016-02
影响因子：
6.9
通讯作者：
Heyl A
中科院分区：
文献类型：
--
作者：
von Schwartzenberg K;Lindner AC;Gruhn N;Šimura J;Novák O;Strnad M;Gonneau M;Nogué F;Heyl A
三个经典的CHASE结构域的小立碗藓受体的功能表征揭示了其在苔藓细胞分裂素反应中的关键作用。虽然细胞分裂素作用的分子基础在显花植物中已被很好地理解，但关于细胞分裂素在早期分化的陆地植物中的信号转导却知之甚少。本文报道了小立碗藓（Physcomitrella patens（Hedw.）B.S.编码三种经典的细胞分裂素受体，即含有CHASE结构域的组氨酸激酶CHK 1、CHK 2和CHK 3。在与受体缺陷型拟南芥原生质体的互补试验以及细胞分裂素结合试验中，我们发现CHK 1和CHK 2受体可以在细胞分裂素感知中起作用的证据。使用基因靶向，我们产生了一系列CHK敲除突变体，包括单（Δ chk 1，Δ chk 2，Δ chk 3），双（Δ chk 1，2，Δ chk 1，3，Δ chk 2，3）和三（Δ chk 1，2，3）突变体。突变体的特征在于它们的细胞分裂素反应和分化能力。虽然野生型不能在高剂量的细胞分裂素（1 μM苄基腺嘌呤）下生长，但Δ chk 1，2，3突变体显示出正常的原丝体生长。芽诱导试验表明，所有三个细胞分裂素受体有助于触发出芽，虽然在不同程度上。此外，虽然三重突变体在该生物测定中没有显示出响应，但剩余的突变体以不同的方式对不同类型和浓度的细胞分裂素显示出出芽响应。突变体中细胞分裂素水平的测定显示任何细胞分裂素都没有剧烈的变化;因此，与拟南芥相反，揭示了细胞分裂素信号对稳态的影响很小。总之，我们的研究提供了第一次深入了解细胞分裂素的分子作用在早期分歧的土地植物，并表明，CHK受体在芽诱导和配子体发育中起着至关重要的作用。
Functional characterization of the three classical CHASE domain-containing receptors from Physcomitrella patens reveals their key role in the moss cytokinin response. While the molecular basis for cytokinin action is quite well understood in flowering plants, little is known about the cytokinin signal transduction in early diverging land plants. The genome of the bryophyte Physcomitrella patens (Hedw.) B.S. encodes three classical cytokinin receptors, the CHASE domain-containing histidine kinases, CHK1, CHK2, and CHK3. In a complementation assay with protoplasts of receptor-deficient Arabidopsis thaliana as well as in cytokinin binding assays, we found evidence that CHK1 and CHK2 receptors can function in cytokinin perception. Using gene targeting, we generated a collection of CHK knockout mutants comprising single (Δchk1, Δchk2, Δchk3), double (Δchk1,2, Δchk1,3, Δchk2,3), and triple (Δchk1,2,3) mutants. Mutants were characterized for their cytokinin response and differentiation capacities. While the wild type did not grow on high doses of cytokinin (1 µM benzyladenine), the Δchk1,2,3 mutant exhibited normal protonema growth. Bud induction assays showed that all three cytokinin receptors contribute to the triggering of budding, albeit to different extents. Furthermore, while the triple mutant showed no response in this bioassay, the remaining mutants displayed budding responses in a diverse manner to different types and concentrations of cytokinins. Determination of cytokinin levels in mutants showed no drastic changes for any of the cytokinins; thus, in contrast to Arabidopsis, revealing only small impacts of cytokinin signaling on homeostasis. In summary, our study provides a first insight into the molecular action of cytokinin in an early diverging land plant and demonstrates that CHK receptors play an essential role in bud induction and gametophore development.