School of Life Sciences, Jawaharlal Nehru University, New Delhi 110 067, India.
Plant Cell Physiol. 2010 Oct;51(10):1788-99. doi: 10.1093/pcp/pcq139. Epub 2010 Sep 7.
Perception of red light (400 μmol photon m²/s) by the shoot bottom turned off the greening process in wheat. To understand the signaling cascade leading to this photomorphogenic response, certain signaling components were probed in seedlings grown in different light regimes. Upon analysis the gene expression of heterotrimeric Gα and Gβ were severely down-regulated in seedlings grown without vermiculite and having their shoot bottom exposed to red light (R/V-) and was similar to that of dark-grown seedlings. Supplementing the red-light-grown V- seedlings with blue light resulted in up-regulation of both Gα and Gβ expression, suggesting that blue light is able to modulate G protein expression. Treatment of cytokinin analog benzyladenine to cytokinin-deficient red-light-grown R/V- seedlings resulted in up-regulation of gene expression of both Gα and Gβ. To probe further, modulators of signal transduction pathway--AlF₃ (G protein activator), LaCl₃ (Ca(2+) channel blocker), NaF (nonspecific phosphatase inhibitor), or calmodulin (CaM) antagonists trifluoperazine (TFP) and N-(6-aminohexyl)-5-chloro-1-nafthalene-sulfonamide (W-7)--were added along with Hoagland solution to the roots of 4-day-old etiolated seedlings, grown on germination paper and transferred to red light. AlF₃, LaCl₃, NaF failed to elicit any photomorphogenic response. However, CaM antagonists TFP and W-7 significantly reversed the red-light-induced suppression of photomorphogenesis. Phosphorylation of proteins assayed in the absence or presence of CaM antagonist TFP revealed respective up-regulation or down-regulation of phosphorylation of several plastidic proteins in R/V- seedlings. These suggest that signal transduction of red light perceived by the shoot bottom to suppress photomorphogenesis is mediated by CaM-dependent protein kinases.
红光（400 μmol 光子 m²/s）照射到小麦芽的底部会阻止其变绿。为了了解导致这种光形态建成反应的信号级联，研究了在不同光照条件下生长的幼苗中的某些信号成分。分析表明，在没有蛭石且芽底部暴露在红光（R/V-）下生长的幼苗中，异三聚体 Gα 和 Gβ 的基因表达严重下调，与黑暗生长的幼苗相似。用蓝光补充在红光下生长的 V-幼苗，导致 Gα 和 Gβ 的表达上调，表明蓝光能够调节 G 蛋白的表达。用细胞分裂素类似物苄腺嘌呤处理细胞分裂素缺乏的红光下生长的 R/V-幼苗，导致 Gα 和 Gβ 的基因表达上调。为了进一步探究，添加了信号转导途径调节剂——AlF₃（G 蛋白激活剂）、LaCl₃（Ca²⁺通道阻滞剂）、NaF（非特异性磷酸酶抑制剂）或钙调蛋白（CaM）拮抗剂三氟拉嗪（TFP）和 N-（6-氨基己基）-5-氯-1-萘磺酰胺（W-7）——连同 Hoagland 溶液一起添加到在发芽纸上生长并转移到红光下的 4 天大的黄化幼苗的根部。AlF₃、LaCl₃、NaF 未能引起任何光形态建成反应。然而，CaM 拮抗剂 TFP 和 W-7 显著逆转了红光诱导的光形态建成抑制。在不存在或存在 CaM 拮抗剂 TFP 的情况下测定蛋白质的磷酸化，发现 R/V- 幼苗中几种质体蛋白的磷酸化分别上调或下调。这些表明，由芽底部感知的红光信号转导抑制光形态建成是由 CaM 依赖性蛋白激酶介导的。
