Department of Botany, University of California, Berkeley, California 94720.
Plant Physiol. 1985 May;78(1):192-8. doi: 10.1104/pp.78.1.192.
Pulse-labeling of barley (Hordeum vulgare L. cv Himalaya) aleurone layers incubated for 13 hours in 2.5 micromolar gibberellic acid (GA(3)) with or without 5 millimolar CaCl(2) shows that alpha-amylase isozymes 3 and 4 are not synthesized in vivo in the absence of Ca(2+). A cDNA clone for alpha-amylase was isolated and used to measure alpha-amylase mRNA levels in aleurone layers incubated in the presence and absence of Ca(2+). No difference was observed in alpha-amylase mRNA levels between layers incubated for 12 hours in 2.5 micromolar GA(3) with 5 millimolar CaCl(2) and layers incubated in GA(3) alone. RNA isolated from layers incubated for 12 hours in GA(3) with and without Ca(2+) was translated in vitro and was found to produce the same complement of translation products regardless of the presence of Ca(2+) in the incubation medium. Immunoprecipitation of translation products showed that the RNA for alpha-amylase synthesized in Ca(2+)-deprived aleurone layers was translatable. Ca(2+) is required for the synthesis of alpha-amylase isozymes 3 and 4 at a step after mRNA accumulation and processing.
用 2.5 微摩尔赤霉素（GA(3)）处理大麦糊粉层 13 小时，在有或没有 5 毫摩尔氯化钙（CaCl(2)）的条件下进行脉冲标记，结果表明，在没有 Ca(2+)的情况下，α-淀粉酶同工酶 3 和 4 不能在体内合成。分离到一个α-淀粉酶的 cDNA 克隆，并用于测量在有和没有 Ca(2+)存在的情况下糊粉层中α-淀粉酶 mRNA 水平。在 2.5 微摩尔 GA(3)中培养 12 小时的糊粉层与单独培养 GA(3)的糊粉层之间，α-淀粉酶 mRNA 水平没有差异。用 GA(3)培养 12 小时，有和没有 Ca(2+)的糊粉层中分离出的 RNA 在体外翻译，并发现无论在孵育介质中是否存在 Ca(2+)，都产生相同的翻译产物。免疫沉淀翻译产物表明，在 Ca(2+)剥夺的糊粉层中合成的α-淀粉酶 RNA 是可转译的。Ca(2+)是α-淀粉酶同工酶 3 和 4 在 mRNA 积累和加工后的合成所必需的。
