Phytochrome- and gibberellin-mediated regulation of abscisic acid metabolism during germination of photoblastic lettuce seeds
Phytochrome- and gibberellin-mediated regulation of abscisic acid metabolism during germination of photoblastic lettuce seeds
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DOI：
10.1104/pp.107.115162
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发表时间：
2008-03-01
期刊：
影响因子：
7.4
通讯作者：
Toyomasu, Tomonobu
中科院分区：
文献类型：
--
作者：
Sawada, Yoshiaki;Aoki, Miki;Toyomasu, Tomonobu
莴苣（Lactuca sativa）'大急流城'种子的萌发受光敏色素调节。光敏色素的作用包括赤霉素（GA）和脱落酸（阿坝）水平的改变。为了确定光敏色素调节阿坝代谢的分子机制，我们分离了四个编码9-顺式环氧类胡萝卜素双加氧酶（生物合成; LsNCED 1-LsNCED 4）的莴苣cDNA和四个编码阿坝8 '-羟化酶（catenase; LsABA 8 ox 1-LsABA 8 ox 4）的cDNA。阿坝及其催化剂的测定结果表明，红光处理后阿坝水平下降，而阿坝降解产物相酸水平略有上升。定量逆转录-聚合酶链反应分析表明，阿坝水平是由光敏色素通过下调LsNCED 2和LsNCED 4的表达和上调LsABA 8 ox 4的表达来控制的。此外，LsNCED 4的表达水平在GA 1处理后降低，而其他两个基因的表达水平不受影响。在赤霉素生物合成被特异性赤霉素生物合成抑制剂AMO-1618抑制的莴苣种子中，红光也下调了LsNCED 4的表达。这些结果表明光敏色素对阿坝代谢的调节是由GA依赖和非依赖两种机制介导的。空间分析表明，红光处理后，莴苣种子下胚轴侧阿坝下降幅度大于子叶侧。此外，光敏色素调节的阿坝和GA生物合成基因的表达观察下胚轴侧，而不是子叶侧，这表明这种调节发生在光感知网站附近。
Germination of lettuce (Lactuca sativa) 'Grand Rapids' seeds is regulated by phytochrome. The action of phytochrome includes alterations in the levels of gibberellin (GA) and abscisic acid (ABA). To determine the molecular mechanism of phytochrome regulation of ABA metabolism, we isolated four lettuce cDNAs encoding 9-cis-epoxycarotenoid dioxygenase ( biosynthesis; LsNCED1-LsNCED4) and four cDNAs for ABA 8'-hydroxylase (catabolism; LsABA8ox1-LsABA8ox4). Measurements of ABA and its catabolites showed that a decrease in ABA level coincided with a slight increase in the level of the ABA catabolite phaseic acid after red light treatment. Quantitative reverse transcription-polymerase chain reaction analysis indicated that ABA levels are controlled by phytochrome through down-regulation of LsNCED2 and LsNCED4 expression and up-regulation of LsABA8ox4 expression in lettuce seeds. Furthermore, the expression levels of LsNCED4 decreased after GA 1 treatment, whereas the levels of expression of the other two genes were unaffected. The LsNCED4 expression was also down-regulated by red light in lettuce seeds in which GA biosynthesis was suppressed by AMO-1618, a specific GA biosynthesis inhibitor. These results indicate that phytochrome regulation of ABA metabolism is mediated by both GA-dependent and -independent mechanisms. Spatial analysis showed that after red light treatment, the ABA decrease on the hypocotyl side was greater than that on the cotyledon side of lettuce seeds. Moreover, phytochrome-regulated expression of ABA and GA biosynthesis genes was observed on the hypocotyl side, rather than the cotyledon side, suggesting that this regulation occurs near the photo-perceptive site.