Regulation of hormone metabolism in Arabidopsis seeds: phytochrome regulation of abscisic acid metabolism and abscisic acid regulation of gibberellin metabolism
Regulation of hormone metabolism in Arabidopsis seeds: phytochrome regulation of abscisic acid metabolism and abscisic acid regulation of gibberellin metabolism
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DOI：
10.1111/j.1365-313x.2006.02881.x
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发表时间：
2006-11-01
期刊：
影响因子：
7.2
通讯作者：
Nambara, Eiji
中科院分区：
文献类型：
--
作者：
Seo, Mitsunori;Hanada, Atsushi;Nambara, Eiji
在广泛的植物物种中，种子萌发受到两种植物激素--脱落酸(ABA)和赤霉素(GA)的拮抗调节。在本研究中，我们揭示了ABA代谢(包括生物合成和失活)在拟南芥光可逆种子萌发过程中以与GA代谢相反的方式受到光敏色素的调节。经远红光脉冲处理的暗吸胀种子经红光脉冲照射后，内源ABA水平降低，而光敏色素B(PHYB)缺失突变体的内源ABA水平下降受到抑制。ABA生物合成基因AtNCED6和失活基因CyP707A2的表达受光可逆调控，表明这两个基因在PHYB介导的ABA代谢调控中起关键作用。脱落酸缺失突变体如nced6-1、aba2-2和aao3-4在FR光脉冲照射后的黑暗中萌发能力比野生型强。此外，突变体aba2-2的GA合成能力较野生型在FR光脉冲后的暗吸胀过程中有所提高。在种子发育过程中，还观察到了突变体aba2-2中GA生物合成的激活。这些数据表明，ABA参与了种子吸胀和发育过程中GA生物合成的抑制。在吸胀和发育过程中，负责ABA生物合成最后两步的AtABA2和AA03基因与GA生物合成基因AtGA3ox2的空间表达模式不同，这表明种子中ABA和GA的生物合成发生在不同的细胞类型中。
In a wide range of plant species, seed germination is regulated antagonistically by two plant hormones, abscisic acid (ABA) and gibberellin (GA). In the present study, we have revealed that ABA metabolism (both biosynthesis and inactivation) was phytochrome-regulated in an opposite fashion to GA metabolism during photoreversible seed germination in Arabidopsis. Endogenous ABA levels were decreased by irradiation with a red (R) light pulse in dark-imbibed seeds pre-treated with a far-red (FR) light pulse, and the reduction in ABA levels in response to R light was inhibited in a phytochrome B (PHYB)-deficient mutant. Expression of an ABA biosynthesis gene, AtNCED6, and the inactivation gene, CYP707A2, was regulated in a photoreversible manner, suggesting a key role for the genes in PHYB-mediated regulation of ABA metabolism. Abscisic acid-deficient mutants such as nced6-1, aba2-2 and aao3-4 exhibited an enhanced ability to germinate relative to wild type when imbibed in the dark after irradiation with an FR light pulse. In addition, the ability to synthesize GA was improved in the aba2-2 mutant compared with wild type during dark-imbibition after an FR light pulse. Activation of GA biosynthesis in the aba2-2 mutant was also observed during seed development. These data indicate that ABA is involved in the suppression of GA biosynthesis in both imbibed and developing seeds. Spatial expression patterns of the AtABA2 and AAO3 genes, responsible for last two steps of ABA biosynthesis, were distinct from that of the GA biosynthesis gene, AtGA3ox2, in both imbibed and developing seeds, suggesting that biosynthesis of ABA and GA in seeds occurs in different cell types.