Seasonal Abscisic Acid Signal and a Basic Leucine Zipper Transcription Factor, DkbZIP5, Regulate Proanthocyanidin Biosynthesis in Persimmon Fruit
Seasonal Abscisic Acid Signal and a Basic Leucine Zipper Transcription Factor, DkbZIP5, Regulate Proanthocyanidin Biosynthesis in Persimmon Fruit
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DOI：
10.1104/pp.111.191205
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发表时间：
2012-02-01
期刊：
影响因子：
7.4
通讯作者：
Yonemori, Keizo
中科院分区：
文献类型：
--
作者：
Akagi, Takashi;Katayama-Ikegami, Ayako;Yonemori, Keizo
原花青素(PAS)是植物保护和作物品质的次生代谢产物。柿(Diospyros Kaki)有一个独特的特点，就是积累了大量的PA，特别是在它的果实中。DkMyb4是一种Myb转录因子(Tf)，调节着柿中许多PA途径基因的表达，正常和突变的非收敛型果实表现出不同的PA积累模式。本研究试图找出影响DkMyb4在柿果实中表达和PA积累的相关因素。脱落酸(ABA)和ABA生物合成抑制剂处理导致DkMyb4和PA生物合成在苦涩和非苦涩果实中的表达模式随发育阶段的不同而不同。为了获得ABA信号转运蛋白，我们分离了一个在柿果实中高表达的全长碱性亮氨酸拉链转运蛋白(BZIP)转运蛋白DkbZIP5。我们还发现，异源DkbZIP5在柿愈伤组织中的过表达诱导了DkMyb4的上调和PA的生物合成。此外，通过凝胶迁移率改变分析和瞬时报告实验对DkbZIP5进行了详细的分子表征，结果表明DkbZIP5能够识别DkMyb4启动子区域的ABA反应元件，并以ABA依赖的方式直接调控DkMyb4。这些结果表明，ABA信号可能通过DkbZIP5激活DkMyb4参与了柿果实PA的生物合成。
Proanthocyanidins (PAs) are secondary metabolites that contribute to plant protection and crop quality. Persimmon (Diospyros kaki) has a unique characteristic of accumulating large amounts of PAs, particularly in its fruit. Normal astringent-type and mutant nonastringent-type fruits show different PA accumulation patterns depending on the seasonal expression patterns of DkMyb4, which is a Myb transcription factor (TF) regulating many PA pathway genes in persimmon. In this study, attempts were made to identify the factors involved in DkMyb4 expression and the resultant PA accumulation in persimmon fruit. Treatment with abscisic acid (ABA) and an ABA biosynthesis inhibitor resulted in differential changes in the expression patterns of DkMyb4 and PA biosynthesis in astringent-type and nonastringent-type fruits depending on the development stage. To obtain an ABA-signaling TF, we isolated a full-length basic leucine zipper (bZIP) TF, DkbZIP5, which is highly expressed in persimmon fruit. We also showed that ectopic DkbZIP5 overexpression in persimmon calluses induced the up-regulation of DkMyb4 and the resultant PA biosynthesis. In addition, a detailed molecular characterization using the electrophoretic mobility shift assay and transient reporter assay indicated that DkbZIP5 recognized ABA-responsive elements in the promoter region of DkMyb4 and acted as a direct regulator of DkMyb4 in an ABA-dependent manner. These results suggest that ABA signals may be involved in PA biosynthesis in persimmon fruit via DkMyb4 activation by DkbZIP5.