Centro de Biologia Molecular e Engenharia Genética, Universidade Estadual de Campinas, Cidade Universitária Zeferino Vaz, CP6010 Campinas, Sao Paulo, Brazil.
Plant Physiol. 2011 Oct;157(2):692-705. doi: 10.1104/pp.111.181743. Epub 2011 Aug 15.
Glucose modulates plant metabolism, growth, and development. In Arabidopsis (Arabidopsis thaliana), Hexokinase1 (HXK1) is a glucose sensor that may trigger abscisic acid (ABA) synthesis and sensitivity to mediate glucose-induced inhibition of seedling development. Here, we show that the intensity of short-term responses to glucose can vary with ABA activity. We report that the transient (2 h/4 h) repression by 2% glucose of AtbZIP63, a gene encoding a basic-leucine zipper (bZIP) transcription factor partially involved in the Snf1-related kinase KIN10-induced responses to energy limitation, is independent of HXK1 and is not mediated by changes in ABA levels. However, high-concentration (6%) glucose-mediated repression appears to be modulated by ABA, since full repression of AtbZIP63 requires a functional ABA biosynthetic pathway. Furthermore, the combination of glucose and ABA was able to trigger a synergistic repression of AtbZIP63 and its homologue AtbZIP3, revealing a shared regulatory feature consisting of the modulation of glucose sensitivity by ABA. The synergistic regulation of AtbZIP63 was not reproduced by an AtbZIP63 promoter-5'-untranslated region::β-glucuronidase fusion, thus suggesting possible posttranscriptional control. A transcriptional inhibition assay with cordycepin provided further evidence for the regulation of mRNA decay in response to glucose plus ABA. Overall, these results indicate that AtbZIP63 is an important node of the glucose-ABA interaction network. The mechanisms by which AtbZIP63 may participate in the fine-tuning of ABA-mediated abiotic stress responses according to sugar availability (i.e., energy status) are discussed.
葡萄糖调节植物代谢、生长和发育。在拟南芥（Arabidopsis thaliana）中，己糖激酶 1（HXK1）是一种葡萄糖传感器，可能触发脱落酸（ABA）的合成和敏感性，以介导葡萄糖诱导的幼苗发育抑制。在这里，我们表明，对葡萄糖的短期反应强度可能因 ABA 活性而异。我们报告说，2%葡萄糖对 AtbZIP63 的瞬时（2 h/4 h）抑制，AtbZIP63 基因编码一种碱性亮氨酸拉链（bZIP）转录因子，部分参与了与能量限制有关的 Snf1 相关激酶 KIN10 的反应，这与 HXK1 无关，也不是通过 ABA 水平的变化介导的。然而，高浓度（6%）葡萄糖介导的抑制似乎受 ABA 调节，因为 AtbZIP63 的完全抑制需要一个功能性的 ABA 生物合成途径。此外，葡萄糖和 ABA 的组合能够触发 AtbZIP63 和其同源物 AtbZIP3 的协同抑制，揭示了一种由 ABA 调节葡萄糖敏感性的共同调节特征。AtbZIP63 的协同调节不能由 AtbZIP63 启动子 5'-非翻译区::β-葡聚糖酶融合来复制，因此暗示可能存在转录后控制。用 cordycepin 进行的转录抑制测定进一步提供了响应葡萄糖加 ABA 调节 mRNA 降解的证据。总的来说，这些结果表明 AtbZIP63 是葡萄糖-ABA 相互作用网络的一个重要节点。讨论了 AtbZIP63 根据糖可用性（即能量状态）参与精细调节 ABA 介导的非生物胁迫反应的机制。
