Group-C/S1 bZIP heterodimers regulate MdIPT5b to negatively modulate drought tolerance in apple species
Group-C/S1 bZIP heterodimers regulate MdIPT5b to negatively modulate drought tolerance in apple species
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C/S1 组 bZIP 异二聚体调节 MdIPT5b 以负向调节苹果物种的耐旱性
DOI：
10.1111/tpj.15296
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发表时间：
2021-05-16
期刊：
影响因子：
7.2
通讯作者：
Han, Zhenhai
中科院分区：
文献类型：
--
作者：
Feng, Yi;Wang, Yi;Han, Zhenhai
细胞分裂素在延缓衰老、减少氧化损伤和维持植物生长方面起着重要作用。本研究表明，细胞分裂素代谢关键酶MdIPT 5 b基因的异位表达，通过维持细胞分裂素的稳态，从而维持氧化还原平衡，提高了转基因苹果（Malus acutica）愈伤组织和番茄（Solanum lycopersicum）幼苗的耐旱性。在限制灌溉制度下，转基因番茄植株的产量得到提高。C/S1 bZIP的异源二聚体参与细胞分裂素介导的干旱反应。异二聚体结合MdIPT 5 b启动子的ProRE，从而直接抑制基因转录。单个C/S1 bZIP成员不能独立地作为抑制子。然而，特定的配对成员（MdbZIP 80与MdbZIP 2或与MdbZIP 39的异二聚体）有效地抑制转录。α-螺旋结构对于C/S1 bZIP成员的异源二聚化和协同转录抑制是必不可少的。作为耐旱性的负调节因子，单独抑制MdbZIP 2或MdbZIP 39不能提高MdIPT 5 b的表达，也不能提高转基因苹果愈伤组织的耐旱性。但是，当它们被共同压制时，这可以实现。单独抑制MdbZIP 80可以提高MdIPT 5 b的表达，提高转基因苹果愈伤组织的耐旱性。然而，这些作用在MdbZIP 80和MdIPT 5 b的共抑制下被逆转。在苹果叶片延迟暗诱导衰老过程中也观察到类似的结果。总之，苹果C/S1 bZIP网络（涉及MdbZIP 2，MdbZIP 39和MdbZIP 80）直接抑制MdIPT 5 b的表达，从而以功能冗余的方式负调节耐旱性和黑暗诱导的衰老。
Cytokinins play a central role in delaying senescence, reducing oxidative damage and maintaining plant growth during drought. This study showed that the ectopic expression of ProRE-deleted MdIPT5b, a key enzyme involved in cytokinin metabolism, increased the drought tolerance of transgenic Malus domestica (apple) callus and Solanum lycopersicum (tomato) seedlings by maintaining cytokinin homeostasis, and thus maintaining redox balance. Under restricted watering regimes, the yields of transgenic tomato plants were enhanced. Heterodimers of C/S1 bZIP are involved in the cytokinin-mediated drought response. The heterodimers bind the ProRE of MdIPT5b promoter, thus directly suppressing gene transcription. Single C/S1 bZIP members could not independently function as suppressors. However, specific paired members (heterodimers of MdbZIP80 with MdbZIP2 or with MdbZIP39) effectively suppressed transcription. The alpha-helical structure is essential for the heterodimerization of C/S1 bZIP members and for synergistic transcriptional suppression. As negative regulators of drought tolerance, suppressing either MdbZIP2 or MdbZIP39 alone does not improve the expression of MdIPT5b and did not increase the drought tolerance of transgenic apple callus. However, this could be achieved when they were co-suppressed. The suppression of MdbZIP80 alone could improve MdIPT5b expression and increase the drought tolerance of transgenic apple callus. However, these effects were reversed in response to the cosuppression of MdbZIP80 and MdIPT5b. Similar results were also observed during delayed dark-induced senescence in apple leaves. In conclusion, the apple C/S1 bZIP network (involving MdbZIP2, MdbZIP39 and MdbZIP80) directly suppressed the expression of MdIPT5b, thus negatively modulating drought tolerance and dark-induced senescence in a functionally redundant manner.