Dual Role of Gibberellin in Perennial Shoot Branching: Inhibition and Activation
Dual Role of Gibberellin in Perennial Shoot Branching: Inhibition and Activation
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DOI：
10.3389/fpls.2020.00736
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发表时间：
2020-06-05
影响因子：
5.6
通讯作者：
van der Schoot, Christiaan
中科院分区：
文献类型：
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作者：
Katyayini, Niveditha Umesh;Rinne, Paivi L. H.;van der Schoot, Christiaan
腋芽分枝（AXBs）是由一个网络的抑制和促进力量，其中包括激素。在多年生植物中，AXBs内的胚芽的矮小身材表明赤霉素（GA）缺乏，这表明AXB的激活和生长需要GA。尽管如此，GA在分支中的作用仍然不清楚。我们在这里进行了全面的GA转录和代谢产物的分析，在混合白杨，多年生分枝模型。结果表明，GA对分枝既有促进作用，又有抑制作用。后者分两个阶段执行。虽然GA2ox在静止AXB中表达水平较高，但去头后其表达迅速下调，这意味着GA信号增强。在第二阶段，GA3ox2介导的novoGA-生物合成在AXB伸长之前的12和24小时之间开始。代谢物分析表明，GA（1/4）水平通常在增殖的顶端高，在发育不活跃的静止AXB中低，而GA（3/6）则相反。为了研究AXB是否受到GA（3），GA（4）和GR 24（分支抑制激素独脚金内酯的类似物）的不同影响，将它们喂入单节插条的AXB中。GA（3）和GA（4）对GA和SL途径基因的影响相似，但关键是GA（3）诱导AXB的表达，而GA（4）促进生长。GA（3）和GA（4）均强烈上调GA_（2ox）基因，使GA（1/4）失活，但不使GA（3/6）失活。因此，在静止AXB中观察到的GA（3/6）的产生靶向GA（1/4）用于GA 2ox介导的失活。因此，AXB静止可以通过GA（3/6）与独脚金内酯的组合来维持。我们发现GA（3）和GA（4）在AXB激活中的不同任务可能解释了为什么GA在分支中的作用一直难以破译。总之，这些结果支持了一种新的范例，其中GA（3/6）在静止AXB中维持高水平的GA 2ox表达和低水平的GA（4），而激活和生长需要通过快速减少GA失活和随后的GA生物合成来增加GA（1/4）信号传导。
Shoot branching from axillary buds (AXBs) is regulated by a network of inhibitory and promotive forces, which includes hormones. In perennials, the dwarfed stature of the embryonic shoot inside AXBs is indicative of gibberellin (GA) deficiency, suggesting that AXB activation and outgrowth require GA. Nonetheless, the role of GA in branching has remained obscure. We here carried out comprehensive GA transcript and metabolite analyses in hybrid aspen, a perennial branching model. The results indicate that GA has an inhibitory as well as promotive role in branching. The latter is executed in two phases. While the expression level ofGA2oxis high in quiescent AXBs, decapitation rapidly downregulated it, implying increased GA signaling. In the second phase,GA3ox2-mediatedde novoGA-biosynthesis is initiated between 12 and 24 h, prior to AXB elongation. Metabolite analyzes showed that GA(1/4)levels were typically high in proliferating apices and low in the developmentally inactive, quiescent AXBs, whereas the reverse was true for GA(3/6). To investigate if AXBs are differently affected by GA(3), GA(4), and GR24, an analog of the branch-inhibitor hormone strigolactone, they were fed into AXBs of single-node cuttings. GA(3)and GA(4)had similar effects on GA and SL pathway genes, but crucially GA(3)induced AXB abscission whereas GA(4)promoted outgrowth. Both GA(3)and GA(4)strongly upregulatedGA2ox genes, which deactivate GA(1/4)but not GA(3/6). Thus, the observed production of GA(3/6)in quiescent AXBs targets GA(1/4)for GA2ox-mediated deactivation. AXB quiescence can therefore be maintained by GA(3/6), in combination with strigolactone. Our discovery of the distinct tasks of GA(3)and GA(4)in AXB activation might explain why the role of GA in branching has been difficult to decipher. Together, the results support a novel paradigm in which GA(3/6)maintains high levels ofGA2oxexpression and low levels of GA(4)in quiescent AXBs, whereas activation and outgrowth require increased GA(1/4)signaling through the rapid reduction of GA deactivation and subsequent GA biosynthesis.