ARC Centre of Excellence for Plant Success in Nature and Agriculture, School of Biological Sciences, The University of Queensland, Brisbane, QLD 4072, Australia.
School of Biological Sciences, The University of Queensland, Brisbane, QLD 4072, Australia.
Plant Physiol. 2023 May 31;192(2):1420-1434. doi: 10.1093/plphys/kiad034.
The inhibition of shoot branching by the growing shoot tip of plants, termed apical dominance, was originally thought to be mediated by auxin. Recently, the importance of the shoot tip sink strength during apical dominance has re-emerged with recent studies highlighting roles for sugars in promoting branching. This raises many unanswered questions on the relative roles of auxin and sugars in apical dominance. Here we show that auxin depletion after decapitation is not always the initial trigger of rapid cytokinin (CK) increases in buds that are instead correlated with enhanced sugars. Auxin may also act through strigolactones (SLs) which have been shown to suppress branching after decapitation, but here we show that SLs do not have a significant effect on initial bud outgrowth after decapitation. We report here that when sucrose or CK is abundant, SLs are less inhibitory during the bud release stage compared to during later stages and that SL treatment rapidly inhibits CK accumulation in pea (Pisum sativum) axillary buds of intact plants. After initial bud release, we find an important role of gibberellin (GA) in promoting sustained bud growth downstream of auxin. We are, therefore, able to suggest a model of apical dominance that integrates auxin, sucrose, SLs, CKs, and GAs and describes differences in signalling across stages of bud release to sustained growth.
植物顶芽对侧芽生长的抑制作用，即顶端优势，最初被认为是由生长素介导的。最近，顶端优势过程中顶芽库强的重要性重新引起了人们的关注，最近的研究强调了糖在促进分枝中的作用。这就提出了许多关于生长素和糖在顶端优势中的相对作用的未解决的问题。在这里，我们表明，去顶后生长素的耗竭并不总是导致芽中快速细胞分裂素（CK）增加的最初触发因素，而是与增强的糖有关。生长素也可能通过独脚金内酯（SLs）起作用，SLs 已被证明在去顶后抑制分枝，但在这里我们表明，SLs 对去顶后芽初始生长没有显著影响。我们在这里报告，当蔗糖或 CK 丰富时，与后期阶段相比，SLs 在芽释放阶段的抑制作用较小，并且 SL 处理可迅速抑制完整植株豌豆（Pisum sativum）腋芽中 CK 的积累。在初始芽释放后，我们发现 GA 在促进生长素下游芽持续生长中起着重要作用。因此，我们能够提出一个整合生长素、蔗糖、SLs、CKs 和 GAs 的顶端优势模型，并描述了芽释放到持续生长各个阶段信号转导的差异。
