Commonwealth Scientific and Industrial Research Organization Division of Plant Industry, Canberra, Australian Capital Territory 2601, Australia.
Plant Physiol. 2012 Sep;160(1):308-18. doi: 10.1104/pp.112.197954. Epub 2012 Jul 12.
Tillering (branching) is a major yield component and, therefore, a target for improving the yield of crops. However, tillering is regulated by complex interactions of endogenous and environmental signals, and the knowledge required to achieve optimal tiller number through genetic and agronomic means is still lacking. Regulatory mechanisms may be revealed through physiological and molecular characterization of naturally occurring and induced tillering mutants in the major crops. Here we characterize a reduced tillering (tin, for tiller inhibition) mutant of wheat (Triticum aestivum). The reduced tillering in tin is due to early cessation of tiller bud outgrowth during the transition of the shoot apex from the vegetative to the reproductive stage. There was no observed difference in the development of the main stem shoot apex between tin and the wild type. However, tin initiated internode development earlier and, unlike the wild type, the basal internodes in tin were solid rather than hollow. We hypothesize that tin represents a novel type of reduced tillering mutant associated with precocious internode elongation that diverts sucrose (Suc) away from developing tillers. Consistent with this hypothesis, we have observed upregulation of a gene induced by Suc starvation, downregulation of a Suc-inducible gene, and a reduced Suc content in dormant tin buds. The increased expression of the wheat Dormancy-associated (DRM1-like) and Teosinte Branched1 (TB1-like) genes and the reduced expression of cell cycle genes also indicate bud dormancy in tin. These results highlight the significance of Suc in shoot branching and the possibility of optimizing tillering by manipulating the timing of internode elongation.
分蘖（分枝）是产量的主要组成部分，因此也是提高作物产量的目标。然而，分蘖受内源性和环境信号的复杂相互作用调控，通过遗传和农艺手段实现最佳分蘖数所需的知识仍然缺乏。通过对主要作物中自然发生和诱导的分蘖突变体的生理和分子特征分析，可以揭示调控机制。在这里，我们对小麦（Triticum aestivum）的分蘖减少（tin，意为分蘖抑制）突变体进行了描述。tin 的分蘖减少是由于在茎尖从营养生长向生殖生长过渡期间，分蘖芽的生长提前停止。tin 和野生型之间主茎尖的发育没有观察到差异。然而，tin 更早地启动了节间发育，与野生型不同，tin 的基部节间是实心的而不是空心的。我们假设 tin 代表了一种与早熟节间伸长相关的新型分蘖减少突变体，它将蔗糖（Suc）从发育中的分蘖转移走。与这一假设一致，我们观察到了对 Suc 饥饿诱导的基因的上调表达、对 Suc 诱导基因的下调表达以及休眠 tin 芽中 Suc 含量的降低。休眠相关（DRM1 样）和玉米分枝 1（TB1 样）基因表达的增加以及细胞周期基因表达的减少也表明 tin 中的芽休眠。这些结果突出了 Suc 在分枝中的重要性，以及通过操纵节间伸长的时间来优化分蘖的可能性。
