Department of Postharvest Science of Fresh Produce, The Volcani Center, Agricultural Research Organization, Rishon LeZion 7528809, Israel.
Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, Hebrew University of Jerusalem, Robert H. Smith Faculty of Agriculture, Food, and Environment, Rehovot 76100, Israel.
Plant Physiol. 2017 Oct;175(2):734-745. doi: 10.1104/pp.17.00995. Epub 2017 Aug 31.
The potato () tuber is a swollen stem. Sprouts growing from the tuber nodes represent loss of apical dominance and branching. Long cold storage induces loss of tuber apical dominance and results in secondary branching. Here, we show that a similar branching pattern can be induced by short heat treatment of the tubers. Detached sprouts were induced to branch by the heat treatment only when attached to a parenchyma cylinder. Grafting experiments showed that the scion branches only when grafted onto heat- or cold-treated tuber parenchyma, suggesting that the branching signal is transmitted systemically from the bud-base parenchyma to the grafted stem. Exogenous supply of sucrose (Suc), glucose, or fructose solution to detached sprouts induced branching in a dose-responsive manner, and an increase in Suc level was observed in tuber parenchyma upon branching induction, suggesting a role for elevated parenchyma sugars in the regulation of branching. However, sugar analysis of the apex and node after grafting showed no distinct differences in sugar levels between branching and nonbranching stems. Vacuolar invertase is a key enzyme in determining the level of Suc and its cleavage products, glucose and fructose, in potato parenchyma. Silencing of the vacuolar invertase-encoding gene led to increased tuber branching in combination with branching-inducing treatments. These results suggest that Suc in the parenchyma induces branching through signaling and not by excess mobilization from the parenchyma to the stem.
马铃薯（）块茎是一种膨胀的茎。从块茎节点生长的芽表示顶端优势的丧失和分枝。长期低温贮藏会导致块茎顶端优势丧失，导致次生分枝。在这里，我们表明，短时间的热处理也可以诱导类似的分枝模式。只有当附着在薄壁组织圆柱上时，离体芽才能通过热处理诱导分枝。嫁接实验表明，接穗仅在嫁接于热处理或冷处理的块茎薄壁组织上时才分枝，这表明分枝信号从芽基薄壁组织系统地传递到嫁接的茎上。将蔗糖（Suc）、葡萄糖或果糖溶液外施于离体芽中，以剂量反应方式诱导分枝，并且在诱导分枝时观察到块茎薄壁组织中 Suc 水平增加，这表明升高的薄壁组织糖在分枝调控中起作用。然而，嫁接后对顶端和节点的糖分析显示，分枝和非分枝茎之间的糖水平没有明显差异。液泡转化酶是决定马铃薯薄壁组织中 Suc 及其裂解产物葡萄糖和果糖水平的关键酶。液泡转化酶编码基因的沉默导致块茎分枝增加，并与诱导分枝的处理相结合。这些结果表明，薄壁组织中的 Suc 通过信号而不是通过从薄壁组织向茎的过度动员来诱导分枝。
