Research Department of Genetics, Evolution, and Environment, University College London, London WC1E 6BT, United Kingdom.
Plant Physiol. 2012 Mar;158(3):1241-51. doi: 10.1104/pp.111.191908. Epub 2012 Jan 13.
Trehalose 6-phosphate (T6P) is an important regulator of plant metabolism and development. T6P content increases when carbon availability is high, and in young growing tissue, T6P inhibits the activity of Snf1-related protein kinase (SnRK1). Here, strong accumulation of T6P was found in senescing leaves of Arabidopsis (Arabidopsis thaliana), in parallel with a rise in sugar contents. To determine the role of T6P in senescence, T6P content was altered by expressing the bacterial T6P synthase gene, otsA (to increase T6P), or the T6P phosphatase gene, otsB (to decrease T6P). In otsB-expressing plants, T6P accumulated less strongly during senescence than in wild-type plants, while otsA-expressing plants contained more T6P throughout. Mature otsB-expressing plants showed a similar phenotype as described for plants overexpressing the SnRK1 gene, KIN10, including reduced anthocyanin accumulation and delayed senescence. This was confirmed by quantitative reverse transcription-polymerase chain reaction analysis of senescence-associated genes and genes involved in anthocyanin synthesis. To analyze if the senescence phenotype was due to decreased sugar sensitivity, the response to sugars was determined. In combination with low nitrogen supply, metabolizable sugars (glucose, fructose, or sucrose) induced senescence in wild-type and otsA-expressing plants but to a smaller extent in otsB-expressing plants. The sugar analog 3-O-methyl glucose, on the other hand, did not induce senescence in any of the lines. Transfer of plants to and from glucose-containing medium suggested that glucose determines senescence during late development but that the effects of T6P on senescence are established by the sugar response of young plants.
海藻糖-6-磷酸（T6P）是植物代谢和发育的重要调节剂。当碳源供应充足且在幼嫩的生长组织中时，T6P 含量增加，T6P 会抑制 Snf1 相关蛋白激酶（SnRK1）的活性。在这里，拟南芥（Arabidopsis thaliana）衰老叶片中 T6P 积累量增加，与糖含量升高平行。为了确定 T6P 在衰老过程中的作用，通过表达细菌 T6P 合酶基因 otsA（增加 T6P）或 T6P 磷酸酶基因 otsB（减少 T6P）来改变 T6P 的含量。在 otsB 表达植株中，T6P 在衰老过程中的积累强度弱于野生型植株，而 otsA 表达植株中则始终含有更多的 T6P。成熟 otsB 表达植株表现出与过量表达 SnRK1 基因 KIN10 的植株相似的表型，包括花青素积累减少和衰老延迟。这通过对衰老相关基因和参与花青素合成的基因的定量逆转录聚合酶链反应分析得到了证实。为了分析衰老表型是否是由于糖敏感性降低引起的，测定了对糖的反应。在低氮供应的情况下，可代谢糖（葡萄糖、果糖或蔗糖）诱导野生型和 otsA 表达植株衰老，但在 otsB 表达植株中诱导衰老的程度较小。另一方面，糖类似物 3-O-甲基葡萄糖在任何品系中均未诱导衰老。将植物从含葡萄糖的培养基中转移到无葡萄糖的培养基中，然后再转移回来，表明葡萄糖在后期发育过程中决定衰老，但 T6P 对衰老的影响是由幼嫩植物对糖的反应建立的。
