School of Biological, Earth & Environmental Sciences and Environmental Research Institute, University College Cork, Distillery Fields, Cork.
Physiol Plant. 2022 Mar;174(2):e13656. doi: 10.1111/ppl.13656.
Plant growth and development depend on the availability of carbohydrates synthesised in photosynthesis (source activity) and utilisation of these carbohydrates for growth (sink activity). External conditions, such as temperature, nutrient availability and stress, can affect source as well as sink activity. Optimal utilisation of resources is under circadian clock control. This molecular timekeeper ensures that growth responses are adjusted to different photoperiod and temperature settings by modulating starch accumulation and degradation accordingly. For example, during the night, starch degradation is required to provide sugars for growth. Under favourable growth conditions, high sugar availability stimulates growth and development, resulting in an overall accelerated life cycle of annual plants. Key signalling components include trehalose-6-phosphate (Tre6P), which reflects sucrose availability and stimulates growth and branching when the conditions are favourable. Under sink limitation, Tre6P does, however, inhibit night-time starch degradation. Tre6P interacts with Sucrose-non-fermenting1-Related Kinase1 (SnRK1), a protein kinase that inhibits growth under starvation and stress conditions and delays development (including flowering and senescence). Tre6P inhibits SnRK1 activity, but SnRK1 increases the Tre6P to sucrose ratio under favourable conditions. Alongside Tre6P, Target of Rapamycin (TOR) stimulates processes such as protein synthesis and growth when sugar availability is high. In annual plants, an accelerated life cycle results in early leaf and plant senescence, thus shortening the lifespan. While the availability of carbohydrates in the form of sucrose and other sugars also plays an important role in seasonal life cycle events (phenology) of perennial plants, the sugar signalling pathways in perennials are less well understood.
植物的生长和发育依赖于光合作用（源活动）中合成的碳水化合物的可用性，以及这些碳水化合物用于生长（汇活动）的利用。外部条件，如温度、养分供应和胁迫，会影响源和汇的活性。资源的最佳利用受生物钟控制。这个分子时钟确保通过相应地调节淀粉积累和降解，使生长反应适应不同的光周期和温度设置。例如，在夜间，需要淀粉降解为生长提供糖分。在有利的生长条件下，高糖可用性会刺激生长和发育，导致一年生植物的整个生命周期加速。关键的信号成分包括海藻糖-6-磷酸（Tre6P），它反映了蔗糖的可用性，并在条件有利时刺激生长和分枝。在汇限制下，Tre6P 会抑制夜间淀粉降解。Tre6P 与蔗糖非发酵 1 相关激酶 1（SnRK1）相互作用，SnRK1 是一种蛋白激酶，在饥饿和胁迫条件下抑制生长并延迟发育（包括开花和衰老）。Tre6P 抑制 SnRK1 活性，但 SnRK1 在有利条件下增加 Tre6P 与蔗糖的比例。除了 Tre6P，雷帕霉素靶蛋白（TOR）在糖可用性高时刺激蛋白质合成和生长等过程。在一年生植物中，加速的生命周期导致早期叶片和植物衰老，从而缩短寿命。虽然以蔗糖和其他糖形式存在的碳水化合物在多年生植物的季节性生命周期事件（物候学）中也起着重要作用，但多年生植物中的糖信号通路了解较少。
