Molecular Plant Science/Plant Biochemistry, University of Wuppertal, Gaußstr. 20, Wuppertal, Germany.
Clinic for General Pediatrics, Neonatology and Paediatric Cardiology, University Clinic Düsseldorf, Moorenstr. 5, Düsseldorf, Germany.
Tree Physiol. 2019 Feb 1;39(2):284-299. doi: 10.1093/treephys/tpy120.
In temperate woody species, carbon transport from source to sink tissues is a striking physiological process, particularly considering seasonal changes. The functions of different tissues can also alternate across the seasons. In this regard, phloem loading and sugar distribution are important aspects of carbon partitioning, and sucrose uptake transporters (SUTs) play a key role in these processes. Therefore, the influence of seasons and different light-dark conditions on the expression of SUTs from 3-year-old Fagus sylvatica L., Quercus robur L. and Picea abies (L.) Karst. trees were analyzed. In addition, tissue-specific sugar and starch contents under these different environmental conditions were determined. Putative SUTs were identified in the gymnosperms (Picea abies, Ginkgo biloba L.), here for the first time, and also in the angiosperms (Q. robur, F. sylvatica). The identified SUT sequences of the different tree species cluster into three types, similar to other SUTs from herbaceous and tree species. Furthermore, the sequences from angiosperm and those from gymnosperm species form distinct clusters within the three types of SUTs. In F. sylvatica, Q. robur and P. abies, the expression levels of the different SUTs during seasons showed marked variations. Because of the high expression levels of type I SUTs in bark, wood and leaves during active growing phases in spring and summer, it can be assumed that they are involved in phloem loading, sucrose retrieval and possibly in further physiological processes. The expression patterns also indicate a flexible expression in all tissues depending on physiological requirements and environmental conditions. Compared with type I SUTs, the seasonal variations of type II SUT expression were less pronounced, whereas the seasonal variations of the type III SUT expression patterns were partly reverse. In addition to the seasonal regulation, the expressions of the different SUTs were also regulated by light in a diurnal manner.
在温带木本植物中，碳从源组织到汇组织的运输是一个显著的生理过程，尤其是考虑到季节性变化。不同组织的功能也会随着季节的变化而交替。在这方面，韧皮部装载和糖分配是碳分配的重要方面，而蔗糖摄取转运蛋白（SUTs）在这些过程中起着关键作用。因此，分析了 3 年生欧洲山毛榉、欧洲栎和挪威云杉树木在不同季节和不同光暗条件下 SUT 的表达情况。此外，还测定了这些不同环境条件下组织特异性糖和淀粉的含量。首次在裸子植物（挪威云杉、银杏）和被子植物（欧洲栎、欧洲山毛榉）中鉴定了推定的 SUT。不同树种的鉴定 SUT 序列分为三类，与草本和木本物种的其他 SUT 相似。此外，被子植物和裸子植物的序列在三类 SUT 中形成明显的聚类。在欧洲山毛榉、欧洲栎和挪威云杉中，不同 SUT 在季节间的表达水平表现出明显的变化。由于 I 型 SUT 在树皮、木材和叶片中的高表达水平在春夏季的活跃生长阶段，因此可以假设它们参与韧皮部装载、蔗糖回收，可能还参与进一步的生理过程。表达模式还表明，所有组织都根据生理需求和环境条件表现出灵活的表达。与 I 型 SUT 相比，II 型 SUT 表达的季节性变化不太明显，而 III 型 SUT 表达模式的季节性变化部分相反。除了季节性调节外，不同 SUT 的表达还受到昼夜节律的光调节。
