期刊
PLANT JOURNAL
卷 107, 期 3, 页码 688-697出版社
WILEY
DOI: 10.1111/tpj.15359
关键词
starch granules; starch metabolism; starch granule initiation; starch granule number per chloroplast; starch morphology; Arabidopsis thaliana
资金
- Deutsche Forschungsgemeinschaft [DFG-FE 1030/2-1, DFG-FE 1030/5-1, DFG-FE 1030/6-1, PGC2018-096851-B-C22]
- Spanish Ministry of Science and Innovation (MICINN)
- European Fund for Regional Development
This review discusses the initiation of starch granule formation and the controlling mechanism of granule numbers per plastid. It highlights the importance of polypeptides in providing support for starch granule formation and the strict regulation of granule numbers.
The initiation of starch granule formation and the mechanism controlling the number of granules per plastid have been some of the most elusive aspects of starch metabolism. This review covers the advances made in the study of these processes. The analyses presented herein depict a scenario in which starch synthase isoform 4 (SS4) provides the elongating activity necessary for the initiation of starch granule formation. However, this protein does not act alone; other polypeptides are required for the initiation of an appropriate number of starch granules per chloroplast. The functions of this group of polypeptides include providing suitable substrates (maltooligosaccharides) to SS4, the localization of the starch initiation machinery to the thylakoid membranes, and facilitating the correct folding of SS4. The number of starch granules per chloroplast is tightly regulated and depends on the developmental stage of the leaves and their metabolic status. Plastidial phosphorylase (PHS1) and other enzymes play an essential role in this process since they are necessary for the synthesis of the substrates used by the initiation machinery. The mechanism of starch granule formation initiation in Arabidopsis seems to be generalizable to other plants and also to the synthesis of long-term storage starch. The latter, however, shows specific features due to the presence of more isoforms, the absence of constantly recurring starch synthesis and degradation, and the metabolic characteristics of the storage sink organs.
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