TY - JOUR

T1 - Starch phosphorylation regulates starch granule morphological homogeneity in Arabidopsis thaliana

AU - Li, Xiaoping

AU - Ahmad, Abubakar Musa

AU - Zhong, Yuyue

AU - Ding, Li

AU - Blennow, Andreas

AU - Fettke, Joerg

N1 - © The Author(s) 2023. Published by Oxford University Press on behalf of American Society of Plant Biologists.

PY - 2024

Y1 - 2024

N2 - Starch granule morphological homogeneity presents a gap in starch research. Transitory starch granules in wild-type plants are discoid, regardless of species. Notably, while the shape of starch granules can differ among mutants, it typically remains homogeneous within a genotype. We found an Arabidopsis thaliana mutant, dpe2sex4, lacking both the cytosolic disproportionating enzyme (DPE2) and glucan phosphatase SEX4, showing an unprecedented bimodal starch granule diameter distribution when grown under a light/dark rhythm. dpe2sex4 contained two types of starch granules: large granules and small granules. In contrast to the double starch initiation in wheat (Triticum aestivum) endosperm, where A-type granules are initiated first and B-type granules are initiated later, dpe2sex4 small and large granules developed simultaneously in the same chloroplast. Compared with the large granules, the small granules had more branched amylopectin and less surface starch-phosphate, thus having a more compact structure which may hinder starch synthesis. During plant aging, the small granules barely grew. In in vitro experiments, fewer glucosyl residues were incorporated in small granules. Under continuous light, dpe2sex4 starch granules were morphologically homogeneous. Omitting the dark phase after a two-week light/dark cycle by moving plants into continuous light also reduced morphological variance between these two types of granules. These data shed light on the impact of starch phosphorylation on starch granule morphology homogeneity.

AB - Starch granule morphological homogeneity presents a gap in starch research. Transitory starch granules in wild-type plants are discoid, regardless of species. Notably, while the shape of starch granules can differ among mutants, it typically remains homogeneous within a genotype. We found an Arabidopsis thaliana mutant, dpe2sex4, lacking both the cytosolic disproportionating enzyme (DPE2) and glucan phosphatase SEX4, showing an unprecedented bimodal starch granule diameter distribution when grown under a light/dark rhythm. dpe2sex4 contained two types of starch granules: large granules and small granules. In contrast to the double starch initiation in wheat (Triticum aestivum) endosperm, where A-type granules are initiated first and B-type granules are initiated later, dpe2sex4 small and large granules developed simultaneously in the same chloroplast. Compared with the large granules, the small granules had more branched amylopectin and less surface starch-phosphate, thus having a more compact structure which may hinder starch synthesis. During plant aging, the small granules barely grew. In in vitro experiments, fewer glucosyl residues were incorporated in small granules. Under continuous light, dpe2sex4 starch granules were morphologically homogeneous. Omitting the dark phase after a two-week light/dark cycle by moving plants into continuous light also reduced morphological variance between these two types of granules. These data shed light on the impact of starch phosphorylation on starch granule morphology homogeneity.

U2 - 10.1093/plphys/kiad656

DO - 10.1093/plphys/kiad656

M3 - Journal article

C2 - 38060678

VL - 194

SP - 2600

EP - 2615

JO - Plant Physiology

JF - Plant Physiology

SN - 0032-0889

IS - 4

ER -