Journal
JOURNAL OF CEREAL SCIENCE
Volume 101, Issue -, Pages -Publisher
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jcs.2021.103317
Keywords
OsGUN4; Starch biosynthesis; Rice; Heme; Grain development
Categories
Funding
- Natural Foundation of Anhui Province [1908085QC103]
- Open Project Program of State Key Laboratory of Rice Biology [20200104]
- Anhui Agricultural University [yj 2018-39]
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The study revealed that OsGUN4 is expressed both in leaves and developing seeds, and its mutation affects sucrose accumulation and transportation in leaves, as well as starch biosynthesis in developing grains. OsGUN4 plays a potential role in mediating starch biosynthesis through tetrapyrrole metabolites during early seed development.
Seed formation requires the supply of sucrose derived from leaves and the functioning of starch biosynthetic enzymes during seed development, of which are related to the tetrapyrrole metabolism. Here, we found that, aside from leaves, the Genome Uncoupled 4 (OsGUN4) was also predominantly expressed at 7-14 days after flowering (DAF) in developing seeds, whereas its down-regulation produced aberrant grain appearances and altered storage substances in the epi-genetic mutant of gun4epi seeds, which was attributed to abnormal performance of metabolites and starch biosynthetic enzymes. Moreover, the OsGUN4 mutation would greatly affect the sucrose accumulation in leaves and the sucrose transportation in phloem, which was related to the weak photosynthesis resulted from reduced chlorophylls. Conversely, in developing grains, the OsGUN4 mutation led to the accumulation of sucrose and the tetrapyrrole metabolites, i.e., protoporphyrin IX (PPIX) and heme, but inhibited synthesis of storage starch. Additionally, feeding of the exogenous heme also greatly suppressed the expression of starch biosynthetic genes at 7 to 14 DAF in developing grains, suggesting its similar effects to the OsGUN4 mutation during starch biosynthesis. Collectively, these findings demonstrated that OsGUN4 was a potential regulator to mediate starch biosynthesis via tetrapyrrole metabolites early during seed development.
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