Journal
PLANT JOURNAL
Volume 80, Issue 3, Pages 410-423Publisher
WILEY
DOI: 10.1111/tpj.12637
Keywords
GFS9; transparent testa; flavonoid; vesicle trafficking; vacuole; Golgi apparatus; Arabidopsis thaliana
Categories
Funding
- Japan Society for the Promotion of Science (JSPS) [22000014, 21200065, 25440132, 231092]
- Ministry of Education, Culture, Sports, Science, and Technology (MEXT) of Japan
- Grants-in-Aid for Scientific Research [25440132, 21200065, 22000014, 25650096] Funding Source: KAKEN
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Flavonoids are the most important pigments for the coloration of flowers and seeds. In plant cells, flavonoids are synthesized by a multi-enzyme complex located on the cytosolic surface of the endoplasmic reticulum, and they accumulate in vacuoles. Two non-exclusive pathways have been proposed to mediate flavonoid transport to vacuoles: the membrane transporter-mediated pathway and the vesicle trafficking-mediated pathway. No molecules involved in the vesicle trafficking-mediated pathway have been identified, however. Here, we show that a membrane trafficking factor, GFS9, has a role in flavonoid accumulation in the vacuole. We screened a library of Arabidopsis thaliana mutants with defects in vesicle trafficking, and isolated the gfs9 mutant with abnormal pale tan-colored seeds caused by low flavonoid accumulation levels. gfs9 is allelic to the unidentified transparent testa mutant tt9. The responsible gene for these phenotypes encodes a previously uncharacterized protein containing a region that is conserved among eukaryotes. GFS9 is a peripheral membrane protein localized at the Golgi apparatus. GFS9 deficiency causes several membrane trafficking defects, including the mis-sorting of vacuolar proteins, vacuole fragmentation, the aggregation of enlarged vesicles, and the proliferation of autophagosome-like structures. These results suggest that GFS9 is required for vacuolar development through membrane fusion at vacuoles. Our findings introduce a concept that plants use GFS9-mediated membrane trafficking machinery for delivery of not only proteins but also phytochemicals, such as flavonoids, to vacuoles.
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