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Chromoplasts are colored plastids that synthesize and store massive amounts of carotenoids. Chromoplast number and size define the sink strength for carotenoid accumulation in plants. However, nothing is known about the mechanisms controlling chromoplast number. Previously, a natural allele of Orange (OR), ORHis, was found to promote carotenoid accumulation by activating chromoplast differentiation and increasing carotenoid biosynthesis, but cells in orange tissues in melon fruit and cauliflower OR mutant have only one or two enlarged chromoplasts. In this study, we investigated an ORHis variant of Arabidopsis OR, genetically mimicking the melon ORHis allele, and found that it also constrains chromoplast number in Arabidopsis calli. Both in vitro and in vivo experiments demonstrate that ORHis specifically interacts with the Membrane Occupation and Recognition Nexus domain of ACCUMULATION AND REPLICATION OF CHLOROPLASTS 3 (ARC3), a crucial regulator of chloroplast division. We further showed that ORHis interferes with the interaction between ARC3 and PARALOG OF ARC6 (PARC6), another key regulator of chloroplast division, suggesting a role of ORHis in competing with PARC6 for binding to ARC3 to restrict chromoplast number. Overexpression or knockout of ARC3 in Arabidopsis ORHis plants significantly alters total carotenoid levels. Moreover, overexpression of the plastid division factor PLASTID DIVISION 1 greatly enhances carotenoid accumulation. These division factors likely alter carotenoid levels via their influence on chromoplast number and/or size. Taken together, our findings provide novel mechanistic insights into the machinery controlling chromoplast number and highlight a potential new strategy for enhancing carotenoid accumulation and nutritional value in food crops.
Pubmed ID: 32222485
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Database of genetic and molecular biology data for the model higher plant Arabidopsis thaliana. Data available includes the complete genome sequence along with gene structure, gene product information, metabolism, gene expression, DNA and seed stocks, genome maps, genetic and physical markers, publications, and information about the Arabidopsis research community. Gene product function data is updated every two weeks from the latest published research literature and community data submissions. Gene structures are updated 1-2 times per year using computational and manual methods as well as community submissions of new and updated genes. TAIR also provides extensive linkouts from data pages to other Arabidopsis resources. The data can be searched, viewed and analyzed. Datasets can also be downloaded. Pages on news, job postings, conference announcements, Arabidopsis lab protocols, and useful links are provided.
View all literature mentionsThe mission of the Arabidopsis Biological Resource Center (ABRC) is to acquire, preserve and distribute seed and DNA resources that are useful to the Arabidopsis research community. More than 100,000 stocks are shipped annually to researchers in more than 60 countries, and modest fees for stocks are charged. The ABRC database functions and ordering system are incorporated into The Arabidopsis Information Resource (TAIR). Researchers can obtain information about Arabidopsis, perform stock searches, order stocks, and view current and past orders. Sponsors: ABRC is supported by the National Science Foundation under Grant No. 0542034.
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