"Phytoene synthase catalyzes the dimerization of two molecules of geranylgeranyl pyrophosphate to phytoene and has been shown to be rate limiting for the synthesis of carotenoids."

"In the present paper, we show that seed-specific overexpression of an endogenous Arabidopsis phytoene synthase gene results in significant increases of the levels of β-carotene, luteins, and violaxanthin."

"An endogenous phytoene synthase was sequenced and cloned by RT-PCR from Arabidopsis homologous to the gene cloned by Scolnik and Bartley ( 1994 )."

"which unambiguously identified 1325 proteins"

"Arabidopsis has only one At-PSY."

"These PSYs localized to chloroplasts in specific fixed speckles, distributed inside the plastid and attached to areas that displayed red chlorophyll fluorescence indicative of prolamellar bodies or thylakoids."

"Merging of both signals confirmed colocalization of PSYs with Zm-PG2; thus, we consider the speckles to be plastoglobuli."

"Arabidopsis PSY localized to plastoglobules (as did maize PSY2 and 3 and rice PSY1, 2, and 3)."

"Chloroplast suborganellar localization of the key pathway enzyme, PSY , has yet to be detected by proteomic analysis."

"Phytoene synthase (PSY) catalyzes the first committed step in carotenoid biosynthesis and controls carbon flux into the carotenoid biosynthetic pathway"

"Among these proteins, PSY was the only one exclusively localized in chloroplasts as shown in a previous report ( 27 ) and the current study ( SI Appendix , Fig. S1 )."

"Both Arabidopsis OR proteins interacted directly with PSY ( Fig. 1 A )."

"PSY activity was about 50% higher in the AtOR -overexpressing lines than in WT."

"Overexpression of PSY – GFP led to about a twofold increase of phytoene in NFZ-treated etiolated seedlings ( Fig. 4 C ), indicating that PSY – GFP functioned properly in the transgenic lines."

"Here PSY activity was exclusively found membrane bound and required addition of active GGPP synthase for in vitro assay."

"Although the OR proteins carry a DnaJ cysteine-rich zinc figure domain, they are not molecular chaperones due to the lack of the DnaJ-like defining J domain."

"The results indicated that AtOR and AtOR-like were sufficient and required to regulate PSY protein levels in vivo, and that AtOR and AtOR-like were functionally redundant."

"The first committed step in the carotenoid biosynthesis pathway is the condensation of two geranylgeranyl diphosphate molecules to phytoene catalyzed by phytoene synthase (PSY)."

"Such interactions occurred in chloroplasts, consistent with the plastidial localizations of these proteins"

"Arabidopsis FBN6 was found to be among the proteins co-immunoprecipitated with a GFP-tagged version of phytoene synthase (PSY), the first and main rate-determining enzyme of the carotenoid pathway (Welsch et al. 2018)."

"FBN6 is the only FBN enriched in purified envelope fractions where PSY is also found (Ferro et al. 2010; Bouchnak et al. 2019)."

"When analyzing the co-immunoprecipitation assays, we noticed that the PSY-GFP protein concentrated in fluorescent dots within chloroplasts (Fig. 2A)."

"indicating that FBN6 and PSY co-localize within chloroplasts, as expected for interacting proteins."

"Strains co-transformed with such constructs harboring Arabidopsis PSY and FBN6 sequences were found to produce significantly more β-carotene than those expressing only PSY or co-expressing PSY and FBN4 (Fig. 3, B and C), despite that PSY protein levels remained very similar in all the cases (Fig. 3D)."

"While phytoene was not detected in control or FBN6 samples, it was present in PSY samples, and it increased in samples agroinfiltrated with both FBN6 and PSY (Fig. 4A)."

"our data support the conclusion that FBN6 plays a physiologically relevant role in carotenoid biosynthesis in Arabidopsis chloroplasts by physically binding to PSY to promote its enzymatic activity."

"Xref=Rhea:RHEA:34475, ChEBI:CHEBI:27787,"

"SUBCELLULAR LOCATION: Plastid, chloroplast membrane"

"/note="Chloroplast""