Disease relevance of Phytoene

• Cells of Escherichia coli that expressed the tomato pds gene could convert phytoene to zeta-carotene [1].
• A cDNA encoding phytoene synthase and a partial cDNA encoding phytoene desaturase (PDS) were placed under the transcriptional control of a tobamovirus subgenomic promoter [2].
• The deduced amino acid sequences of the phytoene desaturases from other microorganisms (purple bacteria and fungi) appear to be evolutionarily unrelated to those from green photosynthetic organisms [1].
• The lycopene cyclase domain of carRA derived from a duplication of a gene from a common ancestor of fungi and Brevibacterium linens; the phytoene synthase domain is similar to the phytoene and squalene synthases of many organisms; but the regulatory functions appear to be specific to Phycomyces [3].
• Expression in Escherichia coli, purification, and reactivation of the recombinant Erwinia uredovora phytoene desaturase [4].

High impact information on Phytoene

• We investigated the effects of human selection for yellow endosperm color, representing increased carotenoid content, on two maize genes, the Y1 phytoene synthase and PSY2, a putative second phytoene synthase [5].
• Contrasting effects of selection on sequence diversity and linkage disequilibrium at two phytoene synthase loci [5].
• The albino sectors of im plants contain reduced levels of carotenoids and increased levels of the carotenoid precursor phytoene [6].
• Here, we report the identification and characterization of two nonallelic albino mutations, pds1 and pds2 (for phytoene desaturation), that are disrupted in phytoene desaturation and as a result accumulate phytoene, the first C40 compound of the pathway [7].
• More recently, breeders have selected yellow endosperm variants of maize over ancestral white phenotypes for their increased nutritional value resulting from the up-regulation of the Y1 phytoene synthase gene product in endosperm tissue [8].

Chemical compound and disease context of Phytoene

• Molecular and biochemical characterization of herbicide-resistant mutants of cyanobacteria reveals that phytoene desaturation is a rate-limiting step in carotenoid biosynthesis [9].
• Replacing the native 3-step phytoene desaturase (CrtI) with the 4-step enzyme from Erwinia herbicola results in significant flux down the spirilloxanthin pathway for the first time in Rb. sphaeroides [10].
• On the other hand, phytoene, canthaxanthin, beta-cryptoxanthin and zeaxanthin did not affect the growth of the prostate cancer cells [11].
• In contrast, a strain of E. coli carrying geranylgeranyl diphosphate synthase, phytoene desaturase and the bacterial carotene desaturase CrtI, which mediates lycopene formation from phytoene, does not require light, nor is a poly-cis-lycopene species formed [12].
• We previously demonstrated the production of beta-carotene in Rhodovulum sulfidophilum by cloning the Erythrobacter longus crtI (phytoene dehydrogenase) and crtY (lycopene cyclase) genes [13].

Biological context of Phytoene

• The leaves of the plants transfected with the antisense PDS sequence developed a white phenotype and also accumulated high levels of phytoene [2].
• Es. coli JM101 was transformed with the expression plasmid, and transformants were assayed for GGPP synthase and phytoene synthase activity [14].
• CarQ, a proposed extracytoplasmic (ECF) RNA polymerase sigma factor, is required for expression of the operon and the carC gene that encodes phytoene dehydrogenase [15].
• Nucleotide sequence of an Arabidopsis cDNA for phytoene synthase [16].
• A cDNA coding for the carotenoid biosynthetic enzyme phytoene synthase was cloned from a Narcissus pseudonarcissus flower cDNA library, and the corresponding protein was overexpressed in insect cells using the baculovirus lipofection system [17].

Anatomical context of Phytoene

• Fruit-specific expression was achieved by using the tomato polygalacturonase promoter, and the CRTB protein was targeted to the chromoplast by the tomato phytoene synthase-1 transit sequence [18].
• Once bound to membranes, activated phytoene desaturase works independently of any added FAD, employing membrane-bound electron acceptors [19].
• Cells cultured in the biphasic system were viable and able to produce phytoene during 3 days [20].
• METHODS: Normal human dermal fibroblast cell cultures were exposed to either 50 mJ of UVR or to IL-1 and then incubated with various concentrations of either CoQ10, the colorless carotenoids, phytoene and phytofluene, or to combinations of these antioxidants [21].

Associations of Phytoene with other chemical compounds

• Analysis of pds1 and pds2 shows that both mutants are plastoquinone and tocopherol deficient, in addition to their inability to desaturate phytoene [7].
• Dissociation of prelycopersene pyrophosphate synthetase from phytoene synthetase complex of tomato fruit plastids [22].
• Using different isoprenoid biosynthetic gene probes from cloned cDNAs, we showed that only genes encoding the plastid enzymes (geranylgeranyl pyrophosphate synthase, phytoene synthase, phytoene desaturase, and capasanthin-capsorubin synthase) are specifically triggered during the normal period of development, at the ripening stage [23].
• Barley infected with BSMV expressing barley, rice or maize PDS fragments became photo-bleached and accumulated phytoene (the substrate for PDS) in a manner similar to plants treated with the chemical inhibitor of PDS, norflurazon [24].
• For tumors induced by DMBA/croton oil or DMBA/UV-B, mice receiving beta-carotene showed a significant difference in tumor numbers and appearance time from placebo mice; phytoene and canthaxanthin treatment had no effect [25].

Gene context of Phytoene

• Previous analyses of phytoene-accumulating tissue suggested that there may be feedback regulation of PDS gene transcription, with higher expression in white tissue [26].
• In this report, we have located the transcription initiation point and have shown that R. sphaeroides possesses an oxygen-regulated CrtI-type phytoene desaturase gene that forms a transcriptional operon with crtB [27].
• Analysis of the sequence of the Synechocystis pys protein deduced from the gene sequence shows that it is highly homologous to the tomato and Synechococcus phytoene synthases and shows conserved domains with other bacterial phytoene synthase enzymes [28].
• The enzyme phytoene synthase (Psy) catalyzes the formation of phytoene, an intermediate in the carotenoid biosynthesis pathway [29].
• In contrast, barley infected with wild-type BSMV, or BSMV expressing either N. benthamiana PDS or antisense green fluorescent protein (GFP), did not photo-bleach or accumulate phytoene [24].

Analytical, diagnostic and therapeutic context of Phytoene

• High-performance liquid chromatography and infrared analysis showed that phytoene adopted the 15-cis and all-trans forms (as in higher plants), and that lycopene primarily adopted the all-trans form [30].
• By immunoprecipitations we have shown that the plastid Hsp70 is a structural constituent of a soluble entity also containing phytoene desaturase [31].
• Genetic crosses and recombination tests revealed that all individual white mutants in the collection are alleles of a single gene, lts1, and the white phenotype was closely linked to a marker located in the phytoene synthase gene [32].
• Bacterial phytoene synthase: molecular cloning, expression, and characterization of Erwinia herbicola phytoene synthase [33].
• These data were supported by the detection of phytoene synthase protein on western blots [34].

References