The identification of the carotenoids in this study (Table 3; Fig. 2) and the completion of the entire nucleotide sequence of the genome in A. platensis NIES-39 (Fujisawa et al. 2010) will help facilitate the elucidation of the biosynthetic pathways and the corresponding enzymes and genes involved. Fig. 6 presents our proposed biosynthetic pathway of the carotenoids in A. platensis NIES-39. We have summarized the genes in A. platensis NIES-39 (Fujisawa et al. 2010) on the basis of sequence homology, in which only functionally confirmed genes were chosen for query sequences. This suggests the presence of CrtE, CrtB, CrtP, CrtQ, CrtH, CrtO and CruF (carotenoid 1,2-hydratase), in addition to functional CruA and CrtR (Table 4).
Table 4
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Candidates of other carotenoid biosynthesis genes in Arthrospira platensis NIES-39 based on carotenoids present

GeneEnzymeQuery sequence for BLASTPa,bAccession numberIdentity (%)/ e-value
CyanoBaseNCBI
crtEGeranylgeranyl diphosphate synthaseThermosynechococcus elongatus BP-1, tll0020NIES39_J00820BAI9113474/3e-162
crtBPhytoene synthaseSynechocystis sp. PCC 6803, slr1255NIES39_C00950BAI8896570/8e-156
crtPPhytoene desaturaseSynechocystis sp. PCC 6803, slr1254NIES39_C00940BAI8896480/0.0
crtQζ-Carotene desaturaseSynechocystis sp. PCC 6803, slr0940NIES39_B00980BAI8885575/0.0
crtHcis-Carotene isomeraseSynechocystis sp. PCC 6803, sll0033NIES39_C05040BAI8937076/0.0
cruALycopene cyclaseSynechococcus sp. PCC 7002, SYNPCC7002_A2153NIES39_A06350BAI8847365/0.0
cruPLycopene cyclaseSynechococcus sp. PCC 7002, SYNPCC7002_A0043NIES39_K00660BAI9171553/0.0
crtRβ-Carotene hydroxylaseSynechocystis sp. PCC 6803, sll1468NIES39_R00430BAI9435271/8e-165
crtOβ-Carotene ketolaseSynechocystis sp. PCC 6803, slr0088NIES39_L03850BAI9254224/2e-26
cruFCarotenoid 1,2-hydrataseSynechococcus sp. PCC 7002, SYNPCC7002_A2032NIES39_B01080BAI8886551/7e-88
GeneEnzymeQuery sequence for BLASTPa,bAccession numberIdentity (%)/ e-value
CyanoBaseNCBI
crtEGeranylgeranyl diphosphate synthaseThermosynechococcus elongatus BP-1, tll0020NIES39_J00820BAI9113474/3e-162
crtBPhytoene synthaseSynechocystis sp. PCC 6803, slr1255NIES39_C00950BAI8896570/8e-156
crtPPhytoene desaturaseSynechocystis sp. PCC 6803, slr1254NIES39_C00940BAI8896480/0.0
crtQζ-Carotene desaturaseSynechocystis sp. PCC 6803, slr0940NIES39_B00980BAI8885575/0.0
crtHcis-Carotene isomeraseSynechocystis sp. PCC 6803, sll0033NIES39_C05040BAI8937076/0.0
cruALycopene cyclaseSynechococcus sp. PCC 7002, SYNPCC7002_A2153NIES39_A06350BAI8847365/0.0
cruPLycopene cyclaseSynechococcus sp. PCC 7002, SYNPCC7002_A0043NIES39_K00660BAI9171553/0.0
crtRβ-Carotene hydroxylaseSynechocystis sp. PCC 6803, sll1468NIES39_R00430BAI9435271/8e-165
crtOβ-Carotene ketolaseSynechocystis sp. PCC 6803, slr0088NIES39_L03850BAI9254224/2e-26
cruFCarotenoid 1,2-hydrataseSynechococcus sp. PCC 7002, SYNPCC7002_A2032NIES39_B01080BAI8886551/7e-88

aTakaichi and Mochimaru (2007)

bMaresca et al. (2007)

Table 4
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Candidates of other carotenoid biosynthesis genes in Arthrospira platensis NIES-39 based on carotenoids present

GeneEnzymeQuery sequence for BLASTPa,bAccession numberIdentity (%)/ e-value
CyanoBaseNCBI
crtEGeranylgeranyl diphosphate synthaseThermosynechococcus elongatus BP-1, tll0020NIES39_J00820BAI9113474/3e-162
crtBPhytoene synthaseSynechocystis sp. PCC 6803, slr1255NIES39_C00950BAI8896570/8e-156
crtPPhytoene desaturaseSynechocystis sp. PCC 6803, slr1254NIES39_C00940BAI8896480/0.0
crtQζ-Carotene desaturaseSynechocystis sp. PCC 6803, slr0940NIES39_B00980BAI8885575/0.0
crtHcis-Carotene isomeraseSynechocystis sp. PCC 6803, sll0033NIES39_C05040BAI8937076/0.0
cruALycopene cyclaseSynechococcus sp. PCC 7002, SYNPCC7002_A2153NIES39_A06350BAI8847365/0.0
cruPLycopene cyclaseSynechococcus sp. PCC 7002, SYNPCC7002_A0043NIES39_K00660BAI9171553/0.0
crtRβ-Carotene hydroxylaseSynechocystis sp. PCC 6803, sll1468NIES39_R00430BAI9435271/8e-165
crtOβ-Carotene ketolaseSynechocystis sp. PCC 6803, slr0088NIES39_L03850BAI9254224/2e-26
cruFCarotenoid 1,2-hydrataseSynechococcus sp. PCC 7002, SYNPCC7002_A2032NIES39_B01080BAI8886551/7e-88
GeneEnzymeQuery sequence for BLASTPa,bAccession numberIdentity (%)/ e-value
CyanoBaseNCBI
crtEGeranylgeranyl diphosphate synthaseThermosynechococcus elongatus BP-1, tll0020NIES39_J00820BAI9113474/3e-162
crtBPhytoene synthaseSynechocystis sp. PCC 6803, slr1255NIES39_C00950BAI8896570/8e-156
crtPPhytoene desaturaseSynechocystis sp. PCC 6803, slr1254NIES39_C00940BAI8896480/0.0
crtQζ-Carotene desaturaseSynechocystis sp. PCC 6803, slr0940NIES39_B00980BAI8885575/0.0
crtHcis-Carotene isomeraseSynechocystis sp. PCC 6803, sll0033NIES39_C05040BAI8937076/0.0
cruALycopene cyclaseSynechococcus sp. PCC 7002, SYNPCC7002_A2153NIES39_A06350BAI8847365/0.0
cruPLycopene cyclaseSynechococcus sp. PCC 7002, SYNPCC7002_A0043NIES39_K00660BAI9171553/0.0
crtRβ-Carotene hydroxylaseSynechocystis sp. PCC 6803, sll1468NIES39_R00430BAI9435271/8e-165
crtOβ-Carotene ketolaseSynechocystis sp. PCC 6803, slr0088NIES39_L03850BAI9254224/2e-26
cruFCarotenoid 1,2-hydrataseSynechococcus sp. PCC 7002, SYNPCC7002_A2032NIES39_B01080BAI8886551/7e-88

aTakaichi and Mochimaru (2007)

bMaresca et al. (2007)

Proposed biosynthetic pathways of carotenoids and their enzymes in Arthrospira platensis NIES-39. CrtE, geranylgeranyl diphosphate synthase; CrtB, phytoene synthase; CrtP, phytoene desaturase; CrtQ, ζ-carotene desaturase; CrtH, cis-carotene isomerase; CruA, lycopene cyclase; CrtR, β-carotene hydroxylase; CrtO, β-carotene ketolase; CruF, carotenoid 1,2-hydratase.
Fig. 6

Proposed biosynthetic pathways of carotenoids and their enzymes in Arthrospira platensis NIES-39. CrtE, geranylgeranyl diphosphate synthase; CrtB, phytoene synthase; CrtP, phytoene desaturase; CrtQ, ζ-carotene desaturase; CrtH, cis-carotene isomerase; CruA, lycopene cyclase; CrtR, β-carotene hydroxylase; CrtO, β-carotene ketolase; CruF, carotenoid 1,2-hydratase.

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