AUTHOR=Lehmann Martin , Vamvaka Evgenia , Torrado Alejandro , Jahns Peter , Dann Marcel , Rosenhammer Lea , Aziba Amel , Leister Dario , Rühle Thilo 

TITLE=Introduction of the Carotenoid Biosynthesis α-Branch Into Synechocystis sp. PCC 6803 for Lutein Production

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.699424

DOI=10.3389/fpls.2021.699424

ISSN=1664-462X

ABSTRACT=<p>Lutein, made by the α-branch of the methyl-erythritol phosphate (MEP) pathway, is one of the most abundant xanthophylls in plants. It is involved in the structural stabilization of light-harvesting complexes, transfer of excitation energy to chlorophylls and photoprotection. In contrast, lutein and the α-branch of the MEP pathway are not present in cyanobacteria. In this study, we genetically engineered the cyanobacterium <italic>Synechocystis</italic> for the missing MEP α-branch resulting in lutein accumulation. A cassette comprising four <italic>Arabidopsis thaliana</italic> genes coding for two lycopene cyclases (<italic>AtLCYe</italic> and <italic>AtLCYb</italic>) and two hydroxylases (<italic>AtCYP97A</italic> and <italic>AtCYP97C</italic>) was introduced into a <italic>Synechocystis</italic> strain that lacks the endogenous, cyanobacterial lycopene cyclase <italic>cruA</italic>. The resulting <italic>synlut</italic> strain showed wild-type growth and only moderate changes in total pigment composition under mixotrophic conditions, indicating that the <italic>cruA</italic> deficiency can be complemented by <italic>Arabidopsis</italic> lycopene cyclases leaving the endogenous β-branch intact. A combination of liquid chromatography, UV-Vis detection and mass spectrometry confirmed a low but distinct synthesis of lutein at rates of 4.8 ± 1.5 nmol per liter culture at OD<sub>730</sub> (1.03 ± 0.47 mmol mol<sup>–1</sup> chlorophyll). In conclusion, <italic>synlut</italic> provides a suitable platform to study the α-branch of the plastidic MEP pathway and other functions related to lutein in a cyanobacterial host system.</p>