High impact information on LUT2

• Surprisingly, despite the absence of lutein, neither the lut1 nor lut2 mutation causes a visible deleterious phenotype or altered chlorophyll content, but both mutants have significantly higher levels of beta, beta-carotenoids [1].
• The lut2 mutations are semidominant, and their biochemical phenotype is consistent with a disruption of epsilon ring cyclization [1].
• We reported earlier that the Arabidopsis thaliana lycopene epsilon-cyclase (LCYe) adds one epsilon-ring to the symmetrical linear substrate lycopene, whereas the structurally related lycopene beta-cyclase (LCYb) adds two beta-rings [2].
• In lut2, lutein is replaced mainly by a stoichiometric increase in violaxanthin and antheraxanthin [3].
• Zeaxanthin functioned in vivo as a light-harvesting accessory pigment in lut2 npq2 chlorophyll antennae [4].

Biological context of LUT2

• While PSII photoinhibition was similar in wild type and lut2 npq2 exposed to high light at low temperature, the double mutant was much more resistant to photooxidative stress and lipid peroxidation than the wild type [4].
• The active xanthophyll cycle pool in lut2 exhibited a lower ( approximately 35% of WT) concentration efficiency, for a given intrathylakoid pH, to increase the sub-nanosecond distribution amplitudes, which predicts and explains inhibited induction kinetics and fluorescence quenching [5].

Associations of LUT2 with chemical compounds

• Regulation of carotenoid biosynthesis during tomato fruit development: expression of the gene for lycopene epsilon-cyclase is down-regulated during ripening and is elevated in the mutant Delta [6].
• The cDNA for lycopene epsilon-cyclase (CrtL-e), which converts lycopene to delta-carotene, was cloned from tomato [6].
• The lut2 exhibited separate active and inactive pools of antheraxanthin and zeaxanthin with respect to all deepoxidation, epoxidation and fluorescence quenching activities [5].
• A second single mutant (lut2) inhibits the in-cyclization enzyme step between lycopene and beta,in-carotene causing accumulation of beta,beta-carotene derivatives, primarily the violaxanthin cycle pigments, at the expense of lutein [5].

References