FIGURE 7.

Loss of eIFiso4G expression results in an increase in VDE expression and de-epoxidation. A, the xanthophyll cycle. NPQ1 encodes violaxanthin de-epoxidase (VDE) whereas NPQ2 encodes ZE. B, xanthophyll pigments were isolated from leaves of plants grown at 100 PFD that were either dark-adapted for 16 h, maintained under 100 PFD, or exposed to 600 PFD for 60 min. Xanthophyll pigments were quantitated by HPLC and normalized to chlorophyll a. The de-epoxidation status, i.e. (A + Z)/(V + A + Z), was determined from the amounts of V, A, and Z and is included below each pie chart. C, VDE relative to normalized RbcL protein levels were measured by Western analysis in adult leaves of the mutants indicated. D and E, VDE (D) and ZE enzyme (E) activities were measured in adult leaves of the mutants indicated.