Xanthophyll cycle pigment localization and dynamics during exposure to low temperatures and light stress in vinca major

Abstract

The distribution of xanthophyll cycle pigments (violaxanthin plus antheraxanthin plus zeaxanthin [VAZ]) among photosynthetic pigment-protein complexes was examined in Vinca major before, during, and subsequent to a photoinhibitory treatment at low temperature. Four pigment-protein complexes were isolated: the core of photosystem (PS) II, the major light-harvesting complex (LHC) protein of PSII (LHCII), the minor light-harvesting proteins (CPs) of PSII (CP29, CP26, and CP24), and PSI with its LHC proteins (PSI-LHCI). In isolated thylakoids 80% of VAZ was bound to protein independently of the de-epoxidation state and was found in all complexes. Plants grown outside in natural sunlight had higher levels of VAZ (expressed per chlorophyll), compared with plants grown in low light in the laboratory, and the additional VAZ was mainly bound to the major LHCII complex, apparently in an acid-labile site. The extent of de-epoxidation of VAZ in high light and the rate of reconversion of Z plus A to V following 2.5 h of recovery were greatest in the free-pigment fraction and varied among the pigment-protein complexes. Photoinhibition caused increases in VAZ, particularly in low-light-acclimated leaves. The data suggest that the photoinhibitory treatment caused an enrichment in VAZ bound to the minor CPs caused by de novo synthesis of the pigments and/or a redistribution of VAZ from the major LHCII complex.

Figure 1

Fully denaturing Tris-sulfate SDS-PAGE of the fractions obtained from Suc-gradient ultracentrifugation of V. major thylakoids collected from dark-adapted (at least 12 h) leaves of GC plants. Fractions from stressed and recovered thylakoids, as well as the fractions obtained from plants grown OD, were very similar and are therefore not depicted. Whole thylakoids (T) were loaded onto the gel in addition to the four fractions (F2–F5) collected; fraction 2 contained the LHCII monomer (B), the minor Chl proteins CP29 (A), CP26 (comigrating with LHCII; B), and CP24 (C); fraction 3 contained the LHCII trimer (D); fraction 4 contained the PSII core with the D1/D2 heterodimer (E), CP47 (F), CP43 (G), and D1/D2 monomer (H); fraction 5 contained the PSI core (I) and LHCI (J). Fraction 1 contained the free pigments (Table III) and is not depicted here.

Figure 2

Fully denaturing Tris-Tricine SDS-PAGE of the bands (bands 1–8) collected following glycerol gradients of IEF fractions from separation of LHCII monomer and the minor Chl proteins of samples obtained from V. major plants grown OD. The three gels depict samples from the control, stress, and recovery sets of experiments, as indicated. Thylakoids were loaded as a standard (CT, ST, and RT). CP29 (A), CP26 (B), LHCII (C), and CP24 (D) are indicated.

Figure 3

A, Densitometric analysis of Coomassie Blue-stained gels of bands from nondenaturing green gels of the minor CPs and LHCII monomer from samples obtained from plants grown OD (two bands were apparent in each lane). A, Relative percentages of CP29, LHCII, and CP26 in each band. B, The contents of the xanthophyll cycle pigments analyzed for each band.