Early light-induced proteins protect Arabidopsis from photooxidative stress

Abstract

The early light-induced proteins (ELIPs) belong to the multigenic family of light-harvesting complexes, which bind chlorophyll and absorb solar energy in green plants. ELIPs accumulate transiently in plants exposed to high light intensities. By using an Arabidopsis thaliana mutant (chaos) affected in the posttranslational targeting of light-harvesting complex-type proteins to the thylakoids, we succeeded in suppressing the rapid accumulation of ELIPs during high-light stress, resulting in leaf bleaching and extensive photooxidative damage. Constitutive expression of ELIP genes in chaos before light stress resulted in ELIP accumulation and restored the phototolerance of the plants to the wild-type level. Free chlorophyll, a generator of singlet oxygen in the light, was detected by chlorophyll fluorescence lifetime measurements in chaos leaves before the symptoms of oxidative stress appeared. Our findings indicate that ELIPs fulfill a photoprotective function that could involve either the binding of chlorophylls released during turnover of pigment-binding proteins or the stabilization of the proper assembly of those proteins during high-light stress.L ight is essential for plants through photosynthetic carbon assimilation. However, when absorbed light exceeds the photosynthetic capacities, reactive O 2 species are generated in the chloroplasts, causing oxidative damage to proteins, lipids, and photosynthetic pigments (1, 2). This effect is amplified by environmental stresses such as low temperature or drought, for example, that inhibit the photosynthetic activity, leading to strong yield reduction in crops. In green plants, solar energy is collected by chlorophyll-and carotenoid-binding lightharvesting complexes (LHCs), which are encoded by a multigene family of LHC genes. The expression of these genes is tightly regulated by light (2-4). High light intensities inhibit transcription of LHC genes and activate synthesis of the early lightinduced proteins (ELIPs), a class of proteins structurally related to the LHCs (5). The ELIPs are predicted to have three transmembrane helices, and they have sequence similarity to the LHCs in the central pair of helices (6, 7). The similarity is not only at the sequence level, however, because both LHCs and ELIPs bind chlorophyll and carotenoids (8). The ELIPs differ from the LHCs by their transient expression under high-light stress (5). Recently, a number of ELIP-type polypeptides, containing LHC motifs and inducible by high light, have been discovered in vascular plants: the one-helix high-light-induced proteins (9) and the two-helix stress-enhanced proteins (10).The physiological role of the ELIPs in vascular plants has not yet been elucidated, although there have been several suggestions (11)(12)(13)(14). The induction of ELIPs by high light intensities suggests a role in the acclimation to light stress rather than a light-harvesting function, but this has not yet been demonstrated. ELIP antisense transgenic tobacco plants did not exhibit any phenotype of sensitivity to high ...

Expression of LHC Genes and their Relation to Photo-Oxidative Stress Tolerance Tolerance in Solanum lycopersicum L. and Solanum chilense (Dunal) Reiche

“…Thus, S. chilense seems to be more tolerant to oxidative stress, as indicated by their low levels of lipid peroxide. These results are in agreement with reports that less MDA formation is related to some mechanism of oxidative stress tolerance (Shalata and Neumann, 2001;Hutin et al, 2003;Golan et al, 2006).…”

“…However as shown in Figure 3B, there is an increase in zeaxanthin content, accordingly there are reports that indicate that zeaxanthin could be bound by other members of the LHC family, the ELIP proteins (Havaux et al, 2004;Demmig-Adams et al, 2006;Johnson et al, 2007). ELIP protein has been associated with photoprotection in tolerant species (Montané et al, 1999;Adamska, 2000;Hutin et al, 2003). An increase in ELIP transcript levels in S. chilense was expected, however no significant differences between both species was observed upon low temperature and high light treatment ( Figure 5B), suggesting, as in Hutin et al Changes in the xanthophyll cycle conversion state (a + z)/(v + a + z); B) changes in content of violaxanthin (v), anteraxanthin (a) and zeaxanthin (z) (c: control condition; s: stress condition).…”

“…It was proposed that PsbS, a distant member of the LHC family, might play a protective role within the thylakoids under photoinhibitory conditions, with a central role in NPQ (Li et al, 2000). A similar non-light harvesting function was proposed for ELIP proteins, another distant relative of LHC family that accumulates when the expression of Lhc proteins is downregulated and are therefore thought to play a role in photoprotection, either via a transient binding of free chlorophyll to avoid the transference to oxygen and/or in zeaxanthin-dependent photo-protection (Montané and Kloppstech, 2000;Adamska, 2000;Andersson et al, 2003;Hutin et al, 2003). Interestingly, the photosystem I (PSI) antenna complex is made up of proteins whose primary function is to collect energy.…”

Molecular mechanisms of desiccation tolerance in the resurrection glacial relic Haberlea rhodopensis

“…These genes were almost not expressed in well-watered and rehydrated plants, but their levels rise very sharply in plants experiencing drought and desiccation. Early lightinducible proteins are believed to associate with chlorophyll and prevent ROS-induced photooxidative damage [40].…”

Intraplastidial trafficking of a phage-type RNA polymerase is mediated by a thylakoid RING-H2 protein

“…Afterward, membrane proteins have been analyzed with antibodies made against RpL4, against the 33-kDa protein of the oxygen-evolving complex (OEC33; ref. 27), and against NIP. All three washing procedures detach RpL4 from the membranes, as expected for a protein that sticks nonspecifically to the thylakoids' stromal surface.…”