Proteomics, pigment composition, and organization of thylakoid membranes in iron-deficient spinach leaves

Abstract

The changes induced in the photosynthetic apparatus of spinach (Spinacia oleracea L.) seedlings exposed to iron deficiency shortly after germination were characterized with two proteomic approaches coupled with chlorophyll and xanthophyll analysis and in vivo measurements of photosynthesis. During the first 10 d of iron deficiency the concentrations of chlorophyll b and violaxanthin were greatly reduced, but all xanthophylls recovered after 13-17 d of iron deficiency, when both chlorophylls were negatively affected. No new protein was formed in iron-deficient leaves, and no protein disappeared altogether. Photosystem I (PSI) proteins were largely reduced, but the stoichiometry of the antenna composition of PSI was not compromised. On the contrary, PSII proteins were less affected by the stress, but the specific antennae Lhcb4 and Lhcb6, Lhcb2 and its isoform Lhcb1.1 were all reduced, while the concentration of Lhcb3 increased. A strong reduction in thylakoid bending and an altered distribution pattern for the reduced PSI and PSII complexes were observed microscopically in iron-deficient leaves. Supercomplex organization was also affected by the stress. The trimeric organization of Lhcb and the dimerization of Lhca were reduced, while monomerization of Lhcb increased. However, the trimerization of Lhcb was partially recovered after 13-17 d of iron deficiency. In iron-deficient leaves, photosynthesis was strongly inhibited at different light intensities, and a high de-epoxidation status of the xanthophylls was observed, in association with a strong impairment of photochemical efficiency and an increase of heat dissipation as monitored by the non-photochemical quenching of fluorescence. All these negative effects of iron deficiency were attenuated but not fully reversed after again supplying iron to iron-deficient leaves for 7-13 d. These results indicate that iron deficiency has a strong impact on the proteomic structure of spinach photosystems and suggest that, in higher plants, adaptive mechanisms common in lower organisms, which allow rapid changes of the photosystem structure to cope with iron stress, are absent. It is speculated that the observed changes in the monomer-trimer equilibrium of major PSII antennae, which is possibly the result of xanthophyll fluctuations, is a first adaptative adjustment to iron deficiency, and may eventually play a role in light dissipation mechanisms.

A Program for Iron Economy during Deficiency Targets Specific Fe Proteins

“…It is of interest to place our findings in the context of studies that have reported on the general effects of Fe deficiency on chlorophyll synthesis and photosynthesis that have been well documented in the literature (Spiller and Terry, 1980;Andaluz et al, 2006;Nishio and Terry, 1983;Nishio et al, 1985;Sharma, 2007;Timperio et al, 2007;Laganowski et al, 2009;Msilini et al, 2011;Ciaffi et al, 2013;Paolacci et al, 2014;Rodríguez-Celma et al, 2013). Some studies on Fe depletion in plants reported that PSI was the major target of Fe deficiency (Nishio et al, 1985;Timperio et al, 2007), whereas we saw a major effect on the cytochromeb 6 f complex and less on PSI.…”

“…Some studies on Fe depletion in plants reported that PSI was the major target of Fe deficiency (Nishio et al, 1985;Timperio et al, 2007), whereas we saw a major effect on the cytochromeb 6 f complex and less on PSI. The severity of the applied Fe deficiency, differences in light conditions, and the use of different species may all help determine if PSI or the cytochrome-b 6 f complex is more affected.…”

Development and recovery of iron deficiency by iron resupply to roots or leaves of strawberry plants

“…For example, Fe resupply leads to increases in Chl concentration and photosynthetic rate [15,16] and decreases in the concentration of organic acids [4,17]. Additionally, the reduction of the carboxylate concentration in xylem sap and in leaf apoplast was also reported in sugar beet [18] and fruit trees [19].…”

“…In a recent review paper, [1] stated that studies involving the responses of Fe-deficient plants resupplied with Fe are still scarce and may provide crucial [15] information for the optimization of the Fe-fertilization strategies. The aims of the present study were to characterize the changes induced by Fe depletion on the Chl content, root FC-R and mineral composition of roots and leaves and to compare two different ways to resupply Fe: by foliar or root fertilization.…”

Thylakoidal Pigment-Protein Complexes: Critical Requirement of Sulphur for Proper Assemblage and Photosynthesis in Arabidopsis thaliana

“…thaliana leaves were washed with cold water and used for extraction of thylakoid membranes as described by Timperio et al [9] and processed as described by D' Amici et al [10]. BN-SDS-PAGE, image analysis, tryptic digestion of proteins, peptide sequencing and identification was done as described previously [6].…”