Composition and function of plastoglobuli

Abstract

The lipid composition of whole leaves and isolated plastoglobul of beech (Fagus sylvatica) has been studied during four natural autumnal senescence stages. Chlorophylls, glycolipids, and phospholipids were extensively degraded in leaves. About 20% of the glycolipids found in leaves during summer, however, remained in the last stage of leaf senescence. Triacylglycerols, also detected in large amounts in summer leaves, were hydrolyzed during senescence. The content of free fatty acids derived from degradation of glycerolipids therefore increased. The total carotenoid and prenyl quinone content was largely unchanged during senescence, except during the last stage investigated, but the reduced forms of prenyl quinones decreased while the oxidized prenyl quinones increased. Plastoglobuli isolated from summer leaves mainly contained triacylglycerols, plastohydroquinone, and α-tocopherol. The triacylglycerol content declined in plastoglobuli during senescence. Most of the triacylglycerols must be located outside the plastoglobuli throughout the stages investigated. Carotenoids liberated from thylakoids were esterified and increasingly deposited in plastoglobuli during senescence. In the last senescence stage, carotenoid esters were the main component of plastoglobuli. Prenyl quinones were also transferred into plastoglobuli. Reduced prenyl quinones were sucessively oxidized during senescence and plastoquinone (oxidized) was the predominant prenyl quinone in plastoglobuli isolated from the last senescence stage. The carotenoid and prenyl quinone distribution was identical in leaves and plastoglobuli during late senescence. The main constituents of thylakoids, glycolipids and proteins, were not deposited in plastoglobuli and therefore did not play an important role in plastoglobuli metabolism.

Deficiency in Phylloquinone (Vitamin K1) Methylation Affects Prenyl Quinone Distribution, Photosystem I Abundance, and Anthocyanin Accumulation in the Arabidopsis AtmenG Mutant

“…60 and 30% of total phylloquinone (Fig. 4), respectively, confirming previous data on the identification of phylloquinone in plastoglobules (45). Therefore, the excess amount of phylloquinone not associated with PSI localizes to the plastoglobules of chloroplasts.…”

Tocopherol Cyclase (VTE1) Localization and Vitamin E Accumulation in Chloroplast Plastoglobule Lipoprotein Particles

“…Plastoglobules may, therefore, not only be the site of the tocopherol cyclase but may also be involved in the trafficking of tocopherol biosynthetic intermediates. The presence of tocopherol cyclase in the plastoglobule fraction is consistent with the reported presence of tocopherols in plastoglobules (11,13,15). In Arabidopsis plastoglobules, tocopherols are highly enriched with regard to total fatty acid content (Fig.…”

“…Indeed, plastoglobules enlarge during thylakoid disassembly in senescing chloroplasts and during chromoplast differentiation (4 -10) and increasingly accumulate triacylglycerols and esterified isoprenoids derived from the disintegrating thylakoids (6, 11). Plastoglobules have been reported to contain prenylquinones tocopherol and plastoquinone (8,(11)(12)(13)(14)(15), but the relative abundance of these compounds with regard to other chloroplast compartments is unknown. Although tocopherols are thought to function as antioxidants mostly at the thylakoid membrane, most of the prenylquinone biosynthetic activities have been localized to the inner chloroplast envelope membrane (16 -18).…”

Structural and ultrastructural study of Capsicum annuum leaves after treatment with Uncaria tomentosa bark extracts

“…It has been long known that plastoglobuli are the site of deposition of estrified carothenoids (Lichtehnthaler 1969). Also Tevini and Steinmuller (1985) have reported on an increased level of estrified carothenoids in plastoglobuli of ageing beech leaves. We might as well speculate that some lipid soluble 202 Tykarska T. et al…”

“…Along with the afore-described phenomena, processes typical of ageing occur in the oldest examined leaves (Barton 1966;Tevini and Steinmuller 1985;Nii et al 1988). They include changes in chloroplasts (increase in size of vacuoles and change in their color, dilatation of thylakoids, lower amount of starch), condensation of nuclear chromatin, condensation of mitochondrial matrix.…”