Excess manganese differentially inhibits photosystem I versus II inArabidopsis thaliana

Abstract

The effects of exposure to increasing manganese concentrations (50–1500 µM) from the start of the experiment on the functional performance of photosystem II (PSII) and photosystem I (PSI) and photosynthetic apparatus composition of Arabidopsis thaliana were compared. In agreement with earlier studies, excess Mn caused minimal changes in the PSII photochemical efficiency measured as Fv/Fm, although the characteristic peak temperature of the S2/3QB – charge recombinations was shifted to lower temperatures at the highest Mn concentration. SDS-PAGE and immunoblot analyses also did not exhibit any significant change in the relative abundance of PSII-associated polypeptides: PSII reaction centre protein D1, Lhcb1 (major light-harvesting protein of LHCII complex), and PsbO (OEC33, a 33kDa protein of the oxygen-evolving complex). In addition, the abundance of Rubisco also did not change with Mn treatments. However, plants grown under excess Mn exhibited increased susceptibility to PSII photoinhibition. In contrast, in vivo measurements of the redox transients of PSI reaction centre (P700) showed a considerable gradual decrease in the extent of P700 photooxidation (P700+) under increased Mn concentrations compared to control. This was accompanied by a slower rate of P700+ re-reduction indicating a downregulation of the PSI-dependent cyclic electron flow. The abundance of PSI reaction centre polypeptides (PsaA and PsaB) in plants under the highest Mn concentration was also significantly lower compared to the control. The results demonstrate for the first time that PSI is the major target of Mn toxicity within the photosynthetic apparatus of Arabidopsis plants. The possible involvement mechanisms of Mn toxicity targeting specifically PSI are discussed.

Growth, nutrition and production of dry matter of Kikuyu Grass (Brachiaria humidicula) as a function of Mn-fertilizer

“…The increase in Mn uptake due to higher availability of the nutrient in the soil increases the synthesis of nonstructural carbohydrates (Marschner, 2012) and, consequently, the synthesis of lignin, resulting in perennial leaves (Doncheva et al, 2009) and increased leaf area. However, excess of Mn is detrimental to plants and may reduce leaf biomass (Marschner, 2012;Saidi et al, 2014) by chlorophyll degradation (Papadakis et al, 2007) with consequent low carboxylation efficiency (Millaleo et al, 2013). Manganese rates affected relative chlorophyll index (RCI) at the first and second cuts, with quadratic adjustment (Fig 3).…”

“…However, the provision of 120 mg dm -3 of manganese reduced RCI in 11.92 and 29.94%, when compared to the control at the first and second cuts, respectively (Fig 3). The reduction in RCI occurs because high Mn reduces the chlorophyll biosynthesis (Wang et al, 2009) and induces reactions with oxygen, which can damage cellular macromolecules (Papadakis et al, 2007) and affect the operation of photosystem II in the photosynthesis photochemical phase (Millaleo et al, 2013).…”

“…Several factors can reduce the soil manganese content availability, such as pH higher than 6.5 (Ducic and Polle, 2005) and high levels of soil organic matter (Prado, 2008). Besides that, favorable conditions for increased bioavailability of nutrients in the soil as well as low oxygen supply (reduced atmosphere), acid pH (<5.0) or excess fertilization can cause Mn toxicity (Malavolta, 2006;Dechen and Nachtigall, 2007;Marschner, 2012;Millaleo et al, 2013;Saidi et al, 2014). Research in tropical regions have reported the importance of manganese in forage, such as Panicum maximum (Mingotte et al, 2011;Sylvestre et al, 2012) and Brachiaria brizantha (Puga et al, 2011;Guirra et al, 2011).…”

Influence of Soil Chemistry and Plant Physiology in the Phytoremediation of Cu, Mn, and Zn

“…The rice Fe transporter MIT appears to play a role in Mn transport into mitochondria (Bashir et al, 2011). The mechanisms of Mn transport in the chloroplast remain unknown, despite the fact that Mn has a critical role in photosynthesis and the chloroplast is the one of the major sinks for Mn (Millaleo et al, 2013;Yao et al, 2012).…”

Method for obtaining high-resolution proteomic analysis from pericarps of guarana

“…The contribution of different proteins including the photosystem II oxygen-evolving complex 33-kDa subunit on this photosynthetic electron transport chain, which can produce oxygen from water and light, has been vastly demonstrated (Millaleo et al, 2013). In young plants of 2 guarana clones that were grown in conditions of light stress, the greater activity involving photochemical processes (high-electron transport rate) in the tolerant clone contributed to a more significant decrease in the degree of photoinhibition compared to the sensitive clone.…”