![]() In the past, Mn transporters have been identified at the molecular level in many eukaryotic organisms ( Pittman, 2005). Transport processes are at the core of those adaptations. On the other extreme, Mn toxicity can occur in poorly drained and in strongly acidic soils, where it is usually associated with other acidity-related soil fertility problems, such as aluminum toxicity and deficiencies of calcium (Ca), magnesium (Mg), and molybdenum (Mo) ( Goulding, 2016).ĭepending on Mn availability, plants either need to efficiently acquire and utililize Mn under limiting conditions, or to detoxify the metal under superfluous supply. ![]() Moreover, foliar Mn sprays are only effective for a limited time period since Mn is very little mobile in the plant and does not remobilize from older leaves to Mn-deficient young leaves ( Li et al., 2017). Foliar Mn application can supply sufficient Mn to overcome Mn deficiency, but this strategy is expensive and often impractical for farmers on marginal lands. However, it has been argued that the application of Mn fertilizers to the soil can be an effective way to alleviate Mn deficiencies, but only if soil pH is also corrected ( White and Greenwood, 2013). (In this review, we use the general term “Mn,” unless we refer to a specific oxidation state). Fertilization with Mn salts at soil level is often not effective, since soluble Mn (Mn 2+) is rapidly converted to plant-unavailable Mn oxides, particularly in sandy alkaline soils. Nevertheless, Mn deficiency can be a serious plant nutritional disorder in soils with high pH and high partial pressure of O 2 (pO 2), where the bio-availability of Mn can decrease far below the level that is required for normal plant growth ( Broadley et al., 2012). In spite of its importance for photosynthetic activity, Mn homeostasis in plants has been poorly investigated. ![]() In photosynthetic organisms, Mn is an essential element of the metalloenzyme cluster of the oxygen-evolving complex (OEC) in photosystem II (PSII). It is needed in only small quantities by plants, but is ultimately as critical to growth as are the other nutrients. In plants, Mn is one of the 17 essential elements for growth and reproduction. However, Mn poisoning may be encountered more frequently upon overexposure to this metal causing hepatic cirrhosis, polycythemia, dystonia, and Parkinson-like symptoms ( Li and Yang, 2018). But in comparison to other essential micronutrients, such as iron (Fe) and zinc (Zn), whose deficiencies in humans are responsible for major health problems, Mn deficiency in humans is rare. In humans, Mn functions as a cofactor for a variety of enzymes, including arginase, glutamine synthetase, pyruvate carboxylase, and Mn superoxide dismutase (MnSOD). Manganese (Mn) is an essential element in virtually all living organisms where it can fulfill two different functions: acting as an enzyme cofactor or as a metal with catalytic activity in biological clusters ( Andresen et al., 2018). This review provides a comprehensive overview, with a focus on recent advances, on the multiple functions of transporters involved in Mn homeostasis, as well as their regulatory mechanisms in the plant’s response to different conditions of Mn availability. Consequently, plants have evolved mechanisms to tightly regulate Mn uptake, trafficking, and storage. By contrast, Mn toxicity occurs on poorly drained and acidic soils in which high amounts of Mn are rendered available. Mn deficiency is a serious, widespread plant nutritional disorder in dry, well-aerated and calcareous soils, as well as in soils containing high amounts of organic matter, where bio-availability of Mn can decrease far below the level that is required for normal plant growth. However, Mn homeostasis may be disturbed under suboptimal or excessive Mn availability. The subcellular Mn homeostasis to maintain compartmented Mn-dependent metabolic processes like glycosylation, ROS scavenging, and photosynthesis is mediated by a multitude of transport proteins from diverse gene families. Despite the importance of Mn for photosynthesis and other processes, the physiological relevance of Mn uptake and compartmentation in plants has been underrated. The metal is an essential cofactor for the oxygen-evolving complex (OEC) of the photosynthetic machinery, catalyzing the water-splitting reaction in photosystem II (PSII). Manganese (Mn) is an important micronutrient for plant growth and development and sustains metabolic roles within different plant cell compartments.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |