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DENSITY FUNCTIONAL THEORY --- PHOTOSYSTEM II --- OXYGENASES (MESH)

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Photosystem II is a 700-kDa membrane-protein super-complex responsible for the light-driven splitting of water in oxygenic photosynthesis. The photosystem is comprised of two 350-kDa complexes each made of 20 different polypeptides and over 80 co-factors. While there have been major advances in understanding the mature structure of this photosystem many key protein factors involved in the assembly of the complex do not appear in the holoenzyme. The mechanism for assembling this super-complex is a very active area of research with newly discovered assembly factors and subcomplexes requiring characterization. Additionally the ability to split water is inseparable from light-induced photodamage that arises from radicals and reactive O2 species generated by Photosystem II chemistry. Consequently, to sustain water splitting, a “self repair” cycle has evolved whereby damaged protein is removed and replaced so as to extend the working life of the complex. Understanding how the biogenesis and repair processes are coordinated is among several important questions that remain to be answered. Other questions include: how and when are the inorganic cofactors inserted during the assembly and repair processes and how are the subcomplexes protected from photodamage during assembly? Evidence has also been obtained for Photosystem II biogenesis centers in cyanobacteria but do these also exist in plants? Do the molecular mechanisms associated with Photosystem II assembly shed fresh light on the assembly of other major energy-transducing complexes such as Photosystem I or the cytochrome b6/f complex or indeed other respiratory complexes? The contributions to this Frontiers in Plant Science Research Topic are likely to reveal new details applicable to the assembly of a range of membrane-protein complexes, including aspects of self-assembly and solar energy conversion that may be applied to artificial photosynthetic systems. In addition, a deeper understanding of Photosystem II assembly — particularly in response to changing environmental conditions — will provide new knowledge underpinning photosynthetic yields which may contribute to improved food production and long-term food security.

Arabidopsis thaliana --- photoactivation --- photosynthesis --- Chlamydomonas reinhardtii --- cyanobacteria --- biogenesis --- Photosystem II --- photodamage --- Nicotiana tabacum --- Synechocystis sp. PCC 6803

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Photosystem II is a 700-kDa membrane-protein super-complex responsible for the light-driven splitting of water in oxygenic photosynthesis. The photosystem is comprised of two 350-kDa complexes each made of 20 different polypeptides and over 80 co-factors. While there have been major advances in understanding the mature structure of this photosystem many key protein factors involved in the assembly of the complex do not appear in the holoenzyme. The mechanism for assembling this super-complex is a very active area of research with newly discovered assembly factors and subcomplexes requiring characterization. Additionally the ability to split water is inseparable from light-induced photodamage that arises from radicals and reactive O2 species generated by Photosystem II chemistry. Consequently, to sustain water splitting, a “self repair” cycle has evolved whereby damaged protein is removed and replaced so as to extend the working life of the complex. Understanding how the biogenesis and repair processes are coordinated is among several important questions that remain to be answered. Other questions include: how and when are the inorganic cofactors inserted during the assembly and repair processes and how are the subcomplexes protected from photodamage during assembly? Evidence has also been obtained for Photosystem II biogenesis centers in cyanobacteria but do these also exist in plants? Do the molecular mechanisms associated with Photosystem II assembly shed fresh light on the assembly of other major energy-transducing complexes such as Photosystem I or the cytochrome b6/f complex or indeed other respiratory complexes? The contributions to this Frontiers in Plant Science Research Topic are likely to reveal new details applicable to the assembly of a range of membrane-protein complexes, including aspects of self-assembly and solar energy conversion that may be applied to artificial photosynthetic systems. In addition, a deeper understanding of Photosystem II assembly — particularly in response to changing environmental conditions — will provide new knowledge underpinning photosynthetic yields which may contribute to improved food production and long-term food security.

Arabidopsis thaliana --- photoactivation --- photosynthesis --- Chlamydomonas reinhardtii --- cyanobacteria --- biogenesis --- Photosystem II --- photodamage --- Nicotiana tabacum --- Synechocystis sp. PCC 6803

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Phytochemistry. Phytobiochemistry --- PLANT BIOCHEMISTRY --- AMINO ACIDS --- PROTEINS --- NUCLEIC ACIDS --- THYLAKOIDS --- PHOTOSYSTEM I --- PHOTOSYSTEM II --- ALGAE --- CHROMOPROTEINS --- PHYTOCHROME --- CYTOKININS --- PURINES --- PYRIMIDINES --- NUCLEOSIDES --- NUCLEOTIDES --- SEED PROTEINS --- CELL WALLS

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The concept of nitrogen gap (NG), i.e., its recognition and amelioration, forms the core of this book entitled Site-Specific Nutrient Management (SSNM). Determination of the presence of an NG between fields on a farm and/or within a particular field, together with its size, requires a set of highly reliable diagnostic tools. The necessary set of diagnostic tools, based classically on pedological and agrochemical methods, should be currently supported by remote-sensing methods. A combination of these two groups of methods is the only way to recognize the factors responsible for yield gap (YG) appearance and to offer a choice of measures for its effective amelioration. The NG concept is discussed in the two first papers (Grzebisz and Łukowiak, Agronomy 2021, 11, 419; Łukowiak et al., Agronomy 2020, 10, 1959). Crop productivity depends on a synchronization of plant demand for nitrogen and its supply from soil resources during the growing season. The action of nitrate nitrogen (N–NO3), resulting in direct plant crop response, can be treated by farmers as a crucial growth factor. The expected outcome also depends on the status of soil fertility factors, including pools of available nutrients and the activity of microorganisms. Three papers are devoted to these basic aspects of soil fertility management (Sulewska et al., Agronomy 2020, 10, 1958; Grzebisz et al., Agronomy 2020, 10, 1701; Hlisnikovsky et al., Agronomy 2021, 11, 1333). The resistance of a currently cultivated crop to seasonal weather variability depends to a great extent on the soil fertility level. This aspect is thoroughly discussed for three distinct soil types and climates with respect to their impact on yield (Hlisnikovsky et al., Agronomy 2020, 10, 1160—Czech Republic; Wang et al., Agronomy 2020, 10, 1237—China; Łukowiak and Grzebisz et al., Agronomy 2020, 10, 1364—Poland). In the fourth section of this book, the division a particular field into homogenous production zones is discussed as a basis for effective nitrogen management within the field. This topic is presented for different regions and crops (China, Poland, and the USA) (Cammarano et al., Agronomy 2020, 10, 1767; Panek et al., Agronomy 2020, 10, 1842; Larson et al., Agronomy 2020, 10, 1858).

Research & information: general --- Biology, life sciences --- Technology, engineering, agriculture --- Triticum aestivum L. --- farmyard manure --- mineral fertilizers --- crude protein content --- soil properties, site-specific requirements --- yield --- site-specific nitrogen management --- regional optimal nitrogen management --- net return --- nitrogen use efficiency --- spatial variability --- temporal variability --- seed density --- N uptake --- indices of N productivity --- mineral N --- indigenous Nmin at spring --- post-harvest Nmin --- N balance --- N efficiency --- maximum photochemical efficiency of photosystem II --- chlorophyll content index --- soil enzymatic activity --- biological index fertility --- nitrogenase activity --- microelements fertilization (Ti --- Si --- B --- Mo --- Zn) --- soil --- nitrate nitrogen content --- contents of available phosphorus --- potassium --- magnesium --- calcium --- cardinal stages of WOSR growth --- PCA --- site-specific nutrient management --- soil brightness --- satellite remote sensing --- crop yield --- soil fertility --- winter wheat --- winter triticale --- vegetation indices --- NDVI --- grain yield --- number of spikes --- economics --- normalized difference vegetation index (NDVI) --- on-the-go sensors --- winter oilseed rape → winter triticale cropping sequence --- N input --- N total uptake --- N gap --- Beta vulgaris L. --- organic manure --- weather conditions --- soil chemistry --- sugar concentration --- climatic potential yield --- yield gap --- soil constraints --- subsoil --- remote sensing-techniques --- field --- a field --- crop production --- sustainability --- homogenous productivity units --- nitrogen indicators: in-season --- spatial --- vertical variability of N demand and supply --- spectral imagery