Search

It is believed that organisms that first appeared after the formation of the earth lived in a very limited environment, making full use of the limited number of genes. From these early organisms' genes, more were created by replication, mutation, recombination, translocation, and transmission of other organisms' DNA; thus, it became possible for ancient organisms to grow in various environments. The photosynthetic CO2-fixing enzyme RuBisCO (ribulose 1,5-bisphosphate carboxylase/oxygenase) began to function in primitive methanogenic archaea and has been evolved as a central CO2-fixing enzyme in response to the large changes in CO2 and O2 concentrations that occurred in the subsequent 4 billion years. In this review, the processes of its adaptation to be specialized for CO2 fixation will be presented from the viewpoint of functions and structures of RuBisCO. [ABSTRACT FROM AUTHOR]

C4 plants assimilate CO2 more efficiently than C3 plants because of their C4 cycle that concentrates CO2. However, the C4 cycle requires additional ATP molecules, which may be supplied by cyclic electron flow (CEF) around photosystem I. One CEF route, which depends on a chloroplast NADH dehydrogenase-like (NDH) complex, is suggested to be crucial for C4 plants despite the low activity in C3 plants. The other route depends on proton gradient regulation 5 (PGR5) and PGR5-like photosynthetic phenotype 1 (PGRL1) and is considered a major CEF route to generate the proton gradient across the thylakoid membrane in C3 plants. However, its contribution to C4 photosynthesis is still unclear. In this study, we investigated the contribution of the two CEF routes to the NADP-malic enzyme subtype of C4 photosynthesis in Flaveria bidentis. We observed that suppressing the NDH-dependent route drastically delayed growth and decreased the CO2 assimilation rate to approximately 30% of the wild-type rate. On the other hand, suppressing the PGR5/PGRL1-dependent route did not affect plant growth and resulted in a CO2 assimilation rate that was approximately 80% of the wild-type rate. Our data indicate that the NDH-dependent CEF substantially contributes to the NADP-malic enzyme subtype of C4 photosynthesis and that the PGR5/PGRL1-dependent route cannot complement the NDH-dependent route in F. bidentis. These findings support the fact that during C4 evolution, photosynthetic electron flow may have been optimized to provide the energy required for C4 photosynthesis. [ABSTRACT FROM AUTHOR]

The article discusses the results of a study which examines the effect of enzyme catalyst on ribose metabolism of methionine salvage in Bacillus subtilis. The study showed that the MtnK catalyst demonstrated remarkable ribose kinase activity. It also mentioned the isomerization of ribose-1-phosphate and then dehydration, enolization, dephosphorylation, and dioxygenation by downstream enzymes.

The combined total annual yield of six major crops (maize, rice, wheat, cassava, soybean, and potato; Solanum tuberosum L.) amounts to 3.1 billion tons. In recent years, staple crops have begun to be used as substitutes for fossil fuel and feedstocks. The diversion of crop products to fuels and industrial feedstocks has become a concern in many countries because of competition for arable lands and increased food prices. These concerns are definitely justified; however, if plant biotechnology succeeds in increasing crop yields to double the current yields, it will be possible to divert the surplus to purposes other than food without detrimental effects. Maize, rice, wheat, and soybean bear their sink organs in the aerial parts of the plant, and potato in the underground parts. Plants with aerial storage organs cannot accumulate products beyond their capacity to support the weight of these organs. In contrast, potato has heavy storage organs that are supported by the soil. In this mini-review, we introduce strategies of intensifying potato productivity and discuss recent advances in this research area. [ABSTRACT FROM AUTHOR]

The combined total annual yield of six major crops (maize, rice, wheat, cassava, soybean, and potato; Solanum tuberosum L.) amounts to 3.1 billion tons. In recent years, staple crops have begun to be used as substitutes for fossil fuel and feedstocks. The diversion of crop products to fuels and industrial feedstocks has become a concern in many countries because of competition for arable lands and increased food prices. These concerns are definitely justified; however, if plant biotechnology succeeds in increasing crop yields to double the current yields, it will be possible to divert the surplus to purposes other than food without detrimental effects. Maize, rice, wheat, and soybean bear their sink organs in the aerial parts of the plant, and potato in the underground parts. Plants with aerial storage organs cannot accumulate products beyond their capacity to support the weight of these organs. In contrast, potato has heavy storage organs that are supported by the soil. In this mini-review, we introduce strategies of intensifying potato productivity and discuss recent advances in this research area. [ABSTRACT FROM AUTHOR]

The article discusses the results of a study which analyzes the molecular structure and responses of ATP synthase ε subunit and the effect of N-terminal acetylation on its regulation under drought stress in wild watermelon. Mass spectrometry revealed the formation of two isoforms of ε subunit of chloroplast ATP synthase with different isoelectric points. The study cited the presence or absence of an acetyl group at the N-terminus caused the structural differences of the isoforms.

In plants, drought stress coupled with high levels of illumination causes not only dehydration of tissues, but also oxidative damage resulting from excess absorbed light energy. In this study, we analyzed the regulation of electron transport under drought/high-light stress conditions in wild watermelon, a xerophyte that shows strong resistance to this type of stress. Under drought/high-light conditions that completely suppressed CO2 fixation, the linear electron flow was diminished between photosystem (PS) II and PS I, there was no photoinhibitory damage to PS II and PS I and no decrease in the abundance of the two PSs. Proteome analyses revealed changes in the abundance of protein spots representing the Rieske-type iron-sulfur protein (ISP) and I and K subunits of NAD(P)H dehydrogenase in response to drought stress. Two-dimensional electrophoresis and immunoblot analyses revealed new ISP protein spots with more acidic isoelectric points in plants under drought stress. Our findings suggest that the modified ISPs depress the linear electron transport activity under stress conditions to protect PS I from photoinhibition. The qualitative changes in photosynthetic proteins may switch the photosynthetic electron transport from normal photosynthesis mode to stress-tolerance mode. [ABSTRACT FROM AUTHOR]

The covalently bound phytochromobilin (PφB) prosthetic group is required for the diverse photoregulatory activities of all members of the phytochrome family in vascular plants, whereas by contrast, green algal and cyanobacterial phytochromes use the more reduced linear tetrapyrrole pigment phycocyanobilin (PCB). To assess the functional consequence of the substitution of PφB with PCB in plants, the phytochrome chromophore-deficient hy2 mutant of Arabidopsis was transformed with a constitutively expressed pcyA gene that encodes the cyanobacterial enzyme, PCB:ferredoxin oxidoreductase. Spectroscopic analyses of extracts from etiolated seedlings revealed that PcyA expression restored photoactive phytochrome to WT levels, albeit with blue-shifted absorption maxima, while also restoring light lability to phytochrome A. Photobiological measurements indicated that PcyA expression rescued phytochrome-mediated red high-irradiance responses, low- fluence red/far-red (FR) photoreversible responses. and very-low- fluence responses, thus confirming that PCB can functionally substitute for PφB for these photoregulatory activities. Although PcyA expression failed to rescue phytochrome A-mediated FR high-irradiance responsivity to that of WT, our studies indicate that the FR high-irradiance response is fully functional in pcyA-expressing plants but shifted to shorter wavelengths, indicating that PCB can functionally complement this phytochrome-mediated response in vascular plants. [ABSTRACT FROM AUTHOR]

The article offers an overview on a study by Wonchull Kang and colleagues regarding apoptosis and pyroptosis, which are the two main types of programmed cell death inhibited by Apaf-1 interacting protein (APIP).

In order to increase production of a useful protein by the chloroplast transformation technique, it seems to be necessary to determine the upper limit for the accumulation of a biologically active foreign protein in chloroplasts and then improve photosynthetic capacity and plant productivity. Here we show that the stromal fractions of tobacco chloroplasts could accommodate an additional 200–260 mg ml−1 of green fluorescent protein in the stroma without any inhibition of gas exchange under various light intensity and growth conditions. The minimum amount of fructose-1,6-/sedoheptulose-1,7-bisphosphatase (FBP/SBPase) limiting photosynthesis was then calculated. Analyses of the photosynthetic parameters and the metabolites of transformants into which FBP/SBPase was introduced with various types of promoter (PpsbA, Prrn, Prps2 and Prps12) indicated that a 2- to 3-fold increase in levels of FBPase and SBPase activity is sufficient to increase the final amount of dry matter by up to 1.8-fold relative to the wild-type plants. Their increases were equivalent to an increase of 99% of the additional 200–260 mg ml−1 of protein expressed in the chloroplasts could be used for the production of useful proteins in the photosynthesis-elevated transplastomic plants having FBP/SBPase. [ABSTRACT FROM AUTHOR]

Water availability is a critical determinant for the growth and ecological distribution of terrestrial plants. Although some xerophytes are unique regarding their highly developed root architecture and the successful adaptation to arid environments, virtually nothing is known about the molecular mechanisms underlying this adaptation. Here, we report physiological and molecular responses of wild watermelon (Citrullus lanatus sp.), which exhibits extraordinarily high drought resistance. At the early stage of drought stress, root development of wild watermelon was significantly enhanced compared with that of the irrigated plants, indicating the activation of a drought avoidance mechanism for absorbing water from deep soil layers. Consistent with this observation, comparative proteome analysis revealed that many proteins induced in the early stage of drought stress are involved in root morphogenesis and carbon/nitrogen metabolism, which may contribute to the drought avoidance via the enhancement of root growth. On the other hand, lignin synthesis-related proteins and molecular chaperones, which may function in the enhancement of physical desiccation tolerance and maintenance of protein integrity, respectively, were induced mostly at the later stage of drought stress. Our findings suggest that this xerophyte switches survival strategies from drought avoidance to drought tolerance during the progression of drought stress, by regulating its root proteome in a temporally programmed manner. This study provides new insights into the complex molecular networks within plant roots involved in the adaptation to adverse environments. [ABSTRACT FROM AUTHOR]