Enzymatic and quantitative properties of Rubisco in some conifers and lycopods.

Information on the kinetic properties of Rubisco, a key enzyme for photosynthesis, is scarce in land plants that emerged early during the evolutionary process. This study examined the carboxylase activity and abundance of Rubisco in five conifers, two lycopods, and three control C crops. The turnover rates of Rubisco carboxylation (k) under saturated-CO conditions in conifers and lycopods were comparable to those in the control C crops.

Regulation of photosystems II and I depending on N partitioning to Rubisco in rice leaves: a study using Rubisco-antisense transgenic plants.

We have previously suggested that in rice (Oryza sativa L.) leaves of different ages and N nutrition statuses, photosystems II and I (PSII and PSI, respectively) are regulated depending on N partitioning to Rubisco, which can determine the magnitude of unutilized light energy. The robustness of this mechanism was tested using Rubisco-antisense transgenic rice plants, in which reduced N partitioning to Rubisco markedly increases unutilized light energy.

Equisetum praealtum and E. hyemale have abundant Rubisco with a high catalytic turnover rate and low CO affinity.

The kinetic properties of Rubisco, a key enzyme for photosynthesis, have been examined in numerous plant species. However, this information on some plant groups, such as ferns, is scarce. This study examined Rubisco carboxylase activity and leaf Rubisco levels in seven ferns, including four Equisetum plants (E.

Contribution of the grain size QTL to yield properties and physiological nitrogen-use efficiency in the large-grain rice cultivar 'Akita 63'.

The development of crop varieties with high nitrogen-use efficiency (NUE) is thought to be important in achieving sustainable cereal crop production. The high yield large-grain rice cultivar L. 'Akita 63' ( ) has high physiological NUE (PNUE) for grain yield (GY).

Behavior of Photosystems II and I Is Modulated Depending on N Partitioning to Rubisco in Mature Leaves Acclimated to Low N Levels and Senescent Leaves in Rice.

In mature leaves acclimated to low N levels and in senescent leaves, photosystems II and I (PSII and PSI, respectively) show typical responses to excess light energy. As CO2 assimilation is not transiently suppressed in these situations, the behavior of PSII and PSI is likely caused by endogenous biochemical changes in photosynthesis. In this study, this subject was studied in rice (Oryza sativa L.

Enhancing photosynthesis and yield in rice with improved N use efficiency.

The success of the dwarf breeding of rice, called the Green Revolution in Asia, resulted from increased source and sink capacities depending on significant inputs of N fertilizer. Although N fertilization is essential for increasing cereal production, large inputs of N application have significantly impacted the environment. Transgenic rice overproducing Rubisco has demonstrated increased yields with improved N use efficiency for increasing biomass production under high N fertilization in a paddy field.

Overexpression of Chloroplast Triosephosphate Isomerase Marginally Improves Photosynthesis at Elevated CO2 Levels in Rice.

We recently suggested that chloroplast triosephosphate isomerase (cpTPI) has moderate control over the rate of CO2 assimilation (A) at elevated CO2 levels via the capacity for triose phosphate utilization (TPU) in rice (Oryza sativa L.) from its antisense-suppression study. In the present study, the effects of cpTPI overexpression on photosynthesis were examined in transgenic rice plants overexpressing the gene encoding cpTPI.

The allele from a large-grain rice cultivar, Akita 63, increases yield and improves nitrogen-use efficiency.

The Green Revolution allowed a large amount of nitrogen (N) fertilization to increase crop yield but has led to severe environmental pollution. Therefore, increasing the crop grain yield must be achieved without such considerable input of N fertilization. A large-grain rice cultivar, Akita 63, significantly increased grain yield and improved N-use efficiency (NUE) for yield per amount of N absorbed by plants.

Effects of suppression of chloroplast phosphoglycerate kinase on photosynthesis in rice.

As chloroplast phosphoglycerate kinase (cpPGK) is one of the enzymes which has the highest capacity among the Calvin-Benson cycle enzymes, it has not been regarded as a determinant for photosynthetic capacity. However, it was reported that the rate of CO assimilation decreased under high irradiance and normal [CO] levels in the Arabidopsis cpPGK-knockdown mutant, implying that cpPGK has a control over photosynthetic capacity at a normal [CO] level. In the present study, the contribution of cpPGK to photosynthetic capacity was evaluated in transgenic rice plants with decreased amounts of cpPGK protein under high irradiance and various [CO] levels.

Photosynthetic Enhancement, Lifespan Extension, and Leaf Area Enlargement in Flag Leaves Increased the Yield of Transgenic Rice Plants Overproducing Rubisco Under Sufficient N Fertilization.

Background: Improvement in photosynthesis is one of the most promising approaches to increase grain yields. Transgenic rice plants overproducing Rubisco by 30% (RBCS-sense rice plants) showed up to 28% increase in grain yields under sufficient nitrogen (N) fertilization using an isolated experimental paddy field (Yoon et al. in Nat Food 1:134-139, 2020).

Expression of flavodiiron protein rescues defects in electron transport around PSI resulting from overproduction of Rubisco activase in rice.

Fragility of photosystem I has been observed in transgenic rice plants that overproduce Rubisco activase (RCA). In this study, we examined the effects of RCA overproduction on the sensitivity of PSI to photoinhibition in three lines of plants overexpressing RCA (RCA-ox). In all the RCA-ox plants the quantum yield of PSI [Y(I)] decreased whilst in contrast the quantum yield of acceptor-side limitation of PSI [Y(NA)] increased, especially under low light conditions.

Manganese toxicity disrupts indole acetic acid homeostasis and suppresses the CO assimilation reaction in rice leaves.

Despite the essentiality of Mn in terrestrial plants, its excessive accumulation in plant tissues can cause growth defects, known as Mn toxicity. Mn toxicity can be classified into apoplastic and symplastic types depending on its onset. Symplastic Mn toxicity is hypothesised to be more critical for growth defects.

GFS9 Affects Piecemeal Autophagy of Plastids in Young Seedlings of Arabidopsis thaliana.

Chloroplasts, and plastids in general, contain abundant protein pools that can be major sources of carbon and nitrogen for recycling. We have previously shown that chloroplasts are partially and sequentially degraded by piecemeal autophagy via the Rubisco-containing body. This degradation occurs during plant development and in response to the environment; however, little is known about the fundamental underlying mechanisms.

Overexpression of both Rubisco and Rubisco activase rescues rice photosynthesis and biomass under heat stress.

Global warming threatens food security by decreasing crop yields through damage to photosynthetic systems, especially Rubisco activation. We examined whether co-overexpression of Rubisco and Rubisco activase improves the photosynthetic and growth performance of rice under high temperatures. We grew three rice lines-the wild-type (WT), a Rubisco activase-overexpressing line (oxRCA) and a Rubisco- and Rubisco activase-co-overexpressing line (oxRCA-RBCS)-and analysed photosynthesis and biomass at 25 and 40°C.

Co-overproducing Rubisco and Rubisco activase enhances photosynthesis in the optimal temperature range in rice.

Rubisco limits C3 photosynthesis under some conditions and is therefore a potential target for improving photosynthetic efficiency. The overproduction of Rubisco is often accompanied by a decline in Rubisco activation, and the protein ratio of Rubisco activase (RCA) to Rubisco (RCA/Rubisco) greatly decreases in Rubisco-overproducing plants (RBCS-ox). Here, we produced transgenic rice (Oryza sativa) plants co-overproducing both Rubisco and RCA (RBCS-RCA-ox).

Photochemistry of Photosystems II and I in Rice Plants Grown under Different N Levels at Normal and High Temperature.

Although N levels affect leaf photosynthetic capacity, the effects of N levels on the photochemistry of photosystems II and I (PSII and PSI, respectively) are not well-understood. In the present study, we examined this aspect in rice (Oryza sativa L. 'Hitomebore') plants grown under three different N levels at normal or high temperatures that can occur during rice culture and do not severely suppress photosynthesis.

Intrinsic Fluctuations in Transpiration Induce Photorespiration to Oxidize P700 in Photosystem I.

Upon exposure to environmental stress, the primary electron donor in photosystem I (PSI), P700, is oxidized to suppress the production of reactive oxygen species that could oxidatively inactivate the function of PSI. The illumination of rice leaves with actinic light induces intrinsic fluctuations in the opening and closing of stomata, causing the net CO assimilation rate to fluctuate. We examined the effects of these intrinsic fluctuations on electron transport reactions.

Overproduction of Chloroplast Glyceraldehyde-3-Phosphate Dehydrogenase Improves Photosynthesis Slightly under Elevated [CO2] Conditions in Rice.

Chloroplast glyceraldehyde-3-phosphate dehydrogenase (GAPDH) limits the regeneration of ribulose 1,5-bisphosphate (RuBP) in the Calvin-Benson cycle. However, it does not always limit the rate of CO2 assimilation. In the present study, the effects of overproduction of GAPDH on the rate of CO2 assimilation under elevated [CO2] conditions, where the capacity for RuBP regeneration limits photosynthesis, were examined in transgenic rice (Oryza sativa).

Photorespiration Coupled With CO Assimilation Protects Photosystem I From Photoinhibition Under Moderate Poly(Ethylene Glycol)-Induced Osmotic Stress in Rice.

Photorespiration coupled with CO assimilation is thought to act as a defense system against photoinhibition caused by osmotic stress. In the present study, we examined whether such a mechanism is operative for the protection of photosystem I (PSI) in rice ( L.) including transgenic plants with decreased and increased Rubisco content (-antisense and -sense plants, respectively).

High yielding ability of a large-grain rice cultivar, Akita 63.

To increase the yield potential while limiting the environmental impact of N management practices is an important issue in rice cultivation. The large-grain rice cultivar Akita 63 showed higher N-use efficiency for grain production. To elucidate this, we analyzed yield characteristics of Akita 63 in comparison with those of a maternal cultivar, Oochikara with a large grain, a paternal cultivar, Akita 39 with a normal grain, and a Japanese leading cultivar, Akitakomachi.

Effects of Overproduction of Rubisco Activase on Rubisco Content in Transgenic Rice Grown at Different N Levels.

It has been reported that overproduction of Rubisco activase (RCA) in rice ( L.) decreased Rubisco content, resulting in declining photosynthesis. We examined the effects of RCA levels on Rubisco content using transgenic rice with overexpressed or suppressed under the control of different promoters of the and Rubisco small subunit () genes.

Transgenic rice overproducing Rubisco exhibits increased yields with improved nitrogen-use efficiency in an experimental paddy field.

The green revolution's breeding of semi-dwarf rice cultivars in the 1960s improved crop yields, with large increases in the use of nitrogen (N) fertilizer. However, excess N application has caused serious environmental problems, including acid rain and the eutrophication of rivers and oceans. To use N to improve crop yields, while minimizing the associated environmental costs, there is a need to produce crops with higher N-use efficiency and higher yield components.