Molecular mechanism of Rubisco activase: Dynamic assembly and Rubisco remodeling

Synthetic biology approaches to improve Rubisco carboxylation efficiency in C3 Plants: Direct and Indirect Strategies

Food security remains a pressing issue due to the growing global population and climate change, including the global warming along with increased atmospheric CO2 levels, which can negatively impact C3 crop yields. A major limitation in C3 plants is the inefficiency of Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) due to its low carboxylation activity and competing oxygenase activity. Improving Rubisco efficiency in C3 plants is thus essential for improving photosynthetic performance. Recent advances in synthetic biology have introduced promising strategies to overcome these limitations. This review highlights the latest synthetic biology and gene transformation techniques aimed at optimizing Rubsico carboxylation efficiency. Next, direct approaches such as engineering Rubisco subunits by replacing plant Rubisco with proteins from other organisms are discussed. Additionally, indirect strategies involve modifications of Rubisco-interacting proteins and adjustment of Rubisco environment. We explore CO2-concentrating mechanisms (CCMs) based on pyrenoids and carboxysomes, which increase local CO2 concentrations around Rubisco thus favouring the carboxylation reaction. Lastly, photorespiratory bypasses are also covered in this review.

Mechanism of Bacillus cooperating with silicon to re-balance chlorophyll metabolism and restore carbon metabolism of Glycyrrhiza uralensis Fisch. Seedlings exposed to salt-drought stress

Salt-drought is a major environmental event affecting crop productivity and quality by causing chlorophyll (Chl) and carbon balance disorder. There has been growing interest in the application of endophyte and silicon (Si), as inoculants for saline and drought land restoration. This study investigates the impact of Bacillus (Bs), Si, and Bs + Si on the disorder of Chl metabolism and carbon balance of G. uralensis seedlings under salt-drought stress (SD). Results showed that both Bs and Si treatments enhanced Chl and carbon metabolism, with the combined Bs and Si treatment showing a synergistic effect. Specifically, Bs + Si enhanced the mutual conversion of Chl a and Chl b, restored the equilibrium in Chl a and Chl b content, and increased RuBisco activity by 31.07%, thereby promoting carbon fixation. Subsequently, Bs + Si re-balanced the carbohydrate content, by increasing the sucrose synthase (SS), and β-amylase (BMY) activities by 49.57%, and 83.59% respectively, and decreasing sucrose phosphate synthase (SPS), and granule-bound starch synthase (GBSS) activities by 38.93%, 40.93% respectively etc involved in the metabolism of sucrose and starch. Furthermore, Bs + Si facilitated the restoration of the typical progression of the tricarboxylic acid (TCA) cycle and glycolysis pathway (EMP). These findings highlight the synergistic role of Bs and Si in enhancing the salt and drought resilience of G. uralensis seedlings, offering promising strategies for sustainable agriculture, improving crop resilience to climate change, and achieving the "dual carbon" goals of carbon peaking and carbon neutrality.

From algae to plants: understanding pyrenoid-based CO2-concentrating mechanisms

Pyrenoids are the key component of one of the most abundant biological CO2 concentration mechanisms found in nature. Pyrenoid-based CO2-concentrating mechanisms (pCCMs) are estimated to account for one third of global photosynthetic CO2 capture. Our molecular understanding of how pyrenoids work is based largely on work in the green algae Chlamydomonas reinhardtii. Here, we review recent advances in our fundamental knowledge of the biogenesis, architecture, and function of pyrenoids in Chlamydomonas and ongoing engineering biology efforts to introduce a functional pCCM into chloroplasts of vascular plants, which, if successful, has the potential to enhance crop productivity and resilience to climate change.

Multi-omics analysis uncovers the transcriptional regulatory mechanism of magnesium Ions in the synthesis of active ingredients in Sophora tonkinensis

Magnesium (Mg) plays a pivotal role as an essential component of plant chlorophyll and functions as a critical coenzyme. However, research exploring the regulatory mechanisms of magnesium ions on the synthesis of secondary metabolites is still in its early stages. Sophora tonkinensis is a widely utilized medicinal plant in China, recognized for its diverse secondary metabolites with active properties. This study investigates variations in these ingredients in tissue-cultured seedlings under varying magnesium concentrations. Simultaneously, an omics data analysis was conducted on tissue-cultured seedlings subjected to treatments with magnesium and low magnesium. These comprehensive omics analyses aimed to elucidate the mechanisms through which magnesium influences active components, growth, and development. Magnesium exerts a pervasive influence on various metabolic pathways, forming an intricate network. Research findings indicate that magnesium impacts diverse metabolic processes, including the absorption of potassium and calcium, as well as photosynthetic activity. Consequently, these influences lead to discernible changes in the levels of pharmacologically active compounds and the growth and developmental status.This study is the first to employ a multi-omics data analysis in S. tonkinensis. This methodology allows us to uncover the overarching impact of metabolic networks on the levels of various active ingredients and specific phenotypes.

From leaf to multiscale models of photosynthesis: applications and challenges for crop improvement

To keep up with the growth of human population and to circumvent deleterious effects of global climate change, it is essential to enhance crop yield to achieve higher production. Here we review mathematical models of oxygenic photosynthesis that are extensively used, and discuss in depth a subset that accounts for diverse approaches providing solutions to our objective. These include models (1) to study different ways to enhance photosynthesis, such as fine-tuning antenna size, photoprotection and electron transport; (2) to bioengineer carbon metabolism; and (3) to evaluate the interactions between the process of photosynthesis and the seasonal crop dynamics, or those that have included statistical whole-genome prediction methods to quantify the impact of photosynthesis traits on the improvement of crop yield. We conclude by emphasizing that the results obtained in these studies clearly demonstrate that mathematical modelling is a key tool to examine different approaches to improve photosynthesis for better productivity, while effective multiscale crop models, especially those that also include remote sensing data, are indispensable to verify different strategies to obtain maximized crop yields.

Physiological and Proteomic Responses of the Tetraploid Robinia pseudoacacia L. to High CO2 Levels

The increase in atmospheric CO2 concentration is a significant factor in triggering global warming. CO2 is essential for plant photosynthesis, but excessive CO2 can negatively impact photosynthesis and its associated physiological and biochemical processes. The tetraploid Robinia pseudoacacia L., a superior and improved variety, exhibits high tolerance to abiotic stress. In this study, we investigated the physiological and proteomic response mechanisms of the tetraploid R. pseudoacacia under high CO2 treatment. The results of our physiological and biochemical analyses revealed that a 5% high concentration of CO2 hindered the growth and development of the tetraploid R. pseudoacacia and caused severe damage to the leaves. Additionally, it significantly reduced photosynthetic parameters such as Pn, Gs, Tr, and Ci, as well as respiration. The levels of chlorophyll (Chl a and b) and the fluorescent parameters of chlorophyll (Fm, Fv/Fm, qP, and ETR) also significantly decreased. Conversely, the levels of ROS (H2O2 and O2·-) were significantly increased, while the activities of antioxidant enzymes (SOD, CAT, GR, and APX) were significantly decreased. Furthermore, high CO2 induced stomatal closure by promoting the accumulation of ROS and NO in guard cells. Through a proteomic analysis, we identified a total of 1652 DAPs after high CO2 treatment. GO functional annotation revealed that these DAPs were mainly associated with redox activity, catalytic activity, and ion binding. KEGG analysis showed an enrichment of DAPs in metabolic pathways, secondary metabolite biosynthesis, amino acid biosynthesis, and photosynthetic pathways. Overall, our study provides valuable insights into the adaptation mechanisms of the tetraploid R. pseudoacacia to high CO2.

Molecular characterization and expression pattern of Rubisco activase gene GhRCAβ2 in upland cotton (Gossypium hirsutum L.)

BACKGROUND

Rubisco activase (RCA) is a pivotal enzyme that can catalyse the activation of Rubisco in carbon assimilation pathway. Many studies have shown that RCA may be a potential target for genetic manipulation aimed at enhancing photosynthetic efficiency and crop yield.

OBJECTIVE

To understand the biological function of the GhRCAβ2 gene in upland cotton, we cloned the coding sequence (CDS) of the GhRCAβ2 gene and investigated its sequence features, evolutionary relationship, subcellular localization, promoter sequence and expression pattern.

METHODS

The bioinformatics tools were used to analyze the sequence features of GhRCAβ2 protein. Transient transformation of Arabidopsis mesophyll protoplasts was performed to determine the subcellular localization of the GhRCAβ2 protein. The expression pattern of the GhRCAβ2 gene was examined by analyzing transcriptome data and using the quantitative real-time PCR (qRT-PCR).

RESULTS

The full-length CDS of GhRCAβ2 was 1317 bp, and it encoded a protein with a chloroplast transit peptide. The GhRCAβ2 had two conserved ATP-binding domains, and did not have the C-terminal extension (CTE) domain that was unique to the RCA α-isoform in plants. Evolutionarily, GhRCAβ2 was clustered in Group A, and had a close evolutionary relationship with the soybean RCA. Western blot analysis demonstrated that GhRCAβ2 was immunoreactive to the RCA antibody displaying a molecular weight similar to that of the RCA β-isoform. The GhRCAβ2 protein was found in chloroplast, aligning with its role as a vital enzyme in the process of photosynthesis. The GhRCAβ2 gene had a leaf tissue-specific expression pattern, and the yellow-green leaf mutant exhibited a decreased expression of GhRCAβ2 in comparison to the wild-type cotton plants. The GhRCAβ2 promoter contained several cis-acting elements that respond to light, phytohormones and stress, suggesting that the expression of GhRCAβ2 may be regulated by these factors. An additional examination of stress response indicated that GhRCAβ2 expression was influenced by cold, heat, salt, and drought stress. Notably, diverse expression pattern was observed across different stress conditions. Additionally, low phosphorus and low potassium stress may result in a notable reduction in the expression of GhRCAβ2 gene.

CONCLUSION

Our findings will establish a basis for further understanding the function of the GhRCAβ2 gene, as well as providing valuable genetic knowledge to improve cotton photosynthetic efficiency and yield under challenging environmental circumstances.

Calcium-Dependent Protein Kinase 5 (OsCPK5) Overexpression in Upland Rice (Oryza sativa L.) under Water Deficit

Water deficit significantly affects global crop growth and productivity, particularly in water-limited environments, such as upland rice cultivation, reducing grain yield. Plants activate various defense mechanisms during water deficit, involving numerous genes and complex metabolic pathways. Exploring homologous genes that are linked to enhanced drought tolerance through the use of genomic data from model organisms can aid in the functional validation of target species. We evaluated the upland rice OsCPK5 gene, an A. thaliana AtCPK6 homolog, by overexpressing it in the BRSMG Curinga cultivar. Transformants were assessed using a semi-automated phenotyping platform under two irrigation conditions: regular watering, and water deficit applied 79 days after seeding, lasting 14 days, followed by irrigation at 80% field capacity. The physiological data and leaf samples were collected at reproductive stages R3, R6, and R8. The genetically modified (GM) plants consistently exhibited higher OsCPK5 gene expression levels across stages, peaking during grain filling, and displayed reduced stomatal conductance and photosynthetic rate and increased water-use efficiency compared to non-GM (NGM) plants under drought. The GM plants also exhibited a higher filled grain percentage under both irrigation conditions. Their drought susceptibility index was 0.9 times lower than that of NGM plants, and they maintained a higher chlorophyll a/b index, indicating sustained photosynthesis. The NGM plants under water deficit exhibited more leaf senescence, while the OsCPK5-overexpressing plants retained their green leaves. Overall, OsCPK5 overexpression induced diverse drought tolerance mechanisms, indicating the potential for future development of more drought-tolerant rice cultivars.