Biology subjects

Saigo, M.

Publications and source records attributed to Saigo, M..

6 recordsLinked to original sources

bioRxiv2026

Boosting NADP-malic enzyme 1 enhances seed vigor and longevity in Arabidopsis thaliana

Seed longevity is a key determinant of crop establishment, productivity, and germplasm conservation. During storage and germination, reactive oxygen species accumulate and contribute to seed aging through oxidative damage and loss of viability. The maintenance of redox homeostasis therefore relies on NADPH-dependent antioxidant systems, which require a continuous supply of reducing power. NADP-dependent malic enzyme 1 (NADP-ME1), represents a source of NADPH supporting antioxidant defense during seed aging. Here, we show that enhanced expression of NADP-ME1 positively contributes to seed vigor and longevity in Arabidopsis thaliana. NADP-ME1 overexpression lines exhibited faster germination and higher overall germination after accelerated aging, whereas knockout mutants showed markedly reduced germination performance. Enhanced post-aging vigor in the overexpression lines was associated with reduced oxidative damage as indicated by lower malondialdehyde and hydrogen peroxide accumulation, along with preservation of specific polyunsaturated fatty acids, and increased {gamma}-tocopherol levels in aged dry seeds. Enhanced expression of NADP-ME1 reshapes the transcriptome of germinated seeds under fresh conditions compared with the wild type, while only minimal differences between genotypes are detected in aged seeds. These results suggest that NADP-ME1 contributes to the establishment of a transcriptional state associated with enhanced seed vigor and improved post-aging germination. Finally, co-immunoprecipitation coupled to mass spectrometry and bimolecular fluorescence complementation identified aspartate aminotransferase 2 as a NADP-ME1 interactor, pointing to a link between malate metabolism and amino acid-related metabolic adjustment. Together, these results identify NADP-ME1 as a determinant of seed resilience to aging and a potential target for improving seed quality.

plant biology↗

bioRxiv2026

NADP-malic enzyme 1 couples ABA signaling to ROS-auxin patterning to restrict Arabidopsis root growth

Abscisic acid (ABA) restricts primary root growth by reshaping reactive oxygen species (ROS) dynamics and hormone signaling at the root apex, yet how cellular reductant supply for redox homeostasis is integrated into this response remains unclear. Here, we show that the cytosolic NADP-dependent malic enzyme 1 (NADP-ME1) is required for full ABA inhibition of Arabidopsis primary root elongation after germination. Three independent me1 loss-of-function mutants retained significant elongation of primary roots under ABA compared with wild type. In wild type, ABA induced an asymmetric auxin response at the root tip, whereas me1 roots failed to establish this auxin asymmetry and instead accumulated superoxide, indicating disrupted ROS balance. Pharmacological perturbation of auxin transport and ethylene biosynthesis/signaling attenuated the mutant phenotype, linking NADP-ME1 function to auxin-ethylene interactions during ABA-regulated growth. NADP-ME1 loss amplifies ABA-dependent transcriptional rewiring, including induction of oxidative stress and depression of growth-associated hormone modules. Co-immunoprecipitation coupled with bimolecular fluorescence complementation identified ascorbate peroxidase 1 (APX1) and major latex protein-like 34 (MLP34) as NADP-ME1 interaction partners, suggesting functional coupling between NADPH production and ROS detoxification. Together, our results support a model in which NADP-ME1 shapes the superoxide/H2O2 balance to control auxin patterning at the root tip and thereby execute ABA-mediated growth inhibition.

plant biology↗

bioRxiv2025

Protein characterization of the soybean malic enzyme family to select metabolic targets for seed oil improvement

Seeds are of great economic interest due to their organic composition. The metabolic pathways leading to the deposition of seed storage compounds, such as oil and proteins, are complex in terms of the number of enzymes involved, the regulatory context, and the variability among species. Previous studies indicated that mitochondrial NAD-dependent and plastidial NADP-dependent malic enzymes (MEs; EC 1.1.1.39 and 1.1.1.40, respectively) participate in providing reducing power and citrate or acetyl-CoA, respectively, to fatty acid biosynthesis in soybean (Glycine max L. Merr.) embryos. In this work, we analyzed the biochemical properties of enzymes belonging to the soybean ME family; which were obtained by recombinant expression and subsequent affinity purification. Our results show that NADP-ME1.1 has high affinity for the substrates malate and NADP and is specifically activated by glutamine, the main nitrogenous compound imported from maternal tissues to support the filling process. In addition, NAD-MEs exhibit differential kinetic parameters and regulation by key metabolites, making the isoforms better suited to fulfill non-redundant functions under certain physiological conditions. Activation by intermediates of glycolysis, the citric acid cycle, and lipogenesis indicated coordination between these pathways and malate metabolism. In turn, NAD-ME activity in soybean mitochondria would be regulated by the alternative association between linage 1 and 2 subunits. These findings provide new insights into intermediary metabolism in oilseeds and nominate specific soybean ME isoforms as biotechnological tools to be used in breeding programs.

biochemistry↗

bioRxiv2024

Intercellular compartmentation of trehalose 6-phosphate metabolism in Setaria viridis leaves

Trehalose 6-phosphate (Tre6P) is a signal metabolite that links carbon metabolism with plant development. Our current understanding of Tre6P metabolism and signalling is predominantly based on studies in Arabidopsis thaliana. Some features could be adapted to the specific physiology, anatomy, and life cycle of this C3 eudicot model species, and thus might not be representative of other angiosperms. To better understand Tre6P metabolism in monocot C4 species we used Setaria viridis, which has been widely adopted as a model for the major C4 NADP-malic enzyme subtype crop species, such as maize (Zea mays), sorghum (Sorghum bicolor) and sugarcane (Saccharum officinarum). In this work, we analysed the levels of transcripts encoding Tre6P-related enzymes in different tissues and cell types from S. viridis. The TREHALOSE-6-PHOSPHATE SYNTHASE1 transcript, its encoded protein (TPS1, the enzyme responsible for Tre6P synthesis) and Tre6P were mainly located in bundle sheath cells of S. viridis. Our results show that Tre6P is predominately synthesized and located in bundle sheath and associated cells. HighlightTrehalose 6-phosphate, a sugar signalling metabolite, is mainly present in the bundle sheath cells of Setaria viridis leaves.

plant biology↗

bioRxiv2021

Understanding C4 photosynthesis in Setaria by a proteomic and kinetic approach

Plants performing C4 photosynthesis have a higher productivity per crop area related to an optimized use of water and nutrients. This is achieved through a series of anatomical and biochemical features that allow the concentration of CO2 around RuBisCO. In C4 plants the photosynthetic reactions are distributed between two cell types, they initially fix the carbon to C4 acids within the mesophyll cells (M) and then transport these compounds to the bundle sheath cells (BS), where they are decarboxylated so that the resulting CO2 is incorporated into the Calvin cycle (CC). This work is focused on the comparative analysis of the proteins present in M and BS of Setaria viridis, a C4 model close relative of several major feed, fuel, and bioenergy grasses. The integration of kinetic and proteomic approaches agrees that the C4 compound malate is mainly decarboxylated in the chloroplasts of BS cells by NADP-malic enzyme (NADP-ME). Besides, NAD-malic enzyme (NAD-ME) located in the mitochondria could also contribute to the C4 carbon shuttle. We presented evidence of metabolic strategies that involve chloroplastic, mitochondrial and peroxisomal proteins to avoid the leakage of C4 intermediates in order to sustain an efficient photosynthetic performance. HighlightProteomic and kinetic analyses show metabolic strategies involving chloroplastic, mitochondrial and peroxisomal proteins to maintain the C4 cycle performance in parallel to other metabolic pathways.

plant biology↗

bioRxiv2018

NADP-dependent malic enzyme 1 participates in the abscisic acid response in Arabidopsis thaliana

Arabidopsis thaliana possesses three cytosolic (NADP-ME1-3) and one plastidic (NADP-ME4) NADP-dependent malic enzymes. NADP-ME2 and-ME4 show constitutive expression, in contrast to NADP-ME1 and-ME3, which are restricted to particular tissues. Here, we show that NADP-ME1 transcript and protein were almost undetectable during normal vegetative growth, but gradually increased and reached levels higher than those of the other isoforms in the latest stages of seed development. Accordingly, in knockout nadp-me1 mature seeds the total NADP-ME activity was significantly lower than in wild type mature seeds. The phenotypic analysis of nadp-me1 plants indicated alterations of seed viability and germination. Besides, the treatment with abscisic acid (ABA), NaCl and mannitol specifically induced the accumulation of NADP-ME1 in seedlings. In line with this, nadp-me1 plants show a weaker response of primary and lateral root length and stomatal opening to the presence of ABA.\n\nThe results suggest that NADP-ME1 plays a specialized role, linked to ABA signalling during the seed development as well as in the response to saline and osmotic stress.

plant biology↗