Biology subjects

Calace, P.

Publications and source records attributed to Calace, P..

3 recordsLinked to original sources

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↗