Human development, greenhouse gas emissions and sub-national mitigation burdens: a Brazilian perspective.

International frameworks for greenhouse gas (GHG) mitigation usually disregard country-specific inequalities for the allocation of mitigation burdens. This may hinder low developed regions in a country from achieving development in a socioeconomic perspective, such as the Sustainable Development Goals (SDGs) of eradicating poverty (SDG1) and hunger (SDG2). We use observed data (1991-2010) of carbon dioxide equivalent (CO2eq) emissions and a sub-national human development index (MicroHDI, range [0, 1]) for Brazilian microregions to design a framework where regional mitigation burdens are proportional to the MicroHDI, without compromising national mitigation pledges. According to our results, the less developed Brazilian regions have not been basing their development in emission-intensive activities; instead, the most developed regions have. Between 2011 and 2050, Brazilian cumulative emissions from the sectors most correlated with MicroHDI are expected to be 325 Gt CO2eq, of which only 50 Gt are associated with regions of MicroHDI < 0.8. Assuming a national GHG mitigation target of 56.5% in 2050 over 2010 (consistent with limiting global warming to 2 ºC), Brazil would emit 190 Gt CO2eq instead of 325 Gt and the 135 Gt reduction is only accounted for by regions after reaching MicroHDI ≥ 0.8. Allocating environmental restrictions to the high-developed regions leaves ground for the least developed ones to pursue development with fewer restrictions. Our heterogeneous framework represents a fairer allocation of mitigation burdens which could be implemented under the concepts of green economy. This work could be an international reference for addressing both environmental and socioeconomic development in developing countries at sub-national level as emphasized by the SDGs. Supplementary Information: The online version contains supplementary material available at 10.1007/s43621-021-00044-9.

Biochemical and functional characterization of a mitochondrial citrate carrier in Arabidopsis thaliana.

A homolog of the mitochondrial succinate/fumarate carrier from yeast (Sfc1p) has been found in the Arabidopsis genome, named AtSFC1. The AtSFC1 gene was expressed in Escherichia coli, and the gene product was purified and reconstituted in liposomes. Its transport properties and kinetic parameters demonstrated that AtSFC1 transports citrate, isocitrate and aconitate and, to a lesser extent, succinate and fumarate. This carrier catalyzes a fast counter-exchange transport as well as a low uniport of substrates, exhibits a higher transport affinity for tricarboxylates than dicarboxylates, and is inhibited by pyridoxal 5'-phosphate and other inhibitors of mitochondrial carriers to various degrees. Gene expression analysis indicated that the AtSFC1 transcript is mainly present in heterotrophic tissues, and fusion with a green-fluorescent protein localized AtSFC1 to the mitochondria. Furthermore, 35S-AtSFC1 antisense lines were generated and characterized at metabolic and physiological levels in different organs and at various developmental stages. Lower expression of AtSFC1 reduced seed germination and impaired radicle growth, a phenotype that was related to reduced respiration rate. These findings demonstrate that AtSFC1 might be involved in storage oil mobilization at the early stages of seedling growth and in nitrogen assimilation in root tissue by catalyzing citrate/isocitrate or citrate/succinate exchanges.

Downregulation of a Mitochondrial NAD+ Transporter (NDT2) Alters Seed Production and Germination in Arabidopsis.

Despite the fundamental importance of nicotinamide adenine dinucleotide (NAD+) for metabolism, the physiological roles of NAD+ carriers in plants remain unclear. We previously characterized the Arabidopsis thaliana gene (At1g25380), named AtNDT2, encoding a protein located in the mitochondrial inner membrane, which imports NAD+ from the cytosol using ADP and AMP as counter-exchange substrates for NAD+. Here, we further investigated the physiological roles of NDT2, by isolating a T-DNA insertion line, generating an antisense line and characterizing these genotypes in detail. Reduced NDT2 expression affected reproductive phase by reducing total seed yield. In addition, reduced seed germination and retardation in seedling establishment were observed in the mutant lines. Moreover, remarkable changes in primary metabolism were observed in dry and germinated seeds and an increase in fatty acid levels was verified during seedling establishment. Furthermore, flowers and seedlings of NDT2 mutants displayed upregulation of de novo and salvage pathway genes encoding NAD+ biosynthesis enzymes, demonstrating the transcriptional control mediated by NDT2 activity over these genes. Taken together, our results suggest that NDT2 expression is fundamental for maintaining NAD+ balance amongst organelles that modulate metabolism, physiology and developmental processes of heterotrophic tissues.

Nitrogen-Use Efficiency, Nitrous Oxide Emissions, and Cereal Production in Brazil: Current Trends and Forecasts.

The agriculture sector has historically been a major source of greenhouse gas (GHG) emissions into the atmosphere. Although the use of synthetic fertilizers is one of the most common widespread agricultural practices, over-fertilization can lead to negative economic and environmental consequences, such as high production costs, depletion of energy resources, and increased GHG emissions. Here, we provide an analysis to understand the evolution of cereal production and consumption of nitrogen (N) fertilizers in Brazil and to correlate N use efficiency (NUE) with economic and environmental losses as N2O emissions. Our results show that the increased consumption of N fertilizers is associated with a large decrease in NUE in recent years. The CO2 eq. of N2O emissions originating from N fertilization for cereal production were approximately 12 times higher in 2011 than in 1970, indicating that the inefficient use of N fertilizers is directly related to environmental losses. The projected N fertilizer forecasts are 2.09 and 2.37 million ton for 2015 and 2023, respectively. An increase of 0.02% per year in the projected NUE was predicted for the same time period. However, decreases in the projected CO2 eq. emissions for future years were not predicted. In a hypothetical scenario, a 2.39% increase in cereal NUE would lead to $ 21 million savings in N fertilizer costs. Thus, increases in NUE rates would lead not only to agronomic and environmental benefits but also to economic improvement.