The impact of interventions in the global land and agri‐food sectors on Nature’s Contributions to People and the UN Sustainable Development Goals

Interlocked challenges of climate change, biodiversity loss, and land degradation require transformative interventions in the land management and food production sectors to reduce carbon emissions, strengthen adaptive capacity, and increase food security. However, deciding which interventions to pursue and understanding their relative co‐benefits with and trade‐offs against different social and environmental goals have been difficult without comparisons across a range of possible actions. This study examined 40 different options, implemented through land management, value chains, or risk management, for their relative impacts across 18 Nature's Contributions to People (NCPs) and the 17 Sustainable Development Goals (SDGs). We find that a relatively small number of interventions show positive synergies with both SDGs and NCPs with no significant adverse trade‐offs; these include improved cropland management, improved grazing land management, improved livestock management, agroforestry, integrated water management, increased soil organic carbon content, reduced soil erosion, salinization, and compaction, fire management, reduced landslides and hazards, reduced pollution, reduced post‐harvest losses, improved energy use in food systems, and disaster risk management. Several interventions show potentially significant negative impacts on both SDGs and NCPs; these include bioenergy and bioenergy with carbon capture and storage, afforestation, and some risk sharing measures, like commercial crop insurance. Our results demonstrate that a better understanding of co‐benefits and trade‐offs of different policy approaches can help decision‐makers choose the more effective, or at the very minimum, more benign interventions for implementation.     

Regulation of bifunctional proteins in cells: Lessons from the phospholipase Cβ/G protein pathway

Some proteins can serve multiple functions depending on different cellular conditions. An example of a bifunctional protein is inositide‐specific mammalian phospholipase Cβ (PLCβ). PLCβ is activated by G proteins in response to hormones and neurotransmitters to increase intracellular calcium. Recently, alternate cellular function(s) of PLCβ have become uncovered. However, the conditions that allow these different functions to be operative are unclear. Like many mammalian proteins, PLCβ has a conserved catalytic core along with several regulatory domains. These domains modulate the intensity and duration of calcium signals in response to external sensory information, and allow this enzyme to inhibit protein translation in a noncatalytic manner. In this review, we first describe PLCβ's cellular functions and regulation of the switching between these functions, and then discuss the thermodynamic considerations that offer insight into how cells manage multiple and competitive associations allowing them to rapidly shift between functional states.     

Pelagic denitrification and methane oxidation in oxygen-depleted waters of the Louisiana shelf

Anthropogenic nutrient inputs fuel eutrophication and hypoxia ([O₂]?<?2 mg L^?1), threatening coastal and near shore environments across the globe. The world’s second largest anthropogenic coastal hypoxic zone occurs annually along the Louisiana (LA) shelf. Springtime loading of dissolved inorganic nitrogen (DIN) from the Mississippi River, combined with summertime stratification and increased water residence time on the shelf, promotes establishment of an extensive hypoxic zone that persists throughout the summer. We investigated the patterns of pelagic denitrification and methane (CH₄) oxidation along the LA shelf. Microbial activity rates were determined along with concentrations of dissolved nutrients and greenhouse gases, nitrous oxide (N₂O) and CH₄, during summer in 2013, 2015, and 2016. We documented denitrification rates up to 1900 nmol N L^?1 d^?1 and CH₄ oxidation rates as high as 192 nmol L^?1 d^?1 in hypoxic waters characterized by high concentrations of N₂O (range: 1 to 102 nM) and CH₄ (range: 3 to 641 nM). Ecosystem scaling estimates suggest that pelagic denitrification could remove between 0.1 and 47% of the DIN input from the Mississippi River, whereas CH₄ oxidation does not function as an effective removal process with CH₄ escaping to the atmosphere. Denitrification and CH₄ oxidizing bacteria within the LA shelf hypoxic zone were largely unable to keep up with the DIN and CH₄ inputs to the water column. Rates were variable and physiochemical dynamics appeared to regulate the microbial removal capacity for both nitrate/nitrite and CH₄ in this ecosystem.

     

Dynamics underlying hydroxylation selectivity of cytochrome P450cam

Structural heterogeneity and the dynamics of the complexes of enzymes with substrates can determine the selectivity of catalysis; however, fully characterizing how remains challenging as heterogeneity and dynamics can vary at the spatial level of an amino acid residue and involve rapid timescales. We demonstrate the nascent approach of site-specific two-dimensional infrared (IR) spectroscopy to investigate the archetypical cytochrome P450, P450cam, to better delineate the mechanism of the lower regioselectivity of hydroxylation of the substrate norcamphor in comparison to the native substrate camphor. Specific locations are targeted throughout the enzyme by selectively introducing cyano groups that have frequencies in a spectrally isolated region of the protein IR spectrum as local vibrational probes. Linear and two-dimensional IR spectroscopy were applied to measure the heterogeneity and dynamics at each probe and investigate how they differentiate camphor and norcamphor recognition. The IR data indicate that the norcamphor complex does not fully induce a large-scale conformational change to a closed state of the enzyme adopted in the camphor complex. Additionally, a probe directed at the bound substrate experiences rapidly interconverting states in the norcamphor complex that explain the hydroxylation product distribution. Altogether, the study reveals large- and small-scale structural heterogeneity and dynamics that could contribute to selectivity of a cytochrome P450 and illustrates the approach of site-selective IR spectroscopy to elucidate protein dynamics.