Apoplast proteome reveals that extracellular matrix contributes to multistress response in poplar

<p>Abstract</p> <p>Background</p> <p>Riverine ecosystems, highly sensitive to climate change and human activities, are characterized by rapid environmental change to fluctuating water levels and siltation, causing stress on their biological components. We have little understanding of mechanisms by which riverine plant species have developed adaptive strategies to cope with stress in dynamic environments while maintaining growth and development.</p> <p>Results</p> <p>We report that poplar (<it>Populus </it>spp.) has evolved a systems level "stress proteome" in the leaf-stem-root apoplast continuum to counter biotic and abiotic factors. To obtain apoplast proteins from <it>P. deltoides</it>, we developed pressure-chamber and water-displacement methods for leaves and stems, respectively. Analyses of 303 proteins and corresponding transcripts coupled with controlled experiments and bioinformatics demonstrate that poplar depends on constitutive and inducible factors to deal with water, pathogen, and oxidative stress. However, each apoplast possessed a unique set of proteins, indicating that response to stress is partly compartmentalized. Apoplast proteins that are involved in glycolysis, fermentation, and catabolism of sucrose and starch appear to enable poplar to grow normally under water stress. Pathogenesis-related proteins mediating water and pathogen stress in apoplast were particularly abundant and effective in suppressing growth of the most prevalent poplar pathogen <it>Melampsora</it>. Unexpectedly, we found diverse peroxidases that appear to be involved in stress-induced cell wall modification in apoplast, particularly during the growing season. Poplar developed a robust antioxidative system to buffer oxidation in stem apoplast.</p> <p>Conclusion</p> <p>These findings suggest that multistress response in the apoplast constitutes an important adaptive trait for poplar to inhabit dynamic environments and is also a potential mechanism in other riverine plant species.</p

Poplar maintains zinc homeostasis with heavy metal genes HMA4 and PCS1

Perennial woody species, such as poplar (Populus spp.) must acquire necessary heavy metals like zinc (Zn) while avoiding potential toxicity. Poplar contains genes with sequence homology to genes HMA4 and PCS1 from other species which are involved in heavy metal regulation. While basic genomic conservation exists, poplar does not have a hyperaccumulating phenotype. Poplar has a common indicator phenotype in which heavy metal accumulation is proportional to environmental concentrations but excesses are prevented. Phenotype is partly affected by regulation of HMA4 and PCS1 transcriptional abundance. Wild-type poplar down-regulates several transcripts in its Zn-interacting pathway at high Zn levels. Also, overexpressed PtHMA4 and PtPCS1 genes result in varying Zn phenotypes in poplar; specifically, there is a doubling of Zn accumulation in leaf tissues in an overexpressed PtPCS1 line. The genomic complement and regulation of poplar highlighted in this study supports a role of HMA4 and PCS1 in Zn regulation dictating its phenotype. These genes can be altered in poplar to change its interaction with Zn. However, other poplar genes in the surrounding pathway may maintain the phenotype by inhibiting drastic changes in heavy metal accumulation with a single gene transformation

Comparison of Broiler Litter and Commercial Fertilizer at Equivalent N Rates on Soil Properties

A 3-year study was conducted to determine the effects of broiler litter relative to inorganic fertilizer on soil nutrient content and quality in an upland Loring silt loam soil. Treatments included annual broiler litter rates of 0, 2.2, 4.5, 5.6, 6.7, 10.1, and 13.4 Mg ha−1 y−1 and commercial fertilizer rates of 34, 68, 90, 112, 134, and 168 kg nitrogen (N) ha−1 y−1. Broiler litter application linearly increased soil total carbon (C), microbial biomass C, extractable soil phosphorus (P), potassium (K), soil cation exchange capacity (CEC), and the stability of soil aggregate. At the highest broiler litter rate, the stability of soil aggregate was 34% greater than inorganic fertilizer. Application of broiler litter or fertilizer N at rate greater than 6.7 Mg ha−1 or 90 kg N ha−1, respectively, exceeded plant N utilization potential as evidenced by higher end-of-season soil residual nitrate (NO3)-N. Broiler litter is more effective in improving soil physical, chemical, and biological components than conventional fertilizer

Temporal flux and spatial dynamics of nutrients, fecal indicators, and zoonotic pathogens in anaerobic swine manure lagoon water

Confined animal feeding operations (CAFOs) often use anaerobic lagoons for manure treatment. In the USA, swine CAFO lagoon water is used for crop irrigation that is regulated by farm-specific nutrient management plans (NMPs). Implementation of stricter US environmental regulations in 2013 will set soil P limits; impacting land applications of manure and requiring revision of NMPs. Precise knowledge of lagoon water quality is needed for formulating NMPs, for understanding losses of N and C in ammonia and greenhouse gas emissions, and for understanding risks of environmental contamination by fecal bacteria, including zoonotic pathogens. In this study we determined year-round levels of nutrients and bacteria from swine CAFO lagoon water. Statistical analysis of data for pH, electrical conductivity (EC), inorganic and organic C, total N, water-soluble and total minerals (Ca, Cu, Fe, K, Mg, Mn, P, and Zn) and bacteria (Escherichia coli, enterococci, Clostridium perfringens, Campylobacter spp., Listeria spp., Salmonella spp., and staphylococci) showed that all differed significantly by dates of collection. During the irrigation season, levels of total N decreased by half and the N:P ratio changed from 9.7 to 2.8. Some seasonal differences were correlated with temperature. Total N and inorganic C increased below 19°C, and decreased above 19°C, consistent with summer increases in ammonia and greenhouse gas emissions. Water-soluble Cu, Fe, and Zn increased with higher summer temperatures while enterococci and zoonotic pathogens (Campylobacter, Listeria, and Salmonella) decreased. Although their populations changed seasonally, the zoonotic pathogens were present year-round. Increasing levels of E. coli were statistically correlated with increasing pH. Differences between depths were also found. Organic C, total nutrients (C, Ca, Cu, Fe, Mg, Mn, N, P, and Zn) and C. perfringens were higher in deeper samples, indicating stratification of these parameters. No statistical interactions were found between collection dates and depths

A Model to Estimate Hydrological Processes and Water Budget in an Irrigation Farm Pond A Model to Estimate Hydrological Processes and Water Budget in an Irrigation Farm Pond

Abstract With increased interest to conserve groundwater resources without reducing crop yield potential, more on-farm water storage ponds have been constructed in recent years in USA and around the world. However, the hydrological processes, water budget, and environmental benefits and consequences of these ponds have not yet been fully quantified. This study developed a computer model to estimate farm pond hydrological processes and water budgets using the STELLA (Structural Thinking and Experiential Learning Laboratory with Animation) software. The model was applied, as demonstrations, to estimate the diurnal and seasonal pond hydrological processes and water budget at Metcalf Farm (33 o 39′ 48″ N, 90 o 39′ 12″W) in Porter Bayou Watershed located in Mississippi Delta, USA. Two simulation scenarios were chosen in this study, one without and the other with pumping pond water for soybeans irrigation. Simulations showed that the evaporative loss of water from the pond was minimal, while the runoff water from rainfall was a major source of water entering into the pond. Therefore, factors that would affect surface water runoff should be considered in locating and sizing a farm pond in Mississippi. The seasonal rainwater and runoff water collected by the pond was: winter &gt; spring &gt; summer &gt; fall, which corresponded well to the seasonal rainfall events; whereas seasonal order of pond evaporation was: summer &gt; spring &gt; fall &gt; winter, which corresponded well to the seasonal solar radiation and air temperature. The STELLA model developed proved to be a useful tool for estimating pond water budget and consequently irrigation practices for crops. Water Resour Manag

Early-season maize responses to salt stress: Morpho-physiological, leaf reflectance, and mineral composition

Salt stress is a major environmental factor that affects maize production. The impact of salt stress during the early vegetative stage inhibits growth and development. In this study, two maize hybrids, A6659 and P1316, were subjected to five salinity treatments with electrical conductivity 0, 3, 6, 9, and 12 dS m−1 for 28 days. A total of 26 traits were evaluated, including morpho-physiological, biomass, leaf reflectance, and mineral composition in two independent studies. Under salt stress, stomatal conductance and transpiration were reduced, resulting in a canopy temperature rise of 4 °C. A higher salinity level (12 dS m−1) reduced plant height (47%) and total leaf area (44%), consequently reducing total shoot dry weight (37%) and total root dry weight (24%). Leaf minerals such as potassium, magnesium, and phosphorous declined with increasing salt concentrations. The elevated salt concentration in the rhizosphere caused an increase in leaf reflectance at the near-infrared (NIR) region, which is attributed to macronutrient deficiency under stress conditions. The results demonstrated that maize could withstand salt stress up to 3 dS m−1, beyond which plant performance declines depending on the genetics. This study provides insights into key traits that can be used for screening or breeding maize for early-season salt stress tolerance

Plant-based FRET biosensor discriminates environmental zinc levels

Summary Heavy metal accumulation in the environment poses great risks to flora and fauna. However, monitoring sites prone to accumulation poses scale and economic challenges. In this study, we present and test a method for monitoring these sites using fluorescent resonance energy transfer (FRET) change in response to zinc (Zn) accumulation in plants as a proxy for environmental health. We modified a plant Zn transport protein by adding flanking fluorescent proteins (FPs) and deploying the construct into two different species. In Arabidopsis thaliana, FRET was monitored by a confocal microscope and had a 1.4-fold increase in intensity as the metal concentration increased. This led to a 16.7% overall error-rate when discriminating between a control (1 lM Zn) and high (10 mM Zn) treatment after 96 h. The second host plant (Populus tremula · Populu salba) also had greater FRET values (1.3-fold increase) when exposed to the higher concentration of Zn, while overall error-rates were greater at 22.4%. These results indicate that as plants accumulate Zn, protein conformational changes occur in response to Zn causing differing interaction between FPs. This results in greater FRET values when exposed to greater amounts of Zn and monitored with appropriate light sources and filters. We also demonstrate how this construct can be moved into different host plants effectively including one tree species. This chimeric protein potentially offers a method for monitoring large areas of land for Zn accumulation, is transferable among species, and could be modified to monitor other specific heavy metals that pose environmental risks

Effects of Cover Crops and Soil Amendments on Soil CO₂ Flux in a Mississippi Corn Cropping System on Upland Soil

Agroecosystems, accounting for more than one-third of arable land worldwide, play an essential role in the terrestrial carbon (C) cycle. The development of agricultural practices, which maximize soil C sequestration from the atmosphere, is receiving growing attention due to the recognition of agroecosystems’ great potential to serve as sinks of atmospheric carbon dioxide (CO2). In particular, cover crop and soil amendment applications are generating much interest in mitigating climate change and enhancing agricultural ecosystem services. The objective of this study was to evaluate the effects of winter cover crop and soil amendments, including broiler litter (BL), flue gas desulfurization (FGD) gypsum and lignite, on soil CO2 flux from cropping systems in southeastern USA, where related studies were limited. A field study was conducted from 2019 to 2021 in a Mississippi upland corn cropping system with measurements of soil CO2 flux, moisture and temperature during cash crop growing seasons. We observed high temporal variability in soil CO2 flux with flux peaks between late June and early July, which is likely due to the temporal changes in soil moisture. A significant increase in soil CO2 flux was found with BL application (p 2 flux by 15–23% but did not fully eliminate the rising effects. Significantly higher soil CO2 flux and lower soil temperature were observed from fields with cover crops than those without cover crops in the third year of this study (p < 0.05), which is likely attributed to the higher organic C content accumulated in soil with cover crops. Future research should assess year-round soil greenhouse gas fluxes in both cash crop and cover crop growing seasons using a high temporal resolution measurement scheme