SEA and GATOR 10 Years Later

The SEA complex was described for the first time in yeast Saccharomyces cerevisiae ten years ago, and its human homologue GATOR complex two years later. During the past decade, many advances on the SEA/GATOR biology in different organisms have been made that allowed its role as an essential upstream regulator of the mTORC1 pathway to be defined. In this review, we describe these advances in relation to the identification of multiple functions of the SEA/GATOR complex in nutrient response and beyond and highlight the consequence of GATOR mutations in cancer and neurodegenerative diseases.

Potential nutrient-response curves and sufficiency ranges of ‘Grande Naine’ banana cultivated in two environment

Adequate plant nutrition is essential to attain higher yields. The objective was to determine potential-nutrient response curves and sufficiency ranges using the boundary line approach and balance indices of Kenworthy for interpreting the nutritional status of ‘Grand Nain’ banana cultivated in two environments. The study was carried out using a database containing leaf nutrient concentrations and yields of bananas cultivated on two areas located in Missão Velha-CE, and Ponto Novo-BA, Brazil. Plots with high-yielding plants, which were those with yields above average plus 0.5 standard deviation, were used atem as reference population. The database was subdivided into two sets. One of them contained 46 leaf tissue samples and reference population with yield greater than 58.84 Mg ha-1 year-1, in Missão Velha-CE. The second data set contained 19 samples and reference population with yield greater than 76.12 Mg ha-1 year-1 in Ponto Novo-BA. Potential response curves were fitted to the relationship between relative yield and leaf element concentrations and balance indices of Kenworthy. Models expressed high predictive power. Sufficiency ranges for macro- and micronutrient concentrations and balance indices of Kenworthy were established. The ranges allow an improved nutritional status assessment of irrigated ‘Grand Nain’ bananas.

Nutrient saturation of crop monocultures and agroforestry indicated by nutrient response efficiency

Efficient use of nutrients is a key requisite for a sustainable intensification of agriculture in order to meet the increasing global crop demand while minimizing deleterious environmental impacts. Agroforestry systems exhibit tree–crop interactions, which potentially contribute to nutrient-efficient agro-ecosystems. Our goal was to determine whether the conversion from cropland monocultures to alley-cropping agroforestry increases nutrient response efficiency (NRE), the ability of plants to convert available nutrients into biomass. We found that crop yield, plant-available nutrients and NRE were comparable between agroforestry and monocultures, but the trees in agroforestry had high NRE, contributing to nutrient retention of the agroforestry systems as a whole. The unimodal relationship of the crops’ NRE with plant-available nutrients suggests that NRE values were beyond optimum in both agroforestry and monoculture indicating nutrient saturation. This indicates that fertilizer inputs can be reduced (or optimized) without sacrificing crop yield or profit. Based on the NRE curves, we assessed that a reduction of plant-available N by 50% would lead to a decrease in crop yield by 17% and a concomitant increase in N response efficiency by 67%, whereas a similar reduction of plant-available P would lead to a decrease in crop yield by 8% with an increase in P response efficiency by 83%. An optimized fertilization to achieve such lower levels of plant-available nutrients will have beneficial effects on nutrient retention and redistribution. Optimizing fertilizer input will make alley-cropping agroforestry a productive and profitable agro-ecosystem that contributes to an ecologically sustainable agriculture.

NtrX systemically controls transcription of the CtrA system genes to regulate Rhizobium cell division

In α-proteobacteria, the CtrA signaling pathway regulates cell cycle progression. A species whose cell duplication is associated with CtrA stability is affected by the response regulator NtrX. However, the function of NtrX acting on the cell cycle regulation in bacteria remains unclear. Here, we report that NtrX controls transcription of the CtrA system genes involved in cell cycle regulation in a legume symbiont, Sinorhizobium meliloti. Three groups of ntrX mutants showed the similar cell cycle defects, such as slow growth, abnormal shapes, and irregular genomic DNA accumulation. Expression of the CtrA signaling pathway genes including ctrA, gcrA, dnaA, divL and cpdR1, is differentially regulated by the phosphorylated NtrX protein. The regulation is achieved through direct protein-DNA interactions. The 53rd aspartate residue known as the conserved phosporylation site and located in the receiver domain of NtrX, is required for S. meliloti cell cycle regulation. Interestingly, expression of S. meliloti ntrX derivatives in Caulobacter and Agrobacterium strains showed distinct defects of cell duplication and growth, suggesting that NtrX plays different roles in cell cycle regulation in these bacteria. Our findings demonstrate that NtrX is an upstream transcriptional regulator of the CtrA signaling pathway in S. meliloti, which could be associated with nitrogen nutrient response.Author SummaryCell cycle regulation in alpha-proteobacteria is dictated by the conserved CtrA signaling pathway. Transcription of the CtrA system genes is mainly regulated by CtrA and GcrA. CcrM, SciP and MucR also participate in transcription regulation of ctrA. However, the regulation by a nutrient response regulator at transcriptional level remains unclear. Here, we report that the nitrogen response regulator, NtrX systemically regulates transcription of several CtrA system genes by protein-DNA interactions in a legume symbiont, S. meliloti. The similar mechanism is proposed in the pathogens of Agrobacterium and Brucella species. These findings provide a new prospect to understand the hierarchy of transcriptional regulation in a bacterial cell cycle.

Burn Severity Effects on Sediment and Nutrient Exports from Southeastern Forests Using Simulated Rainfall

Burn severity, commonly assessed as the amount of fuel consumed during fire, is an indicator of postfire sediment yield and erosion. This study examined the effect of burn severity on sediment and nutrient response in three different fire-adapted forest types of the Southeast. Soil and litter samples were experimentally burned to achieve increasing levels of fuel consumption. Simulated rainfall was applied to burned litter samples collected from pine, hardwood, and mixed hardwood-pine forests in the Clemson Experimental Forest. Runoff and leachate samples were collected and analyzed for sediment yield (kilograms per hectare) and total suspended solids (grams per liter); both runoff and leachate samples were analyzed for ammonium (NH4–), nitrate (NO3–), and orthophosphate (PO43–). Sediment yield and total suspended solids increased at only the highest burn severity treatment in all three forest types, with pine litter samples yielding significantly greater sediment in surface runoff than both mixed and hardwood samples. Burn treatment did not readily affect soluble nutrient concentrations in either runoff or leachate, but the data suggest that high-severity burning increases the availability of PO43– bound to sediment. This study suggests that high-severity burn patches function as sediment sources, but overall sediment and nutrient response to burning was minimal. Study Implications This study suggests that low-to-moderate burn severity, in terms of litter removal, is not an important indicator of sediment and nutrient exports from southeastern forests; precipitation in the immediate aftermath of fire (<48 hours) is not an effective transport mechanism for biologically available macronutrients; and that even at the highest burn severity treatment, sediment yield was relatively low.

Penentuan Dosis N, P, dan K Optimum untuk Padi Gogo Kultivar Mayas Lokal Kalimantan

ABSTRAK Pemupukan berimbang adalah metode yang efektif untuk meningkatkan produksi padi dan menjaga keberlanjutan lingkungan. Tujuan penelitian ini adalah untuk menentukan dosis optimum pupuk N, P, K untuk padi gogo kultivar Mayas. Penelitian dilaksanakan pada bulan Januari sampai dengan Juli 2019 di lahan Kebun Percobaan Leuwikopo, IPB University, Bogor. Percobaan terdiri atas tiga percobaan paralel untuk N, P dan K dengan tingkat dosis pupuk berbeda menggunakan rancangan kelompok lengkap teracak sebanyak tiga ulangan. Dosis pupuk yang digunakan yaitu 0, 50, 100, 150, dan 200% dari acuan (100% N = 150 kg Urea ha-1, 100% P = 100 kg SP36 ha-1, 100% K = 100 kg KCl ha-1). Hasil dari peubah yang diamati dikonversi menjadi hasil relatif dan persamaan kuadrat dibuat untuk menentukan dosis pupuk N, P dan K optimum padi gogo Mayas, yaitu 174.79% N, 90.76% P2O5, dan 77.14% K2O dari acuan yang setara dengan 120.60 kg N, 32.67 kg P2O5, dan 46.28 kg K2O ha-1 atau 261.18 kg urea, 90.76 kg SP36, dan 77.14 kg KCl ha-1. Kata kunci: hasil relatif, multi nutrient response, dosis rekomendasi

PROBING THE COMPLEX INTERACTIONS BETWEEN DIET, DISEASE, AND AGING

Nutrient response pathways are conserved modifiers of longevity, and dietary restriction is the most studied intervention for slowing aging in laboratory animals. For many years it was believed that lifespan extension from dietary restriction was tightly linked to total caloric intake. Recent evidence suggests that the interaction between diet and aging is more complex than this, however, with nutrient sensing, dietary composition, and circadian components all playing a role. This symposium will delve into some of the complex biological interactions linking food intake, lifespan, and diseases of aging.