nitrogen starvation
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2021 ◽  
Author(s):  
Sofia Magkiriadou ◽  
Amanda Habel ◽  
Willi L. Stepp ◽  
Dianne K. Newman ◽  
Suliana Manley ◽  
...  

Polyphosphate (polyP) synthesis is a ubiquitous stress and starvation response in bacteria. In diverse species, mutants unable to make polyP have a wide variety of physiological defects, but the mechanisms by which this simple polyanion exerts its effects remain unclear. One possibility is that polyP′s many functions stem from global effects on the biophysical properties of the cell. We characterize the effect of polyphosphate on cytoplasmic mobility under nitrogen-starvation conditions in the opportunistic pathogen Pseudomonas aeruginosa. Using fluorescence microscopy and particle tracking, we characterize the motion of chromosomal loci and free tracer particles in the cytoplasm. In the absence of polyP and upon starvation, we observe an increase in mobility both for chromosomal loci and for tracer particles. Tracer particles reveal that polyP also modulates the partitioning between a ′more mobile′ and a ′less mobile′ population: small particles in cells unable to make polyP are more likely to be ′mobile′ and explore more of the cytoplasm, particularly during starvation. We speculate that this larger freedom of motion may be a consequence of nucleoid decompaction, which we also observe in starved cells deficient in polyP. Our observations suggest that polyP limits cytoplasmic mobility and accessibility during nitrogen starvation, which may help to explain the pleiotropic phenotypes observed in the absence of polyP.


2021 ◽  
Vol 12 ◽  
Author(s):  
Min Huang ◽  
Ju-Yuan Zhang ◽  
Xiaoli Zeng ◽  
Cheng-Cai Zhang

c-di-GMP is a ubiquitous bacterial signal regulating various physiological process. Anabaena PCC 7120 (Anabaena) is a filamentous cyanobacterium able to form regularly-spaced heterocysts for nitrogen fixation, in response to combined-nitrogen deprivation in 24h. Anabaena possesses 16 genes encoding proteins for c-di-GMP metabolism, and their functions are poorly characterized, except all2874 (cdgS) whose deletion causes a decrease in heterocyst frequency 48h after nitrogen starvation. We demonstrated here that c-di-GMP levels increased significantly in Anabaena after combined-nitrogen starvation. By inactivating each of the 16 genes, we found that the deletion of all1175 (cdgSH) led to an increase of heterocyst frequency 24h after nitrogen stepdown. A double mutant ΔcdgSHΔcdgS had an additive effect over the single mutants in regulating heterocyst frequency, indicating that the two genes acted at different time points for heterocyst spacing. Biochemical and genetic data further showed that the functions of CdgSH and CdgS in the setup or maintenance of heterocyst frequency depended on their opposing effects on the intracellular levels of c-di-GMP. Finally, we demonstrated that heterocyst differentiation was completely inhibited when c-di-GMP levels became too high or too low. Together, these results indicate that the homeostasis of c-di-GMP level is important for heterocyst differentiation in Anabaena.


2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Ang Li ◽  
Chirag Parsania ◽  
Kaeling Tan ◽  
Richard B. Todd ◽  
Koon Ho Wong

AbstractNutrient acquisition is essential for all organisms. Fungi regulate their metabolism according to environmental nutrient availability through elaborate transcription regulatory programs. In filamentous fungi, a highly conserved GATA transcription factor AreA and its co-repressor NmrA govern expression of genes involved in extracellular breakdown, uptake, and metabolism of nitrogen nutrients. Here, we show that the Aspergillus nidulans PnmB protease is a moonlighting protein with extracellular and intracellular functions for nitrogen acquisition and metabolism. PnmB serves not only as a secreted protease to degrade extracellular nutrients, but also as an intracellular protease to control the turnover of the co-repressor NmrA, accelerating AreA transcriptional activation upon nitrogen starvation. PnmB expression is controlled by AreA, which activates a positive feedback regulatory loop. Hence, we uncover a regulatory mechanism in the well-established controls determining the response to nitrogen starvation, revealing functional evolution of a protease gene for transcriptional regulation and extracellular nutrient breakdown.


2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Peerzada Yasir Yousuf ◽  
Peerzada Arshid Shabir ◽  
Khalid Rehman Hakeem

Nitrogen (N) is one of the indispensable nutrients required by plants for their growth, development, and survival. Being a limited nutrient, it is mostly supplied exogenously to the plants, to maintain quality and productivity. The increased use of N fertilizers is associated with high-cost inputs and negative environmental consequences, which necessitates the development of nitrogen-use-efficient plants for sustainable agriculture. Understanding the regulatory mechanisms underlying N metabolism in plants under low N is one of the prerequisites for the development of nitrogen-use-efficient plants. One of the important and recently discovered groups of regulatory molecules acting at the posttranscriptional and translational levels are microRNAs (miRNAs). miRNAs are known to play critical roles in the regulation of gene expression in plants under different stress conditions including N stress. Several classes of miRNAs associated with N metabolism have been identified so far. These nitrogen-responsive miRNAs may provide a platform for a better understanding of the regulation of N metabolism and pave a way for the development of genotypes for better N utilization. The current review presents a brief outline of miRNAs and their regulatory role in N metabolism.


2021 ◽  
Author(s):  
Daniel Jonathan Sher ◽  
Dikla Aharonovich ◽  
Osnat Weissberg

Interactions among microorganisms are ubiquitous, yet to what extent strain-level diversity affects interactions is unclear. Phototroph-heterotroph interactions in marine environments have been studied intensively, due to their potential impact on ocean ecosystems and biogeochemistry. Here, we characterize the interactions between five strains each of two globally abundant marine bacteria, Prochlorococcus (a phototroph) and Alteromonas (a heterotroph), from the first encounter between individual strains and over more than a year of subsequent co-culturing. Prochlorococcus-Alteromonas interactions affected primarily the dynamics of culture decline, which we interpret as representing cell mortality and lysis. The shape of the decline curve and the carrying capacity of the co-cultures were determined by the phototroph and not the heterotroph strains involved. Comparing various models of culture mortality suggests that death rate increases over time in mono-cultures but decreases in co-cultures, with cells potentially becoming more resistant to stress. During 435 days of co-culture, mutations accumulated in one Prochlorococcus strain (MIT9313) in genes involved in nitrogen metabolism and the stringent response, indicating that these processes occur during long-term nitrogen starvation. Our results suggest potential mechanisms involved in long-term starvation survival in co-culture, and highlight the information-rich growth and death curves as a useful readout of the interaction phenotype.


2021 ◽  
Vol 12 ◽  
Author(s):  
Lingxiao Zhu ◽  
Liantao Liu ◽  
Hongchun Sun ◽  
Yongjiang Zhang ◽  
Jijie Zhu ◽  
...  

Nitrogen (N) deficiency is one of the pivotal environmental factors that induce leaf senescence. However, little is known regarding the impact of low N on root senescence in cotton. Thus, the objective of this study was to investigate the effect of low nitrogen on root senescence. In this study, the molecular mechanism of cotton root senescence in response to nitrogen deficiency was investigated by combing physiological and transcriptomic analysis when no nitrogen and normal nitrogen (138mg N·kg−1 soil). The results showed that: (1) nitrogen starvation induced the premature senescence of leaf, while delaying root senescence. (2) The increase in catalase (CAT) activity at 60, 80, and 100days after emergence (DAE), combined with decrease of malonaldehyde content at 60, 80, and 100 DAE, and the content of abscisic acid (ABA), all of these contributed to the delay of root senescence by low nitrogen treatment. (3) To study the molecular mechanisms underlying root senescence, the gene expression profiling between low nitrogen and normal nitrogen treatments were compared pairwise at 20, 40, 60, 80, and 100 DAE. A total of 14,607 genes were identified to be differentially expressed at these five points. (5) Most genes involved in glutathione (GSH) and ascorbate peroxidase (APX) synthesis were upregulated, while ABA, apoptosis, caspase, and cell cycle-related differentially expressed genes (DEGs) were downregulated. Coupled with the physiology data, these results provide new insights into the effect of nitrogen starvation on root senescence.


2021 ◽  
Author(s):  
Minette Havenga ◽  
Brenda D. Wingfield ◽  
Michael J. Wingfield ◽  
Léanne L. Dreyer ◽  
Francois Roets ◽  
...  

Plants ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 2101
Author(s):  
Xingkang Li ◽  
Yuanmei Liang ◽  
Kai Li ◽  
Peng Jin ◽  
Jie Tang ◽  
...  

Both low temperature and nitrogen starvation caused chlorosis of cyanobacteria. Here, in this study, for the first time, we compared the effects of low temperature, nitrogen starvation, and their combination on the photosynthesis and metabolites of a thermophilic cyanobacterium strain, Thermosynechococcus E542. Under various culture conditions, the growth rates, pigment contents, and chlorophyll fluorescence were monitored, and the composition of alkanes, lipidomes, and carbohydrates were determined. It was found that low temperature (35 °C) significantly suppressed the growth of Thermosynechococcus E542. Nitrogen starvation at 45 °C and 55 °C did not affect the growth; however, combined treatment of low temperature and nitrogen starvation led to the lowest growth rate and biomass productivity. Both low temperature and nitrogen starvation caused significantly declined contents of pigments, but they resulted in a different effect on the OJIP curves, and their combination led to the lowest pigment contents. The composition of fatty acids and alkanes was altered upon low-temperature cultivation, while nitrogen starvation caused reduced contents of all lipids. The low temperature did not affect carbohydrate contents, while nitrogen starvation greatly enhanced carbohydrate content, and their combination did not enhance carbohydrate content, but led to reduced productivity. These results revealed the influence of low temperature, nitrogen starvation, and their combined treatment for the accumulation of phycobiliproteins, lipids, and carbohydrates of a thermophilic cyanobacterium strain, Thermosynechococcus E542.


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