Genetics studies the structure/function of genes via the characterization of their mutant phenotypes. In plants, a readily scorable mutant phenotype comprises macroscopic lesions symptomatic of ...disease in the absence of pathogens. Such mutants therefore exhibit autoimmune phenotypes. Many of these mutants are considered to be associated with immunity and the corresponding genes have been described as ‘negative regulators’ of immunity and/or cell death. Pathogens deliver effectors into host cells to increase infectivity by modifying or removing host proteins. Plants detect effectors via nucleotide‐binding, leucine‐rich repeat (NLR) immune receptors, which monitor host effector targets. In response to effector‐mediated target tampering, NLR proteins potentiate immunity. The guard hypothesis proposes that NLRs ‘guard’ host ‘guardees’ targeted by pathogen effectors. An obvious corollary to this guard model is that forms of plant autoimmunity are a result of inappropriate NLR protein activation. In this review, we discuss what is known about some of the ‘negative regulators’ of immunity, and propose simple strategies that may help to characterize autoimmune mutants.
In plants, pathogenic effectors target host proteins to establish infection. Plant NLR immune receptors detect effector modifications on host targets and trigger immunity. Not surprisingly, a corollary is that mutations in effector targets can cause NLR triggered autoimmunity.
Somatic cells acclimate to changes in the environment by temporary reprogramming. Much has been learned about transcription factors that induce these cell‐state switches in both plants and animals, ...but how cells rapidly modulate their proteome remains elusive. Here, we show rapid induction of autophagy during temporary reprogramming in plants triggered by phytohormones, immune, and danger signals. Quantitative proteomics following sequential reprogramming revealed that autophagy is required for timely decay of previous cellular states and for tweaking the proteome to acclimate to the new conditions. Signatures of previous cellular programs thus persist in autophagy‐deficient cells, affecting cellular decision‐making. Concordantly, autophagy‐deficient cells fail to acclimatize to dynamic climate changes. Similarly, they have defects in dedifferentiating into pluripotent stem cells, and redifferentiation during organogenesis. These observations indicate that autophagy mediates cell‐state switches that underlie somatic cell reprogramming in plants and possibly other organisms, and thereby promotes phenotypic plasticity.
Synopsis
Adjustment to new environmental signals requires temporary and rapid modulation of the cellular proteome. Proteome adjustments are found to require autophagy, which erases previous cellular states in plant somatic cells to allow new programs to unfold.
Multiple external stimuli rapidly activate autophagy in plant cells.
Proteome adjustments during cell‐state switching are disrupted in autophagy mutants.
Autophagy‐deficient plants exhibit decreased phenotypic plasticity.
Autophagy‐deficient somatic cells cannot de‐differentiate efficiently into pluripotent stem cells.
Exit from pluripotency and organ formation are dysregulated in autophagy‐deficient cells.
Autophagy facilitates cellular proteome adjustment to new stimuli and allows coordinated transition to a new cell state by erasing previous cellular programs.
Animal and plant somatic cells have the capacity to switch states or reprogram into stem cells to adapt during stress and injury. This ability to deal with stochastic changes or reprogramming of ...somatic cells also needs macroautophagy/autophagy. Here, we expand on this notion and provide a primary example of how overexpression of ATG8/LC3 in the moss Physcomitrium patens enhances the ability to reprogram somatic cells into stem cells when subjected to severe wounding. This observation suggests that autophagy is not only required for cells to dedifferentiate but also makes cells more competent to do so.
Abbreviations: ATG: autophagy related; atg5: AUTOPHAGY 5; ATG8/LC3: AUTOPHAGY 8/microtubule associated protein 1 light chain 3; GFP: green fluorescent protein
To establish infection, pathogens deploy effectors to modify or remove host proteins. Plant immune receptors with nucleotide-binding, leucine-rich repeat domains (NLRs) detect these modifications and ...trigger immunity. Plant NLRs thus guard host “guardees.” A corollary is that autoimmunity may result from inappropriate NLR activation because mutations in plant guardees could trigger corresponding NLR guards. To explore these hypotheses, we expressed 108 dominant-negative (DN) Arabidopsis NLRs in various lesion mimic mutants, including camta3, which exhibits autoimmunity. CAMTA3 was previously described as a negative regulator of immunity, and we find that autoimmunity in camta3 is fully suppressed by expressing DNs of two NLRs, DSC1 and DSC2. Additionally, expression of either NLR triggers cell death that can be suppressed by CAMTA3 expression. These findings support a model in which DSC1 and DSC2 guard CAMTA3, and they suggest that other negative regulators of immunity may similarly represent guardees.
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•Dominant-negative NLR forms (DN-NLR) disrupt the function of wild-type NLR alleles•DN-NLRs can be used to screen for suppression of autoimmunity in autoimmune mutants•Two NLRs (DSC1 and DSC2) are responsible for autoimmunity in Arabidopsis camta3 mutants•Immunity triggered by DSC1 or DSC2 in tobacco is suppressed by CAMTA3 co-expression
NLRs detect pathogen-induced modifications in plant proteins, triggering immunity. Lolle et al. express dominant-negative NLRs (DN-NLRs) and screen for suppressed autoimmunity in various mutants. DN-NLRs for DSC1 and DSC2 suppress autoimmunity in a camta3 mutant, a putative negative regulator of immunity, suggesting that autoimmunity results from detection of modified self.
DNA damage observed during plant immune responses is reported to be an intrinsic component of plant immunity. However, other immune responses may suppress DNA damage to maintain host genome ...integrity. Here, we show that immunity-related DNA damage can be abrogated by preventing cell death triggered by Nucleotide-binding, Leucine-rich-repeat immune Receptors (NLRs). SNI1 (suppressor of npr1-1, inducible 1), a subunit of the structural maintenance of chromosome (SMC) 5/6 complex, was reported to be a negative regulator of systemic acquired resistance (SAR) and to be necessary for controlling DNA damage. We find that cell death and DNA damage in sni1 loss-of-function mutants are prevented by mutations in the NLR signaling component EDS1. Similar to sni1, elevated DNA damage is seen in other autoimmune mutants with cell death lesions, including camta3, pub13 and vad1, but not in dnd1, an autoimmune mutant with no visible cell death. We find that as in sni1, DNA damage in camta3 is EDS1-dependent, but that it is also NLR-dependent. Using the NLR RPM1 as a model, we also show that extensive DNA damage is observed when an NLR is directly triggered by effectors. We also find that the expression of DNA damage repair (DDR) genes in mutants with cell death lesions is down regulated, suggesting that degraded DNA that accumulates during cell death is a result of cellular dismantling and is not sensed as damaged DNA that calls for repair. Our observations also indicate that SNI1 is not directly involved in SAR or DNA damage accumulation.
The present work is related to the treatment of crushed waste of printed circuit boards (WPCBs) from electrical and electronic devices (WEEE), carrying out the recovery of copper in solution. In the ...first stage, the studied material was characterized by AAS, SEM-EDS, and XRD. The results revealed significantly high amounts of copper (744.42 mg/g), compared with the rest of the metals present in the sample, mainly iron and zinc. In the second stage of the work, alkali dynamic leaching experiments were carried out in the S2O3−2− O2 medium, evaluating important kinetic variables in order to verify the controlling step of the system and adjust the data to a kinetic model. According to the results obtained from the various experimental tests executed, it was found that in the studied system of S2O3−2− O2, the leaching of copper was preferably adjusted to the model of spherical particles with a shrinking core finding a mixed chemical−diffusive control, with values of Ea = 25.78 kJ/mol and n = 0.22 (for the leaching reagent), indicating that the reaction was controlled by the oxygen transport to the solid−liquid interface and also by the chemical reaction in the surface of particles, obtaining up to 99.82% copper in solution.
Due to the significant growth of the world population, the accelerated growth of economic industries in various countries, and improved living conditions, freshwater consumption has increased ...dramatically and is currently under critical pressure. Its good use and rationing are essential. Even though mining is an industry that consumes much less water than other industries, such as agriculture, surrounding communities are constantly questioned. This occurs mainly because mining deposits are generally found in arid areas where freshwater is scarce, forcing government authorities to regulate water use in mining processes more severely. Faced with this scenario, the mining industry has innovated the use of seawater and wastewater from processes for its production processes. In addition, various projects are under development to construct desalination plants and water impulsion systems of the sea; therefore, it is expected that seawater and/or wastewater in mining will continue to grow in the coming years. Among the main challenges faced in the use of these water resources in mining is: (i) the close relationship that exists between the use of seawater and energy consumption, transferring the problem of water scarcity to a problem of energy cost overruns; (ii) generation of greater integration between the use of water and sustainable energy; and (iii) brine management is economically expensive and technically challenging and, therefore, most desalination plants discharge untreated brine directly into the sea, causing an environmental impact. On the other hand, regarding the use of these water resources in leaching processes, there are very positive results for the dissolution of copper from sulfide minerals, where the wastewater from desalination plants presents better results than seawater due to its higher concentration of chloride ions, allowing it to work at higher redox potential values in order to increase copper dissolution. This manuscript is a bibliographic review in which finally, it is concluded that it is feasible to incorporate wastewater from water desalination plants in heap leaching processes for copper sulfide ores, as long as the cost of transfer from water desalination plants to mining sites can be supported.
Artificial intelligence and machine learning algorithms have an increasingly pervasive presence in all fields of science due to their ability to find patterns, model dynamic systems, and make ...predictions of complex processes. This review aims at providing the researchers in the mineral processing area with structured knowledge about the applications of machine learning algorithms to the leaching process, showing the applications of techniques such as artificial neural networks (ANN), support vector machines (SVM), or Bayesian networks (BN), among others. Additionally, future perspectives are indicated, emphasizing both the generalization of the algorithms and the productive potential of the application of modeling, simulation, and optimization of the tools studied to industrial processes.
• Background and Aims DNA flow cytometry requires preparation of suspensions of intact nuclei, which are stained using a DNA-specific fluorochrome prior to analysis. Various buffer formulas were ...developed to preserve nuclear integrity, protect DNA from degradation and facilitate its stoichiometric staining. Although nuclear isolation buffers differ considerably in chemical composition, no systematic comparison of their performance has been made until now. This knowledge is required to select the appropriate buffer for a given species and tissue. • Methods Four common lysis buffers (Galbraith's, LB01, Otto's and Tris.MgCl2) were used to prepare samples from leaf tissues of seven plant species (Sedum burrito, Oxalis pes-caprae, Lycopersicon esculentum, Celtis australis, Pisum sativum, Festuca rothmaleri and Vicia faba). The species were selected to cover a wide range of genome sizes (1·30–26·90 pg per 2C DNA) and a variety of leaf tissue types. The following parameters were assessed: forward (FS) and side (SS) light scatters, fluorescence of propidium iodide-stained nuclei, coefficient of variation of DNA peaks, presence of debris background and the number of nuclei released from sample tissue. The experiments were performed independently by two operators and repeated on three different days. • Key Results Clear differences among buffers were observed. With the exception of O. pes-caprae, any buffer provided acceptable results for all species. LB01 and Otto's were generally the best buffers, with Otto's buffer providing better results in species with low DNA content. Galbraith's buffer led to satisfactory results and Tris.MgCl2 was generally the worst, although it yielded the best histograms in C. australis. A combined analysis of FS and SS provided a ‘fingerprint’ for each buffer. The variation between days was more significant than the variation between operators. • Conclusions Each lysis buffer tested responded to a specific problem differently and none of the buffers worked best with all species. These results expand our knowledge on nuclear isolation buffers and will facilitate selection of the most appropriate buffer depending on species, tissue type and the presence of cytosolic compounds interfering with DNA staining.
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