Poplar (
spp.) is a valuable tree species with multiple applications in afforestation. However, its growth in saline areas, including coastal regions, is limited. This study aimed to investigate the ...physiological mechanisms of arbuscular mycorrhizal fungi (AMF) symbiosis with 84K (
) poplar under salt stress. We conducted pot experiments using NaCl solutions of 0 mM (control), 100 mM (moderate stress), and 200 mM (severe stress) and evaluated the colonization of AMF and various physiological parameters of plants, including photosynthesis, biomass, antioxidant enzyme activity, nutrients, and ion concentration. Partial least squares path modeling (PLS-PM) was employed to elucidate how AMF can improve salt tolerance in poplar. The results demonstrated that AMF successfully colonized the roots of plants under salt stress, effectively alleviated water loss by increasing the transpiration rate, and significantly enhanced the biomass of poplar seedlings. Mycorrhiza reduced proline and malondialdehyde accumulation while enhancing the activity of antioxidant enzymes, thus improving plasma membrane stability. Additionally, AMF mitigated Na
accumulation in plants, contributing to the maintenance of a favorable ion balance. These findings highlight the effectiveness of using suitable AMF to improve conditions for economically significant tree species in salt-affected areas, thereby promoting their utilization.
Cell growth is a complex process in which cells synthesize cellular components while they increase in size. It is generally assumed that the rate of biosynthesis must somehow be coordinated with the ...rate of growth in order to maintain intracellular concentrations. However, little is known about potential feedback mechanisms that could achieve proteome homeostasis or the consequences when this homeostasis is perturbed. Here, we identify conditions in which fission yeast cells are prevented from volume expansion but nevertheless continue to synthesize biomass, leading to general accumulation of proteins and increased cytoplasmic density. Upon removal of these perturbations, this biomass accumulation drove cells to undergo a multi-generational period of “supergrowth” wherein rapid volume growth outpaced biosynthesis, returning proteome concentrations back to normal within hours. These findings demonstrate a mechanism for global proteome homeostasis based on modulation of volume growth and dilution.
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•Cell growth involves balance between rates of volume growth and protein synthesis•Inhibition of volume growth leads to an increase in global protein density•Increased density drives accelerated growth after release from growth inhibition•Accelerated growth serves as a homeostatic mechanism to dilute excess protein
During cell growth, rates of protein synthesis and cellular expansion must somehow be coordinated to maintain global protein concentrations. We find in fission yeast cells that upon inhibition of volume growth, protein biosynthesis nevertheless continues, leading to global accumulation of proteins and increased cellular density. Upon release of growth inhibition, cells exhibit abnormally accelerated growth (supergrowth), which dilutes the excess protein. These phenomena demonstrate a proteome homeostasis mechanism based upon cell growth regulation.
The mechanisms ensuring specific incorporation of CENP-A at centromeres are poorly understood. Mis16 and Mis18 are required for CENP-A localization at centromeres and form a complex that is conserved ...from fission yeast to human. Fission yeast sim1 mutants that alleviate kinetochore domain silencing are defective in Scm3Sp, the ortholog of budding yeast Scm3Sc. Scm3Sp depends on Mis16/18 for its centromere localization and like them is recruited to centromeres in late anaphase. Importantly, Scm3Sp coaffinity purifies with CENP-ACnp1 and associates with CENP-ACnp1 in vitro, yet localizes independently of intact CENP-ACnp1 chromatin and is differentially released from chromatin. While Scm3Sc has been proposed to form a unique hexameric nucleosome with CENP-ACse4 and histone H4 at budding yeast point centromeres, we favor a model in which Scm3Sp acts as a CENP-ACnp1 receptor/assembly factor, cooperating with Mis16 and Mis18 to receive CENP-ACnp1 from the Sim3 escort and mediate assembly of CENP-ACnp1 into subkinetochore chromatin.
The fidelity of epigenetic inheritance or, the precision by which epigenetic information is passed along, is an essential parameter for measuring the effectiveness of the process. How the precision ...of the process is achieved or modulated, however, remains largely elusive. We have performed quantitative measurement of epigenetic fidelity, using position effect variegation (PEV) in Schizosaccharomyces pombe as readout, to explore whether replication perturbation affects nucleosome-mediated epigenetic inheritance. We show that replication stresses, due to either hydroxyurea treatment or various forms of genetic lesions of the replication machinery, reduce the inheritance accuracy of CENP-A/Cnp1 nucleosome positioning within centromere. Mechanistically, we demonstrate that excessive formation of single-stranded DNA, a common molecular abnormality under these conditions, might have correlation with the reduction in fidelity of centromeric chromatin duplication. Furthermore, we show that replication stress broadly changes chromatin structure at various loci in the genome, such as telomere heterochromatin expanding and mating type locus heterochromatin spreading out of the boundaries. Interestingly, the levels of inheritable expanding at sub-telomeric heterochromatin regions are highly variable among independent cell populations. Finally, we show that HU treatment of the multi-cellular organisms C. elegans and D. melanogaster affects epigenetically programmed development and PEV, illustrating the evolutionary conservation of the phenomenon. Replication stress, in addition to its demonstrated role in genetic instability, promotes variable epigenetic instability throughout the epigenome.
Cordycepin, which has great immunomodulatory activities such as anticancer, antifungal, antivirus, antileukemia and lipid-lowering ones, is the secondary metabolite of Cordyceps militaris (C. ...militaris). Liquid submerged fermentation is the common cultivation process to produce cordycepin. To optimize the fermentation process and improve production, monitoring the cordycepin secretion in the fermentation is essential. The measurement based on chromatography-mass spectrometry methods is generally involved in the complex sample pretreatments and time-consuming separation, so more rapid and convenient methods are required. Matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) is more attractive for faster and direct detection. Therefore, MALDI-MS detection combined with isotope-labeled internal standard was applied to the measurement of cordycepin content in the fermentation broth and mycelium. This method made accurate quantification of cordycepin in the range of 5–400 μg/mL with a relative standard deviation of 5.6%. The recovery rates of fermentation samples after the 1, 13, and 25 days were 90.15%, 94.27%, and 95.06%, respectively. The contents of cordycepin in the mycelium and fermentation broth were 136 mg/g and 148.39 mg/mL on the 20th culture day, respectively. The cordycepin secretion curve of the liquid fermentation of C. militaris was real-time traced over 25 days.
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•A rapid quantification method of cordycepin based on MALDI-MS is proposed.•The quantification relies on the stable isotope standard method.•Rapid determination of the cordycepin content in the liquid fermentation broth of Cordyceps militaris without pre-treatment.•Monitoring the fermentation state of C. militaris fermentation broth is benefit to improve the yield of cordycepin.
Point and regional centromeres specify a unique site on each chromosome for kinetochore assembly. The point centromere in budding yeast is a unique 150-bp DNA sequence, which supports a kinetochore ...with only one microtubule attachment. In contrast, regional centromeres are complex in architecture, can be up to 5 Mb in length, and typically support many kinetochore-microtubule attachments. We used quantitative fluorescence microscopy to count the number of core structural kinetochore protein complexes at the regional centromeres in fission yeast and Candida albicans. We find that the number of CENP-A nucleosomes at these centromeres reflects the number of kinetochore-microtubule attachments instead of their length. The numbers of kinetochore protein complexes per microtubule attachment are nearly identical to the numbers in a budding yeast kinetochore. These findings reveal that kinetochores with multiple microtubule attachments are mainly built by repeating a conserved structural subunit that is equivalent to a single microtubule attachment site.
Ribosomes within a cell are commonly viewed as biochemically homogenous RNA–protein super-complexes performing identical functions of protein synthesis. However, recent evidence suggests that ...ribosomes may be a more dynamic macromolecular complex with specialized roles. Here, we present extensive genetic and molecular evidence in the fission yeast S. pombe that the paralogous genes for many ribosomal proteins (RPs) are functionally different, despite that they encode the same ribosomal component, often with only subtle differences in the sequences. Focusing on the rps8 paralog gene deletions rps801d and rps802d, we showed that the mutant cells differ in the level of Rpl42p in actively translating ribosomes and that their phenotypic differences reside in the Rpl42p level variation instead of the subtle protein sequence difference between Rps801p and Rps802p. Additional 40S ribosomal protein paralog pairs also exhibit similar phenotypic differences via differential Rpl42p levels in actively translating ribosomes. Together, our work identifies variations in the Rpl42p level as a potential form of ribosome heterogeneity in biochemical compositions and suggests a possible connection between large and small subunits during ribosome biogenesis that may cause such heterogeneity. Additionally, it illustrates the complexity of the underlying mechanisms for the genetic specificity of ribosome paralogs.
•UPLC-MS/MS and GC × GC-TOF/MS based metabolomics was applied to morel.•253 non-VOCs and 87 VOCs were differentially accumulated between two cultivars of morel.•Variations in lipids, carbohydrates, ...amino acids, alcohols and ketones cause flavor difference.•Morchella importuna showed more mushroom flavor and sweeter flavor than Morchella sextelata.
Morchella sextelata and Morchella importuna are the main cultivars of morel. However, the key compounds affecting their flavors (taste and odor) are currently unknown. Here, an ultra performance tandem mass spectrometry combined with two-dimensional gas chromatography-time-of-flight mass spectrometry method was used to detect and relatively quantify the metabolites in both morel cultivars. A total of 631 non-volatile compounds and 242 volatile compounds were identified. The odor activity value was calculated to assess the contribution of key odor volatile. The results indicated that M. importuna had a sweeter flavor than M. sextelata. The former posed more prominent mushroom flavor than the latter based on the correlation analysis of the metabolites. The flavor differences of the two morel cultivars are highly relevant with the content of lipids, carbohydrates, amino acids and derivatives, alcohols and ketones. This study provides new insights into the theoretical basis for the flavor differences in both morel cultivars.
The accurate segregation of chromosomes at mitosis requires that all pairs of chromatids bind correctly to microtubules prior to the dissolution of sister cohesion and the initiation of anaphase. By ...analyzing the motion of GFP-tagged S. cerevisiae chromosomes, we show that kinetochore-microtubule attachments impose sufficient tension on sisters during prometaphase to transiently separate centromeric chromatin toward opposite sides of the spindle. Transient separations of 2–10 min duration occur in the absence of cohesin proteolysis, are characterized by independent motion of the sisters along the spindle, and are followed by the apparent reestablishment of sister linkages. The existence of transient sister separation in yeast explains the unusual bilobed localization of kinetochore proteins and supports an alternative model for spindle structure. By analogy with animal cells, we propose that yeast centromeric chromatin acts as a tensiometer.
Reversible phosphorylation has emerged as an important mechanism for regulating proteasome function in various physiological processes. Essentially all proteasome phosphorylations characterized thus ...far occur on proteasome holoenzyme or subcomplexes to regulate substrate degradation. Here, we report a highly conserved phosphorylation that only exists on the unassembled α5 subunit of the proteasome. The modified residue, α5-Ser16, is within a SP motif typically recognized by cyclin-dependent kinases (CDKs). Using a phospho-specific antibody generated against this site, we found that α5-S16 phosphorylation is mitosis-specific in both yeast and mammalian cells. Blocking this site with a S16A mutation caused growth defect and G2/M arrest of the cell cycle. α5-S16 phosphorylation depends on CDK1 activity and is highly abundant in some but not all mitotic cells. Immunoprecipitation and mass spectrometry (IP-MS) studies identified numerous proteins that could interact with phosphorylated α5, including PLK1, a key regulator of mitosis. α5-PLK1 interaction increased upon mitosis and could be facilitated by S16 phosphorylation. CDK1 activation downstream of PLK1 activity was delayed in S16A mutant cells, suggesting an important role of α5-S16 phosphorylation in regulating PLK1 and mitosis. These data have revealed an unappreciated function of "exo-proteasome" phosphorylation of a proteasome subunit and may bring new insights to our understanding of cell cycle control.
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