Search Results (47)

The transcription factor Pho4 is crucial for the response to phosphate starvation in many fungi, and it has been linked to tolerance to alkalinization of the medium and to pathogenicity. It is widely accepted that it is encoded by a single gene. However, the industrially relevant yeast Komagataella phaffii might contain two Pho4-encoding genes (PAS_chr1-1_0265 and PAS_chr2-1_0177, designated here PHO4(A) and PHO4(B), respectively), which have never been functionally characterized. The phenotypic analysis of single and double mutants suggests that Pho4(B) plays a major role in the adaptation to Pi scarcity. While single mutants exhibited limited and non-overlapping phenotypic defects, the pho4(A) pho4(B) strain was sensitive to multiple types of stress, including phosphate starvation and alkaline pH. Transcriptomic analysis confirms that Pho4(B) is crucial for the transcriptional response to phosphate starvation, including induction of typical gene markers (PHO5, PHO89, VTC1, etc.). However, by using a GFP reporter, we found that PHO4(A) also participates in the induction of PHO89 under high pH stress. Expression of both PHO4(A) and PHO4(B) in Saccharomyces cerevisiae complemented the pho4 mutation under phosphate limitation by restoring growth, expression of the Pho84 transporter, and secreted phosphatase activity. Therefore, both transcription factors display partially overlapping functions, respond differently to diverse stimuli, and together constitute a key component in the adaptation to multiple stresses. Full article

Phosphorus (Pi) deficiency limits plant productivity. Light quality modulates growth and stress responses, but its interaction with Pi starvation in banana is unclear. We investigated physiological, transcriptomic, and metabolomic responses of banana seedlings to low Pi under white (WL), red (R), far-red (FR), blue (B), and ultraviolet (UV-A) light. FR light promoted shoot elongation and increased phosphorus, iron, and calcium accumulation, whereas B and UV-A exacerbated growth inhibition and oxidative stress (higher H₂O₂, MDA, and proline). Transcriptomics revealed that B and UV-A enriched cell cycle and stress pathways, while FR enriched photosynthesis and cell wall biogenesis. Expression of phosphate transporters and starvation-responsive genes was spectrum-specific. Metabolomics showed B and UV-A triggered massive accumulation of ABA, flavonoids, and secondary metabolites, indicating strong stress defense. Antioxidant enzyme activities were differentially activated: B upregulated SOD, CAT, and POD; UV specifically enhanced GSH-Px. Integrated correlation networks revealed distinct regulatory hubs: blue light centered on ROS scavenging, red light on phosphate transport. Our findings demonstrate that FR light acts as a positive regulator, while B and UV-A act as additional stressors under Pi deficiency, providing a mechanistic framework for using light spectra to improve crop resilience in Pi-limited conditions. Full article

Background/Objectives: MYC-driven tumors exhibit significant glutamine addiction, but the metabolic adaptation mechanisms enabling their survival under glutamine deprivation remain incompletely understood. Malic enzymes catalyze the oxidative decarboxylation of malate to pyruvate while generating NADPH, linking central carbon metabolism to redox homeostasis. This study investigates whether and how ME1 and ME2 mediate cell adaptation to glutamine starvation and explores their functional division in relation to p53 status. Methods: Using MYC-amplified, p53-mutant (G266E) SF188 glioblastoma cells, we performed siRNA-mediated knockdown, overexpression, and rescue experiments. Cell survival was assessed by trypan blue exclusion and Annexin V/PI staining. ROS levels and NADP⁺/NADPH ratios were measured by DCFH-DA fluorescence and enzymatic assays. Metabolite tracing was conducted using [U-¹³C₅] glutamine followed by LC-MS. Key findings were validated in additional cell lines including HCT116, U2OS and MDA-MB-231. Results: ME1 and ME2 promote SF188 cell survival under glutamine deprivation, an effect that depends on their catalytic activity but is independent of TCA cycle anaplerosis. ME1 maintains redox balance by generating NADPH, and antioxidant treatment rescues the survival defect caused by ME1 knockdown. In contrast, ME2 does not contribute to redox regulation but stabilizes mutant p53 (G266E) via proteasome inhibition. Both of these pro-survival functions are attenuated upon MYC knockdown, suggesting a dependency on MYC expression. Across all cell lines tested, ME1 and ME2 also promote survival through redox maintenance, although the isoform responsible for antioxidant function differs. Conclusions: ME1 and ME2 support metabolic adaptation to glutamine starvation through distinct, isoform-specific mechanisms that depend on MYC expression and p53 mutation status. These findings suggest malic enzymes as potential therapeutic targets in MYC-driven, p53-mutant tumors. Full article

Phosphorus deficiency in the environment induces phosphate (Pi) starvation responses of plants, in which the phosphate transporter is one of the most critical functional genes in this response mechanism. As a prevalent green manure crop in China, Vicia villosa plays a critical role in sustainable agricultural systems, and the expression of its phosphate transporter gene (VvPHT1) is modulated by soil phosphorus availability, highlighting its key adaptive function in nutrient acquisition and utilization under low-Pi conditions. Functional studies of this gene and its promoter contribute to exploring the molecular mechanisms of the tolerance of green manure crops to low phosphorus stress and to improving phosphorus-efficient V. villosa varieties. In this study, analysis of the VvPHT1 promoter sequence revealed a 1524 bp region containing multiple root-specific cis-regulatory elements, including five NODCON2GM, one NODCON1GM, six OSE2ROOTNODULE, one OSE1ROOTNODULE, and fifteen ROOTMOTIFTAPOX1 motifs. Histochemical GUS staining of transgenic Arabidopsis (Arabidopsis thaliana (L.) Heynh.) showed that the VvPHT1 promoter directed root-specific expression of the GUS reporter gene. A fusion expression vector pCAMBIA1300-VvPHT1--GFP was constructed and transformed into tobacco (Nicotiana tabacum L.) cells for subcellular localization analysis, indicating that the protein encoded by VvPHT1 was localized to the plasma membrane. To quantify its expression, VvPHT1 transcript levels in VvPHT1-overexpressing Arabidopsis (OEPHT1) lines were analyzed by quantitative real-time PCR (qRT-PCR) under different phosphorus supply conditions. The results demonstrated that under low-Pi conditions, the expression of VvPHT1 was significantly upregulated in the OEPHT1 lines compared to those of normal-Pi conditions. Furthermore, under low-Pi treatment, the OEPHT1 lines showed significantly increased fresh weight, primary root length, phosphorus content, and chlorophyll content compared to the wild-type Arabidopsis (WT), while no such differences were observed under normal-Pi conditions. In conclusion, the VvPHT1 promoter exhibits root-specific activity, and the VvPHT1 gene encodes a plasma-membrane-localized phosphate transporter that is strongly induced by phosphorus deficiency. Its overexpression enhances phosphorus uptake and plant growth under low-Pi conditions, suggesting that VvPHT1 likely functions as a high-affinity phosphate transporter involved in the adaptation to phosphorus starvation. Full article

Phosphorus is a fundamental macronutrient, yet its low bioavailability in most soils makes phosphorus deficiency one of the most persistent constraints limiting global crop productivity. Although mineral fertilisation has long been the primary strategy for maintaining adequate P supply, inefficient fertiliser use and strong soil phosphorus fixation result in substantial losses. As a result, current research is shifting toward integrated phosphorus management approaches that combine optimised fertilisation techniques, unconventional phosphorus sources, and biological tools that mobilise soil-bound phosphorus. At the same time, silicon has emerged as a promising modulator of plant stress resilience, which can also influence phosphorus homeostasis. Silicon enhances plant physiological robustness by strengthening tissues, improving photosynthetic performance, and activating antioxidant pathways. Silicon may also modify phosphorus mobility in soils, promoting more efficient uptake and utilisation in plant tissues. This review synthesises current knowledge on physiological and molecular plant responses to phosphorus deficiency. It compares modern fertilisation strategies, ranging from precision fertilisation to unconventional phosphorus fertilisers. Particular attention is devoted to the emerging role of silicon in improving phosphorus availability and in enhancing crop plant phosphorus-use efficiency. The review concludes with future research directions that may help integrate silicon-based interventions into sustainable nutrient-management systems. Full article

Apyrase (nucleotide triphosphate diphosphohydrolase, NTPDase; EC 3.6.1.5) functions in a variety of plant growth and developmental processes, as well as responses to pathogens, in part, by regulating extracellular ATP (eATP) concentrations. In this study, we investigated potential roles of apyrase in the recruitment of phosphate (Pi) from extracellular nucleotides in Arabidopsis thaliana seedlings that constitutively overexpress apyrase 1 (APY1). Under Pi limitation, both WT and APY1 seedlings had decreased Pi contents and a characteristic remodeling of root system architecture (RSA). This phosphate starvation response (PSR) was prevented by the uptake of Pi released through the metabolism of extracellular NTP, which occurred at a higher rate in APY1 seedlings. APY1 seedlings had higher Pi contents than WT seedlings on Pi-sufficient media supplemented with NTP and exhibited markedly increased LR and root hair (RH) formation. Genome-wide expression profiling revealed that this expanded RSA of APY1 seedlings was correlated with the induction of >100 genes involved in regulation of auxin homeostasis, signaling, and transport, which previous studies have shown to be increased when APY1 is overexpressed. APY1 regulation of [eNTP] and purinergic signaling may thus contribute to modulation of auxin responses, resulting in enhanced uptake of Pi from the medium, including Pi released via eNTP metabolism. Full article

Phosphorus, as an essential nutrient, plays an important role in plant growth and development. Although Phosphate Starvation Response 1 (PHR1) or PHR1-like have been recognized as central regulators of phosphorus (Pi) homeostasis in several plants, they have not been systematically studied in Cucurbitaceae. In this study, 11, 10, 8, 12, 12, and 22 PHR genes were identified in cucumber, melon, bottle gourd, watermelon, wax gourd, and pumpkin, respectively, by genome-wide analysis. Phylogenetic analysis showed that the Cucurbitaceae PHR genes were divided into seven distinct subfamilies. These genes were further phylogenetically analyzed for their chromosomal localization, gene structure, protein structure, and synteny. Genomic homology analysis showed that many PHR genes existed in the corresponding homology blocks of six Cucurbitaceae species. qRT-PCR analysis showed that the CmoPHR genes exhibited differential expression under different concentrations of phosphate treatment. Transcriptional self-activation assays showed that CmoPHR2, CmoPHR9, CmoPHR16, and CmoPHR17 proteins had transcriptional self-activating activity. The results of this study provide a basis for the further cloning and functional validation of genes related to the phosphate regulatory network in pumpkin. Full article

The phosphate starvation response (PHR) transcription factor family play central regulatory roles in nutrient signaling, but its relationship with other abiotic stress remains elusive. In the woody plant Eucalyptus grandis, we characterized 12 EgPHRs, which were phylogenetically divided into three groups, with group I exhibiting conserved structural features (e.g., unique motif composition and exon number). Notably, a protein–protein interaction network analysis revealed that EgPHR had a species-specific protein–protein interaction network: EgPHR6 interacted with SPX proteins of multiple species, while Eucalyptus and poplar PHR uniquely bound to TRARAC-kinesin ATPase, suggesting functional differences between woody and herbaceous plants. A promoter sequence analysis revealed a regulatory network of 59 transcription factors (TFs, e.g., BPC, MYBs, ERFs and WUS), mainly associated with tissue differentiation, abiotic stress, and hormonal responses that regulated EgPHRs’ expression. Transcriptomics and RT-qPCR gene expression analyses showed that all EgPHRs dynamically responded to phosphate (Pi) starvation, with the expression of EgPHR2 and EgPHR6 exhibiting sustained induction, and were also regulated by salt, cold, jasmonic acid, and boron deficiency. Strikingly, nitrogen starvation suppressed most EgPHRs, highlighting crosstalk between nutrient signaling pathways. These findings revealed the multifaceted regulatory role of EgPHRs in adaptation to abiotic stresses and provided insights into their unique evolutionary and functional characteristics in woody plants. Full article

Penicillium italicum, a major postharvest pathogen, causes blue mold rot in citrus fruits through the deployment of various virulence factors. Recent studies highlight the role of the epigenetic reader, SntB, in modulating the pathogenicity of phytopathogenic fungi. Our research revealed that the deletion of the SntB gene in P. italicum led to significant phenotypic alterations, including delayed mycelial growth, reduced spore production, and decreased utilization of sucrose. Additionally, the mutant strain exhibited increased sensitivity to pH fluctuations and elevated iron and calcium ion stress, culminating in reduced virulence on Gannan Novel oranges. Ultrastructural analyses disclosed notable disruptions in cell membrane integrity, disorganization within the cellular matrix, and signs of autophagy. Transcriptomic data further indicated a pronounced upregulation of hydrolytic enzymes, oxidoreductases, and transport proteins, suggesting a heightened energy demand. The observed phenomena were consistent with a carbon starvation response potentially triggering apoptotic pathways, including iron-dependent cell death. These findings collectively underscored the pivotal role of SntB in maintaining the pathogenic traits of P. italicum, proposing that targeting PiSntB could offer a new avenue for controlling citrus fungal infections and subsequent fruit decay. Full article

Inorganic phosphate (Pi) homeostasis plays an important role in plant growth and abiotic stress tolerance. Several MYB-CC transcription factors involved in Pi homeostasis have been identified in rice (Oryza sativa). PHOSPHATE STARVATION RESPONSE-LIKE 7 (PHL7) is a class II MYC-CC protein, in which the MYC-CC domain is located at the N terminus. In this study, we established that OsPHL7 is localized to the nucleus and that the encoding gene is induced by Pi deficiency. The Pi-responsive genes and Pi transporter genes are positively regulated by OsPHL7. The overexpression of OsPHL7 enhanced the tolerance of rice plants to Pi starvation, whereas the RNA interference-based knockdown of this gene resulted in increased sensitivity to Pi deficiency. Transgenic rice plants overexpressing OsPHL7 produced more roots than wild-type plants under both Pi-sufficient and Pi-deficient conditions and accumulated more Pi in the shoots and roots. In addition, the overexpression of OsPHL7 enhanced rice tolerance to salt stress. Together, these results demonstrate that OsPHL7 is involved in the maintenance of Pi homeostasis and enhances tolerance to Pi deficiency and salt stress in rice. Full article

Phosphate (Pi) starvation is a critical factor limiting crop growth, development, and productivity. Rice (Oryza sativa) R2R3-MYB transcription factors function in the transcriptional regulation of plant responses to various abiotic stresses and micronutrient deprivation, but little is known about their roles in Pi starvation signaling and Pi homeostasis. Here, we identified the R2R3-MYB transcription factor gene OsMYB58, which shares high sequence similarity with AtMYB58. OsMYB58 expression was induced more strongly by Pi starvation than by other micronutrient deficiencies. Overexpressing OsMYB58 in Arabidopsis thaliana and rice inhibited plant growth and development under Pi-deficient conditions. In addition, the overexpression of OsMYB58 in plants exposed to Pi deficiency strongly affected root development, including seminal root, lateral root, and root hair formation. Overexpressing OsMYB58 strongly decreased the expression of the rice microRNAs OsmiR399a and OsmiR399j. By contrast, overexpressing OsMYB58 strongly increased the expression of rice PHOSPHATE 2 (OsPHO2), whose expression is repressed by miR399 during Pi starvation signaling. OsMYB58 functions as a transcriptional repressor of the expression of its target genes, as determined by a transcriptional activity assay. These results demonstrate that OsMYB58 negatively regulates OsmiR399-dependent Pi starvation signaling by enhancing OsmiR399s expression. Full article

Salmonella enterica serovar Typhimurium (S. Typhimurium), an important foodborne pathogen, causes diarrheal illness and gastrointestinal diseases. S. Typhimurium survives and replicates in phagocytic and non-phagocytic cells for acute or chronic infections. In these cells, S. Typhimurium resides within Salmonella-containing vacuoles (SCVs), in which the phosphate (Pi) concentration is low. S. Typhimurium senses low Pi and expresses virulence factors to modify host cells. However, the mechanism by which host cells reduce the Pi concentration in SCVs is not clear. In this study, we show that through the TLR4-MyD88-NF-κB signaling pathway, S. Typhimurium upregulates PIT1, which in turn transports Pi from SCVs into the cytosol and results in Pi starvation in SCVs. Immunofluorescence and western blotting analysis reveal that after the internalization of S. Typhimurium, PIT1 is located on SCV membranes. Silencing or overexpressing PIT1 inhibits or promotes Pi starvation, Salmonella pathogenicity island-2 (SPI-2) gene expression, and replication in SCVs. The S. Typhimurium ΔmsbB mutant or silenced TLR4-MyD88-NF-κB pathway suppresses the expression of the SPI-2 genes and promotes the fusion of SCVs with lysosomes. Our results illustrate that S. Typhimurium exploits the host innate immune responses as signals to promote intracellular replication, and they provide new insights for the development of broad-spectrum therapeutics to combat bacterial infections. Full article

Grapevine leaves contain abundant CaO_x crystals located either within the mesophyll in the form of raphides, or in the bundle sheaths as druses. CaO_x crystals function as internal carbon pools providing CO₂ for a baseline level of photosynthesis, named “alarm photosynthesis”, despite closed stomata; thus, preventing the photoinhibition and the oxidative risk due to carbon starvation under adverse conditions. Structural and functional leaf traits of acclimated grapevine plants (Vitis vinifera L. cv. Assyrtiko) were investigated in response to water availability, in order to evaluate the dynamic functionality of CaO_x. Leaf water potential, leaf area, leaf mass per area, stomatal properties, gas exchange parameters and performance index (PI) were decreased in leaves of vines acclimated to water deficit in comparison to the leaves of well-irrigated vines, although the chlorophyll fluorescence parameters showed that the operational efficiency of the photosystem II (PSII) photochemistry (F_v/F_m) did not change, indicating that the photosynthetic apparatus was not subjected to water stress. During the afternoon, more than half of the morning’s existing druses disappeared in the drought-acclimated leaves. Also, the raphides’ area of the drought-acclimated leaves was reduced more than that of the well-watered leaves. The substantial decomposition of druses under water deficit conditions compared to that of the raphides may have important implications for the maintenance of their different though overlapping roles. According to the results, it seems likely that, under water deficit conditions, a mechanism of “alarm photosynthesis” provides an additional tolerance trait in the leaves of Vitis vinifera cv. Assyrtiko; hence, leaf structure relates to function. Full article

Phosphorus (P) is an essential plant macronutrient; however, its availability is often limited in soils. Plants have evolved complex mechanisms for efficient phosphate (Pi) absorption, which are responsive to changes in external and internal Pi concentration, and orchestrated through local and systemic responses. To explore these systemic Pi responses, here we identified AtMYB44 as a phloem-mobile mRNA, an Arabidopsis homolog of Cucumis sativus MYB44, that is responsive to the Pi-starvation stress. qRT-PCR assays revealed that AtMYB44 was up-regulated and expressed in both shoot and root in response to Pi-starvation stress. The atmyb44 mutant displayed higher shoot and root biomass compared to wild-type plants, under Pi-starvation conditions. Interestingly, the expression of PHOSPHATE TRANSPORTER1;2 (PHT1;2) and PHT1;4 was enhanced in atmyb44 in response to a Pi-starvation treatment. A split-root assay showed that AtMYB44 expression was systemically regulated under Pi-starvation conditions, and in atmyb44, systemic controls on PHT1;2 and PHT1;4 expression were moderately disrupted. Heterografting assays confirmed graft transmission of AtMYB44 transcripts, and PHT1;2 and PHT1;4 expression was decreased in heterografted atmyb44 rootstocks. Taken together, our findings support the hypothesis that mobile AtMYB44 mRNA serves as a long-distance Pi response signal, which negatively regulates Pi transport and utilization in Arabidopsis. Full article

Phosphorus (P) is an important nutritional element needed by plants. Roots obtain P as inorganic phosphate (Pi), mostly in H₂PO⁻₄ form. It is vital for plants to have a sufficient supply of Pi since it participates in important processes like photosynthesis, energy transfer, and protein activation, among others. The physicochemical properties and the organic material usually make Pi bioavailability in soil low, causing crops and undomesticated plants to experience variations in accessibility or even a persistent phosphate limitation. In this study, transcriptome data from pepper roots under low-Pi stress was analyzed in order to identify Pi starvation-responsive genes and their relationship with metabolic pathways and functions. Transcriptome data were obtained from pepper roots with Pi deficiency by RNASeq and analyzed with bioinformatic tools. A total of 97 differentially expressed genes (DEGs) were identified; Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment revealed that metabolic pathways, such as porphyrin and chlorophyll metabolism, were down-regulated, and galactose and fatty acid metabolism were up-regulated. The results indicate that bell pepper follows diverse processes related to low Pi tolerance regulation, such as the remobilization of internal Pi, alternative metabolic pathways to generate energy, and regulators of root development. Full article