Induction of <i>Rhizopus oryzae</i> Germination Under Starvation Using Host Metabolites Increases Spore Susceptibility to Heat Stress

Turgeman, Tidhar; Kakongi, Nathan; Schneider, Avishai; Vinokur, Yakov; Teper‐Bamnolker, Paula; Carmeli, Shmuel; Levy, Maggie; Skory, Christopher D.; Lichter, Amnon; Eshel, Dani

doi:10.1094/phyto-08-13-0245-r

Cited by 8 publications

(7 citation statements)

References 28 publications

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“…In a previous work, we isolated a fraction within the sweet potato extract (SPAF) that was found to induce R . delemar spore germination [ 7 ]. The pH of the SPAF was acidic (pH 4.7) and when it was modified, the optimal pH range for R .…”

Section: Resultsmentioning

confidence: 99%

“…Preparation, extraction and purification of sweet potato ( Ipomoea batatas L. cv. Georgia Jet) active fraction (SPAF) were performed according to Turgeman et al [ 7 ]. Fungal spores were treated with SPAF in purified water as the test treatment or purified water as a negative control.…”

Section: Methodsmentioning

confidence: 99%

“…The factors triggering spore germination are diverse; they are based on the adaptations and requirements of the fungal species and they differ among species. Wound-invading fungi such as Rhizopus delemar and Penicillium expansum require nutrients that often originate from host wounds to induce spore germination [ 6 , 7 ]. Fungal spores have been optimally induced for germination in the presence of a mixture of amino acids, as in the case of Rhizopus oligosporus [ 8 ] and Aspergillus flavus [ 9 ].…”

Section: Introductionmentioning

confidence: 99%

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The Role of Aquaporins in pH-Dependent Germination of Rhizopus delemar Spores

et al. 2016

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Rhizopus delemar and associated species attack a wide range of fruit and vegetables after harvest. Host nutrients and acidic pH are required for optimal germination of R. delemar, and we studied how this process is triggered. Glucose induced spore swelling in an acidic environment, expressed by an up to 3-fold increase in spore diameter, whereas spore diameter was smaller in a neutral environment. When suspended in an acidic environment, the spores started to float, indicating a change in their density. Treatment of the spores with HgCl2, an aquaporin blocker, prevented floating and inhibited spore swelling and germ-tube emergence, indicating the importance of water uptake at the early stages of germination. Two putative candidate aquaporin-encoding genes—RdAQP1 and RdAQP2—were identified in the R. delemar genome. Both presented the conserved NPA motif and six-transmembrane domain topology. Expressing RdAQP1 and RdAQP2 in Arabidopsis protoplasts increased the cells' osmotic water permeability coefficient (Pf) compared to controls, indicating their role as water channels. A decrease in R. delemar aquaporin activity with increasing external pH suggested pH regulation of these proteins. Substitution of two histidine (His) residues, positioned on two loops facing the outer side of the cell, with alanine eliminated the pH sensing resulting in similar Pf values under acidic and basic conditions. Since hydration is critical for spore switching from the resting to activate state, we suggest that pH regulation of the aquaporins can regulate the initial phase of R. delemar spore germination, followed by germ-tube elongation and host-tissue infection.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The Role of Aquaporins in pH-Dependent Germination of Rhizopus delemar Spores

et al. 2016

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“…Apoptosis is characterized by a number of intracellular phenomena, including membrane blebbing, chromatin condensation and nuclear DNA fragmentation. Detection of DNA fragmentation is a widely accepted method to assay for apoptosis (26,27). Fragmentation may be visualized by and detected in situ by incorporating labeled nucleotides onto the free 3'OH ends of the fragments using TdT enzyme followed by detection of the labeled molecules.…”

Section: Discussionmentioning

confidence: 99%

“…Cell apoptosis was determined by the terminal deoxynucleotidyl transferase (TdT) mediated dUTP nick end-labeling (TUNEL) assay (26,27) …”

Section: Methodsmentioning

confidence: 99%

Chrysin induces cell apoptosis in human uveal melanoma cells via intrinsic apoptosis

Xue

Chen

et al. 2016

Oncology Letters

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Abstract. Uveal melanoma is the most common intraocular malignant tumor in adults. Chrysin is a flavonoid present in honey, propolis, various plants and herbs. In the present study, the cytotoxic effects of chrysin were investigated on human uveal melanoma cell lines (M17 and SP6.5) and associated signaling pathways, and a comparison to the effects on normal ocular cells [scleral fibroblasts and retinal pigment epithelial (RPE) cells] was performed. The effects of chrysin on cell viability were assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Cell apoptosis was determined by using terminal deoxynucleotidyl transferase mediated dUTP nick end-labeling assay. Mitochondrial permeability was determined by JC-1 fluorescein analysis. Cytosol cytochrome c levels, and the activities of caspase-3, -8 and -9 were measured by enzyme-linked immunosorbent assay or colorimetric assay. Chrysin reduced the viability of cultured human melanoma cells in a dose-dependent manner (0, 10, 30 and 100 µM) with IC 50 at 28.3 and 35.8 µM in SP6.5 and M17 cell lines, respectively. Chrysin at 30-100 µM levels selectively reduced the viability of melanoma cells without affecting the viability of scleral fibroblasts and RPE cells. Chrysin increased mitochondrial permeability, the levels of cytosol cytochrome c, and caspase-9 and -3 activities, but not capase-8 activity in uveal melanoma cells. The results of the present study indicate that chrysin induces apoptosis of human uveal melanoma cells via the mitochondrial signaling pathway and suggest that chrysin may be a promising agent in the treatment of uveal melanoma.

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