Search

The thermophilic fungus Gymnascella thermotolerans GTE-21 produces a significant amount of both volatile and nonvolatile compounds with potent antifungal and anticancer properties. Gas chromatography-mass spectrometry (GC-MS) was utilized to identify 14 volatile organic compounds (VOCs) released by G. thermotolerans. The most predominant compound identified was diisooctyl phthalate, constituting 71.99% of the total VOCs, followed by phenol, 2-methoxy-4-(2-propenyl) at 7.12%. The GTE-21's VOCs demonstrated significant antifungal growth inhibition activity of 42.5% against Fusarium solani and 39.03% against Alternaria alternata. Additionally, GTE-21's crude extract exhibited substantial antibacterial effects, evidenced by inhibition zones of 1.5 cm against S. epidermidis, 1.4 cm against C. ciferrii, and 1.3 cm against S. aureus. The CHR2RClR2R:MeOH (1:1) fraction was more effective against human pathogens, producing the largest zones of inhibition of 1.1 and 1.03 cm against S. epidermidis and C. ciferrii, respectively. The evaluation of GTE-21's antifungal activity using the Evans blue assay showed that fungal spores treated with GTE-21's crude extract exhibited 96.2% inhibition at a concentration of 25 mg/ml. Similarly, the fractions CH2Cl2:MeOH (1:1) and CH2Cl2:MeOH (9:1) demonstrated spore inhibition rates of 96.3% and 94.3%, respectively. The EtOAc crude extract demonstrated pronounced cytotoxic effects against the SKOV-3 and MDA-MB-231 cancer cell lines. For SKOV-3, cell viability decreased to 3.40% and 0.47% at concentrations of 50 and 100 μL, respectively. In the case of MDA-MB-231, cell viability was reduced to 0.19% at both 50 and 100 μL concentrations. [ABSTRACT FROM AUTHOR]

Rot disease is responsible for serious economic losses related to okra (Abelmoschus esculentus) crops cultivated in Upper Egypt. Colonies with a consistent morphology were isolated from the infected okra stems and leaves and subjected to morphological and molecular examinations. The causal pathogen was identified as Cochliobolus spicifer based on morphological fungus descriptions, as well as on the amplified 28S rDNA and internal transcribed spacer region (ITS) sequences, which showed 99%–100% similarity to the sequences of C. spicifer - CSN-20 strains. The volatile and non-volatile organic compounds (VOCs and n-VOCs, respectively) produced by the endophytic fungi that are associated with the medicinal plant Solenostemma arghel , namely Fusarium solani -F4-1007, Penicillium verrucosum -F2-1006, and Aspergillus terreus -F5-1008, inhibited the growth of the C. spicifer pathogen by 34.2%,31.4%, and 30.5%, respectively. In total,27 VOCs were identified by GC/MS, among which eight were specific to A. terreus -F5-1008, eight to P. verrucosum -F2-1006, and three to F. solani -F4-1007, whereas nine VOCs were commonly produced by the three endophytic fungi. Moreover, F. solani -F4-1007-produced VOCs and n-VOCs exhibited the highest antifungal activity, with 37.27% and 37.1% inhibition against C. spicifer colony growth, respectively. The potent antifungal VOCs produced by F. solani -F4-1007 were identified as 3,4-dihydro-2 h-1,5-(3″-t-butyl) benzodioxepine, 4-(2-hydroxyethyl) phenol, and phenylethyl alcohol using GC/MS. Therefore, F. solani -F4-1007 was tested as a potential biocontrol agent against C. spicifer- CSN-20 using an in-planta assay. Okra plants treated with endophytic F. solani -F4-1007did not show any disease symptoms, whereas those that were not treated with F. solani -F4-1007 exhibited severe disease symptoms when challenged with inoculation of the C. spicifer pathogen. Our results demonstrated the contribution of the endophytic fungus F. solani -F4-1007 as a potential biocontrol agent against the C. spicifer pathogen, to improve okra growth. [ABSTRACT FROM AUTHOR]

The fruit rot disease of sweet melon is responsible for serious of economic crop losses that have occurred sporadically in Aswan, Egypt recently. The symptoms appeared as water-soaking lesion which advanced to the rotting of the fruit surface. White mycelial mats with brown color inside appear on the lesion at the surface of the fruit. Disease symptoms, morphological and mycological characteristics, pathogenicity and molecular identification, indicated as Fusarium solani, are the disease causative. When healthy fruits of sweet melon sprayed with spore suspension of the isolated F. solani, the disease symptoms appeared as white spot, which enlarged and turned brown. Dual culture techniques showed that the endophytic fungi, Aspergillus terreus, Fusarium solani and Penicillium verrucosum isolated from the medicinal plant Solenostemma arghel inhibited the pathogen growth in variable levels. The extract of ethyl acetate of the endophytic fungal was found to be active against Fusarium solani. The ethyl acetate fractions of Penicillium verrucosum inhibited the pathogen growth by 47% while A. terreus, and F. solani showed inhibition percentage of 45% and 40%, respectively [ABSTRACT FROM AUTHOR]

Tomato (Solanum lycopersicum L.) is an important worldwide vegetable crop. This paramount crop would be infected by a serious set of pathogenic fungal diseases. Growth and production are hampered by early blight caused by Alternaria phragmospora. In vitro the production of growth promoted hormone indole acetic acid (IAA) by Aspergillus flavus isolated from the medicinal plant, Euphorbia geniculata was stimulated in culture media supplemented or not by tryptophan (120 and 40 μg mL−1) respectively. The blue fluorescence test showed that the endophytic A. flavus was lacking to produce aflatoxins. Inoculation of S. lycopersicum with A. flavus enhanced the fresh weight (FW) and plant length (PL) of S. lycopersicum significantly in comparison to untreated plants. The PL of treated plants was 39.05 cm ± 3.16, while control was 22.19 cm ± 4.54. IAA stimulated overproduction of lateral roots and root hairs in treated plants compared to control. After spraying with A. phragmospora , the treated plant with A. flavus showed healthy leaves and completely protected (100%) from the disease symptoms. There were significant increases in chlorophyll (1.68 mg g−1 FW), flavonoids (105.4 mg g−1 dry weight), carbohydrates (155.5 mg g−1 dry weight), phenolics (0.9 mg g−1 dry weight) and total proteins contents (94.13 mg g−1 dry weight) in treated plants relative to untreated control plants. Our findings demonstrated the contribution of A. flavus to improve the growth and the secondary metabolites contents of tomato, which subsequently leads to the improvement of the resistance of this plant to an aggressive plant pathogen like A. phragmospora. [ABSTRACT FROM AUTHOR]

In plants as well as in animals, hundreds to thousands of 45S rRNA gene copies localize in Nucleolus Organizer Regions (NORs), and the activation or repression of specific sets of rDNA depends on epigenetic mechanisms. Previously, we reported that the Arabidopsis thaliana nucleolin protein NUC1, an abundant and evolutionarily conserved nucleolar protein in eukaryotic organisms, is required for maintaining DNA methylation levels and for controlling the expression of specific rDNA variants in Arabidopsis. Interestingly, in contrast with animal or yeast cells, plants contain a second nucleolin gene. Here, we report that Arabidopsis NUC1 and NUC2 nucleolin genes are both required for plant growth and survival and that NUC2 disruption represses flowering. However, these genes seem to be functionally antagonistic. In contrast with NUC1 , disruption of NUC2 induces CG hypermethylation of rDNA and NOR association with the nucleolus. Moreover, NUC2 loss of function triggers major changes in rDNA spatial organization, expression, and transgenerational stability. Our analyses indicate that silencing of specific rRNA genes is mostly determined by the active or repressed state of the NORs and that nucleolin proteins play a key role in the developmental control of this process. [ABSTRACT FROM AUTHOR]

While plant rRNA gene organization and expression have been studied for several decades, the repetitive nature and high sequence identity between the tandemly-repeated units has prevented precise studies to determine which units are active and elucidate mechanisms of spatial and temporal transcriptional control. We have detected four variants among rRNA genes of Arabidopsis thaliana by analysis of the 3' external spacer region. Surprisingly, the most abundant variant, representing ~50% of the genes, is not expressed in wild-type plants but is transcribed in lines mutated in one of the two nucleolin genes. Analysis of Arabidopsis ecotypes indicated considerable variability in numbers and presence/absence of variants, although more closely-related ecotypes show similar profiles. Sequence analysis showed that one of the variants is not only unexpectedly located within a 5S RNA gene cluster in the pericentromeric region of chromosome 3 but is also potentially highly expressed in wild-type plants. We present a model to explain how transcription of this this unusual variant, maintained in an active state by nucleolin binding, could be involved in control of expression of the major variant, while absence of nucleolin leads to silencing of the minor variant and consequent expression of the major variant.

In eukaryotes, 45S rRNA genes are arranged in tandem arrays in copy numbers ranging from several hundred to several thousand in plants. Although it is clear that not all copies are transcribed under normal growth conditions, the molecular basis controlling the expression of specific sets of rRNA genes remains unclear. Here, we report four major rRNA gene variants in Arabidopsis thaliana. Interestingly, while transcription of one of these rRNA variants is induced, the others are either repressed or remain unaltered in A. thaliana plants with a disrupted nucleolin-like protein gene (Atnuc-L1). Remarkably, the most highly represented rRNA gene variant, which is inactive in WT plants, is reactivated in Atnuc-L1 mutants. We show that accumulated pre-rRNAs originate from RNA Pol I transcription and are processed accurately. Moreover, we show that disruption of the AtNUC-L1 gene induces loss of symmetrical DNA methylation without affecting histone epigenetic marks at rRNA genes. Collectively, these data reveal a novel mechanism for rRNA gene transcriptional regulation in which the nucleolin protein plays a major role in controlling active and repressed rRNA gene variants in Arabidopsis., Competing Interests: The authors have declared that no competing interests exist.