Project description:Date palm (Phoenix dactylifera L.), is a widely cultivated crop across North Africa, with about 300 thousand tons of fruits produced per year, in Tunisia. A wide range of fungal pathogens has been associated with leaf spots of date palm, Alternaria species being the most frequently reported. Symptomatic leaves of Deglet Nour variety were randomly collected in six localities in Tunisia. We used a polyphasic approach to identify 45 Alternaria and five Curvularia strains isolated from date palm, confirming their pathogenicity. Sequencing of allergen Alt-a1, glyceraldehyde-3-phosphate dehydrogenase (gpd) and calmodulin genes allowed us to group 35 strains in Alternaria Section, and 10 strains in Ulocladioides section. Based on sequencing analyses of Internal Transcribed Spacer, gpd and elongation factor genomic regions, all Curvularia strains were identified as Curvularia spicifera. All Alternaria and Curvularia species tested on date palm plantlets proved to be pathogenic, fulfilling Koch's postulates. Although no significant differences were observed among the species, the highest mean disease severity index was observed in A. arborescens, while the lowest corresponded to C. spicifera. The capability of these strains to produce mycotoxins in vitro was evaluated. None of the A. consortialis strains produced any known Alternaria mycotoxin, whereas more than 80% of the strains included in Alternaria section Alternaria produced variable amounts of multiple mycotoxins such as alternariol, alternariol monomethyl ether, altenuene, tenuazonic acid and tentoxin. Curvularia spicifera strains produced detectable traces of fumonisins B. This work reports a first comprehensive multidisciplinary study of mycotoxigenic Alternaria species and C. spicifera associated with leaf spot disease on date palm.
Project description:Climate change is increasing the frequency and intensity of warming and drought periods around the globe, currently representing a threat to many plant species. Understanding the resistance and resilience of plants to climate change is, therefore, urgently needed. As date palm (Phoenix dactylifera) evolved adaptation mechanisms to a xeric environment and is able to tolerate large diurnal and seasonal temperature fluctuations, we studied the protein expression changes in their leaves, volatile organic compound emissions, and photosynthesis in response to variable growth temperatures and soil water deprivation. Plants were grown under controlled environmental conditions under simulated Saudi Arabian summer and winter climates followed by drought stress. We show that date palm is able to counteract the harsh conditions of the Arabian Peninsula by adjusting the abundances of proteins related to the photosynthetic machinery, abiotic stress and secondary metabolism. Under summer climate and water deprivation, these adjustments included efficient protein expression response mediated by heat shock proteins and the antioxidant system to counteract reactive oxygen species formation. Proteins related to secondary metabolism were downregulated, except for the P. dactylifera isoprene synthase (PdIspS), which was strongly upregulated in response to summer climate and drought. This study reports for the first time, the identification and functional characterization of the gene encoding for PdIspS, allowing future analysis of isoprene functions in date palm under extreme environments. Overall, the current results show that protein reprogramming of date palm leaves contribute to heat and drought tolerance. We conclude that the protein plasticity of date palm is one important mechanism of molecular adaptation to remarkable environmental fluctuations.
Project description:Purpose: To identify conserved and novel miRNAs in date palm and, most importantly, to identify miRNAs that could play a role in salt tolerance Methods: we generated sRNA libraries from the leaves and roots of NaCl-treated and untreated seedlings of date palm,then Deep sequencing of these four sRNA libraries,last The bioinformatics analysis,further validated using semi-quantitative PCR (qPCR). Results: Deep sequencing of these four sRNA libraries yielded approximately 251 million reads. The bioinformatics analysis has identified 153 homologs of conserved miRNAs, 89 miRNA variants, and 180 putative novel miRNAs in date palm. Expression profiles under salinity revealed differential regulation of most miRNAs in date palm. In leaves, all of the identified miRNAs were affected by the salinity treatment, and the majority (75%) of them were upregulated, whereas in roots, only 33% of the miRNAs were upregulated, but 44% of them were downregulated, while the remaining miRNAs (22%) were unaffected by the treatment. The salt responsiveness of some of these miRNAs was further validated using semi-quantitative PCR (qPCR). Some of the predicted targets for the identified miRNA include genes with known functions in plant salt tolerance, such as potassium channel AKT2-like proteins, vacuolar protein sorting-associated protein, and calcium-dependent and mitogen-activated proteins. As one of the first cultivated trees in the world with a wide range of abiotic stress tolerance, date palm contains a large population of conserved and nonconserved miRNAs that function at the posttranscriptional level. Conclusions: This study provided insights into miRNA-mediated gene expression that are important for adaptation to salinity in date palms.
Project description:Date palm (Phoenix dactylifera) cultivar Khalas was drought treated and two tissues (root and shoot) were compared to control conditions by RNAseq.
Project description:Two tissues (root and shoot) of a salt tolerant (Khalas) and a salt sensitive (Nabut Saif) variety of date palm (Phoenix dactylifera) were salt treated and compared to control conditions by RNAseq.
Project description:Date palms are extremely stress tolerant. The aim of the experiment was to evaluate, how date palm leaves react to application of the drought stress hormone ABA on the transcriptional level, and to compare the resulting data with those obtained from the stress sensitive Arabidopsis thaliana. The experiment thus should help us to understand how date palms manage their stress tolerance in comparison to sensitive plants. Single cut pinneates from date palm leaves were treated for 2 h with CO2-free air in darkness, then illuminated for 4 h at a photon flux rate of 620 mol m2 s-1. Following this pre-incubation, 25 M ABA was fed via the petiole. After 2 h, RNA was extracted from the pinneates. Controls were treated equally with ABA-free solution.
Project description:In 2017-2018, extensive symptoms of sudden decline and fruit rot were observed on date palms in southern Tunisia. Samples of diseased plants were randomly collected in six localities. Based on morphological identification, Fusarium was the most frequent fungal genus detected. A sequencing of translation elongation factor, calmodulin, and second largest subunit of RNA polymerase II genes was used to identify 63 representative Fusarium strains at species level and investigate their phylogenetic relationships. The main species detected was Fusariumproliferatum, and at a much lesser extent, Fusariumbrachygibbosum, Fusariumcaatingaense, Fusariumclavum, Fusariumincarnatum, and Fusariumsolani. Pathogenicity on the DegletNour variety plantlets and the capability to produce mycotoxins were also assessed. All Fusarium species were pathogenic complying Koch's postulates. Fusariumproliferatum strains produced mainly fumonisins (FBs), beauvericin (BEA), and, to a lesser extent, enniatins (ENNs) and moniliformin (MON). All F.brachygibbosum strains produced low levels of BEA, diacetoxyscirpenol, and neosolaniol; two strains produced also T-2 toxin, and a single strain produced HT-2 toxin. Fusariumcaatingaense, F.clavum, F.incarnatum produced only BEA. Fusariumsolani strains produced MON, BEA, and ENNs. This work reports for the first time a comprehensive multidisciplinary study of Fusarium species on date palms, concerning both phytopathological and food safety issues.