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Expression analysis was carried out to characterise the level and time of expression of two senescence related cDNAs, LSC650 and LSC54, in Brassica napus and Arabidopsis thaliana. The extent of DNA sequence similarity showed that the LSC650 gene may en-code the catalase homologous to Cat3 in Arabidopsis thaliana the role of which is to scav-enge H2O2. Also, LSC54 gene encodes a metallothionein protein that may detoxify metal ions in plant cells. Plant leaves were characterised at different developmental stages by biochemical analysis, including chlorophyll and protein assays. Northern analysis re-vealed strong levels of LSC650 and LSC54 expression in senescent leaves and lower levels in mature green leaves, but very weak or no expression in young leaves in B. napus. The transcription of genes, LSC650 and LSC54, was almost at the same level with few changes between maturity and senescence in leaves of Arabidopsis at different plant growth phases, being due to a possible unknown stress. The results indicate that both genes stud-ied may act as antioxidants, and have a role in scavenging active oxygen species (AOS) caused by catabolism of macromolecules during senescence.

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Many plants of tropical and subtropical areas are severely damaged when exposed to chilling temperatures between 2 and 15°C. Arabidopsis thaliana is chilling tolerant and, therefore provides an alternative model plant system for the identification of chilling tolerance traits. To determine whether the expression of Cu/Zn-superoxide dismutase 2 (CSD2) would increase superoxide-scavenging capacity and thereby improve the survival rate of chilling sensitive (chs) mutants of Arabidopsis, four chs mutant (chs1-1, chs1-2, chs2-1 and chs2-2) and wild-type plants were grown under low (chilling at 13 °C and 4 °C) and normal growth (23 °C) temperatures. The expression of CSD2 was not detected during cold stress treatments, while the wild plants showed the expression of CSD2 under cold stress. The increase of antioxidant enzymes activities (POX and SOD) showed the role of these enzymes in the protection of the chs mutants under chilling treatment, also the increase in polyphenol oxidase activity shows the role of that in the emergence of chlorosis phenotype. The lack of expression of CSD2 gene in chs mutants grown at chilling temperature would support the hypothesis that the expression of these genes was affected due to mutation in CHS genes, when they are chilled.

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Botrytis cinerea is one of the most important harmful fungi affecting agricultural products. This study focused on the expression changes of Arabidopsis thaliana infected with this fungus. The expression dataset of a microarray and two RNA-sequencing were integrated using the respective software. The list of differentially expressed genes was extracted, and the key genes with altered expression were identified through Cytoscape software. These key genes co-expression patterns and functional enrichment were analyzed. Subsequently, microRNAs and transcription factors associated with these genes were predicted. Ten genes, including GAPA-2, SBPASE, CRB, HCEF1, CaS, ATPD, LIL3:1, PSAH2, PRK, and PMDH2, were identified as crucial down-regulated genes. Additionally, ten genes, namely WRKY33, CZF1, SZF1, STZ, ERF11, RHL41, BAP1, AT1G07135, CMPG2, and TET8, were highlighted as key up-regulated genes. The key roles of the hub genes with a decreased expression included processes and pathways associated with the reductive pentose phosphate cycle, photosynthesis, cold response, fructose and sucrose metabolism, defense response against bacteria, and gluconeogenesis. The key over-expressed genes played important roles in responding to chitin, oxygen deprivation, temperature fluctuations, injuries, fungal attacks, and gene transcription functions. Key genes were associated with ath-miR850, ath-miR393a-5p, and ath-miR393b-5p. Transcription factor SPL7 was linked to the transcription of down-regulated key genes, while transcription factors SARD1, PIF5, CAMTA1, HY5, WRKY33, TOC1, CAMTA3, CAMTA2, BZR1, FAR1, and CAMTA5 were also predicted to be associated with up-regulated genes. Some of these results have not previously been reported. Therefore, they could be used to design practical experiments exploring the interaction between plants and pathogenic fungi.
 

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In this study, we examined the efficacy of the artificial microRNAs (amiRNAs) technology in targeting the HOS1 gene for the enhancement of cold stress tolerance in Arabidopsis thaliana Ler-0 ecotype. The impact of athHOS1-amiRNA overexpression on the response of transgenic plants to cold stress was assessed using RT-qPCR in 3-week-old seedlings of the T3 generation. Additionally, the response of wild-type plants of the same age to cold stress (4ºC) for various durations (6, 12, 24, 48, and 96 hours) was also evaluated. Comparative analysis revealed that athHOS1-amiRNA downregulated athHOS1 in transgenic plants after prolonged exposure to low temperature (48 h and 96 h) (Pearson’s correlation coefficient of -0.407; P<0.05). Interestingly, while prolonged cold stress at 96 h led to a significant upregulation of athHOS1 in wild-type plants, the suppression of athHOS1-amiRNA in transgenic plants disrupted the expected circadian rhythm of athHOS1 by preventing its upregulation. Furthermore, T3 plants that had been cold-acclimated exhibited a 17% increase in freezing tolerance (-1 to -8°C) compared to wild-type plants, indicating the success of this approach in enhancing Arabidopsis tolerance to low temperatures, at least in the Ler-0 ecotype. In order to gain a deeper understanding of the intricate dynamics of gene/protein networking during cold acclimation and its interaction with the athHOS1-amiRNA approach, further characterization is required. This includes measuring the expression levels and half-life of athHOS1-amiRNA and HOS1 mRNA, as well as evaluating the protein level of HOS1 and its direct targets, such as ICE1, in different Arabidopsis ecotypes and at different time intervals of low temperature exposure.