فهرست مطالب a. afsharifar

Canna indica (canna) a species in the Cannaceae family, is a perennial ornamental plant widely used in landscape designing. Different species of plant viruses have been reported which infect this plant and act as a significant threat to canna plants, leading to a range of symptoms and a decrease in their decorative values, as well as lower quality propagated materials and significant financial losses. Canna cultivars that are extensively cultivated for their ornamental values are susceptible to a recently discovered Potyvirus known as canna yellow streak virus (CaYSV). This virus has infected many canna cultivars found in gardens, leading to significant impact and concern in horticultural settings. During a survey conducted in the summer of 2022, severe veinal chlorosis and veinal streaking symptoms were observed on the leaves of canna plants in the green space of Yazd City, Iran. Total genomic RNA was extracted from symptomatic leaves of 20 canna samples and one symptomless sample (negative control), and subjected to RT-PCR using a potyvirus degenerate primer pair (NIb3R, NIb2F). RT-PCR resulted in the amplification of a DNA fragment with the expected size of approximately 350 bp in all of the symptomatic samples, whereas no DNA fragment was obtained from a symptomless plant. The amplified DNA fragment was subjected to the Sanger sequencing method, and its size was confirmed to be exactly 350 bp. Sequence analysis of the nucleotide sequence of this amplicon with the same region of other corresponding CaYSV isolates in the GenBank revealed that the Iranian CaYSV isolate was the most similar (99.05%) to an isolate from Russia (Acc. No.  MG_545919.1) and the less similar (89.59%) to a CaYSV isolate from United Kingdom (Acc. No.  EF_466139.1).

Research on natural compounds provides new alternatives for effective and sustainable control of plant viral pathogens. Herein, we prepared and investigated the in vitro antiviral activity of 60 plant species from 22 families. The hydroethanolic extracts of Rhus coriaria, Chenopodium quinoa and Ailanthus altissima have strong inhibitions on Tobacco Mosaic Virus (TMV) infection. Hydroethanolic extract of C. quinoa with half-maximal Effective Concentration (EC50) value of 1.64 mg mL-1 exhibited the highest inhibitory effect against TMV. The extracts of R. coriaria and A. altissima with EC50 values of 2.82 and 4.42 mg mL-1, being compared with C. quinoa, showed an anti-TMV activity at higher concentrations, respectively. The systemic assay indicated that all of the three extracts reduced the symptoms and negative effects of TMV on tobacco plants. The chemical analysis of C. quinoa extract demonstrated a rich profile of saponins and anthocyanins, while A. altissima and R. coriaria extracts were rich in phenolic compounds. These results displayed that C. quinoa, R. coriaria, and A. altissima extracts had significant antiviral activity, and could be used as suitable sources for discovering new antiviral agents.

Autophagy is a degradation process in eukaryotes through which damaged or unwanted intracellular components are degraded. This process is also involved in plant disease resistance, although its mechanisms are not precisely known. Autophagy is regulated by multiple autophagy-related proteins (ATGs).In this study, we investigated the possible impact of two Barley yellow striate mosaic virus (BYSMV) proteins, i.e., phosphoprotein (P) and ancillary protein 3 (P3), on four important genes involved in autophagy (ATG2, ATG6, ATG7, and AGO1) in N. benthamiana. P and P3 genes were cloned in pCAMBIA-1302 vector under the control of the 2 × 35S promoter and Hemagglutinin tag. Constructs of each gene were agroinfiltrated in the abaxial side of the N. benthamiana leaves. Five days after agroinfiltration, the expression level of these genes was measured using RT- qPCR. The results showed that expression of ATG2, ATG6 and ATG7 genes increased in all treatments (P, P3, P+P3).The level of ATG2 expression was 5.57, 15.6 and 5.6 fold, in P/GFP, P3/GFP and P/P3/GFP treatments, respectively, while a 1.5-fold reduction was obtained in expression of AGO1 in all treatments. These results implied that P and P3 proteins of BYSMV can modify the expression of autophagy related genes in N. benthamiana plant. These findings suggest the involvement of AGO1, ATG6, ATG7 and ATG2 in immune responses of N. benthamiana against BYSMV, which provide a better understanding of plant host defense mechanisms against virus infections and might be an opportunity to exploit a novel antivirus approach.

Barley yellow striate mosaic virus (BYSMV) belongs to the genus Cytorhabdovirusin the family Rhabdoviridae. It causes mosaic and chlorotic striation in gramineous plants and is transmitted by Laodelphax striatellus in a propagative manner. In the present study, nucleotide sequences ofglycoprotein and phosphoprotein genes of BYSMV Zanjan isolate are reported. Following thepurification of viral nucleocapsid, the nucleotide sequence of G and P genes was determined using random-PCR method (rPCR) followed by PCR with specific primers. Putative amino acid sequences of the two proteins were aligned with other members of Rhabdoviridae using CLUSTAL W software and the phylogenetic trees were depicted. BYSMV G and P proteins showed the highest similarity to the Northern cereal mosaic virus (NCMV). In phylogenetic analysis, the viruses were grouped into two main clusters reflecting the Cytorhabdovirus and Nucleorhabdovirus genera. These results support our previous phylogenetic analysis based on polymerase gene.Analysis of transmission efficiency showed that Zanjan, Naghadeh and Sero isolates were transmitted with a higher efficiency than Mashhad isolate by the same biotype of L. striatellus.

Many plant and animal viruses overcome their host defense by encoding protein that suppress post-transcriptional gene silencing (PTGS). Protein 2b in cucumber mosaic virus (CMV) is regarded as a strong suppressor of PTGS. In the present study the 2b gene of CMV was used to transform of tobacco plant. Possibility of induction of resistance to CMV in the tobacco plants was investigated.Two different constructs, S1 and S2, were used to study PTGS of CMV.The designated S2 construct contained a sequence of sense and antisense of coding region of 2b gene, expected a hairpin-like structure transcribed. Control construct (S1) consisted of the same construct without any sequence of 2b gene. These constructs were first made in pHANNIBALL and then ligated into pART27, a plant specific vector. Agrobacterium tumefaciens strain GV3101 was used for stable transformation of Nicotiana tabaccum Var xanthi. Forty regenerated plants were transferred to soil and challenged by CMV inoculation. Thirty three percent of plants showed resistance to CMV while 30% showed delayed in symptom development. Resistance of plants to CMV was confirmed by ELISA. The present study demonstrated that 2b- derived PTGS is an effective plant defense mechanism against CMV and can be used in breeding programs.