Complete genome sequencing of Piper yellow mottle virus infecting black pepper, betelvine, and Indian long pepper.

The complete genome of the Piper yellow mottle virus (PYMoV), a Badnavirus belonging to the family Caulimoviridae, was sequenced from three naturally infected hosts namely, black pepper, betelvine, and Indian long pepper. The genome length of the three virus strains (one from each of the three host species) varied from 7,559 to 7,584 nucleotides, and all the three strains possessed four open reading frames (ORFs) I to IV that potentially encode proteins of 15.67, 17.08, 218.6, and 17.22 kDa, respectively. ORF III encodes a polyprotein consisting of viral movement protein, trimeric dUTPase, zinc finger, aspartic protease, reverse transcriptase, and RNase H whereas ORF I, II, and IV encode proteins of unknown functions. The complete genome sequences at the nucleotide level were 89-99 % identical with one available sequence of PYMoV and 39-56 % identical with other badnaviruses, indicating that all three are strains of PYMoV. Nucleotide and amino acid sequences of ORF I-IV and of the intergenic region (IR) were 80-100 % identical among PYMoV strains. Phylogenetic analysis of ORF III amino acid sequences showed the PYMoV strains forming a distinct cluster well separated from other badnaviruses. Among other badnaviruses, Fig badnavirus 1 (FBV-1) was the one most closely related to PYMoV.

Down-regulation of osmotin (PR5) gene by virus-induced gene silencing (VIGS) leads to susceptibility of resistant Piper colubrinum Link. to the oomycete pathogen Phytophthora capsici Leonian.

Piper colubrinum Link., a distant relative of Piper nigrum L., is immune to the oomycete pathogen Phytophthora capsici Leonian that causes 'quick wilt' in cultivated black pepper (P. nigrum). The osmotin, PR5 gene homologue, earlier identified from P. colubrinum, showed significant overexpression in response to pathogen and defense signalling molecules. The present study focuses on the functional validation of P. colubrinum osmotin (PcOSM) by virus induced gene silencing (VIGS) using Tobacco Rattle Virus (TRV)-based vector. P. colubrinum plants maintained under controlled growth conditions in a growth chamber were infiltrated with Agrobacterium carrying TRV empty vector (control) and TRV vector carrying PcOSM. Three weeks post infiltration, viral movement was confirmed in newly emerged leaves of infiltrated plants by RT-PCR using TRV RNA1 and TRV RNA2 primers. Semi-quantitative RT-PCR confirmed significant down-regulation of PcOSM gene in TRV-PcOSM infiltrated plant compared with the control plants. The control and silenced plants were challenged with Phytophthora capsici which demonstrated that knock-down of PcOSM in P. colubrinum leads to increased fungal mycelial growth in silenced plants compared to control plants, which was accompanied by decreased accumulation of H2O2 as indicated by 3,3'-diaminobenzidine (DAB) staining. Thus, in this study, we demonstrated that Piper colubrinum osmotin gene is required for resisting P. capsici infection and has possible role in hypersensitive cell death response and oxidative burst signaling during infection.

Histochemical visualization of ROS and antioxidant response to viral infections of vegetable crops grown in Azerbaijan.

Extremes of environmental conditions, such as biotic stresses, strongly affect plant growth and development and may adversely affect photosynthetic process. Virus infection is especially problematic in crops, because unlike other diseases, its impact cannot be reduced by phytosanitary treatments. The vegetable crops (Solanum lycopеrsicum L, Cucurbita melo L., Cucumis sativus L., Piper longum L., Solánum melongéna L., Vicia faba L.) showing virus-like symptoms were collected from fields located in the main crop production provinces of Azerbaijan. Infection of the plants were confirmed by Enzyme-linked immunosorbent assay using commercial kits for the following viruses: Tomato yellow leaf curl virus, Tomato mosaic virus, Tomato chlorosis virus, Melon necrotic spot virus and Cucumber mosaic virus, Bean common mosaic virus and Bean yellow mosaic virus. Generation sites of superoxide and hydrogen peroxide radicals and activities of enzymes involved in the detoxification of reactive oxygen species (catalase, glutathione reductase, ascorbate peroxidase, guaiacol peroxidase and superoxide dismutase) were examined in uninfected leaves and in leaves infected with viruses. High accumulation of superoxide and hydrogen peroxide radicals was visualized in infected leaves as a purple discoloration of nitro blue tetrazolium and 3,3'-diaminobenzidine tetrahydrochloride. It was found that the activities of APX and CAT significantly increased in all infected samples compared with non-infected ones. Dynamics of GR and Cu/Zn-SOD activities differed from those of CAT and APX, and slightly increased in stressed samples. Electrophoretic mobility profiling of APX, GPX and CAT isoenzymes was also studied.