Vein Clearing Research Articles

MicroRNA response in potato virus Y infected tobacco shows strain-specificity depending on host and symptom severity

The present study demonstrates how different potato virus Y (PVY) strains affect the miRNA balance in tobacco cv. Samsun. The two prevalent strains PVYNTN and PVYN−Wi caused severe and mild veinal necrosis (VN) respectively, and the unique PVYZ-NTN strain induced milder vein clearing (VCl) in the upper non-inoculated leaves. A single amino acid polymorphisms (SAPs) I252V and a Q412 to R412 substitution in the HC-Pro cistron of the PVYZ-NTN strain might relate to the loss of VN in tobacco. The abundance of 18 out of the 26 tested miRNAs was increased upon infection by the severe strains PVYNTN and PVYN−Wi. Expression of a group of defense related transcripts were increased accordingly. Two miRNAs, nta-miR6020a-5p and nta-miR6164a/b, which target the TIR-NBS-LRR type resistant TMV N genes involving in signal transduction, might correlate with the PVYNTN and PVYN-Wi induced VN. The down-regulated mRNAs, e.g., RAP2-7 and TOE3, PXC3, LRR-RLK, ATHB-14 and TCP4 targeted by nta-miR172, nta-miR390, nta-miR482, nta-miR166 and nta-miR319/159 respectively, were related to regulation of transcription, protein phosphorylation and cell differentiation. The observed strain-specific alteration of miRNAs and their targets are host dependent and corresponds to the symptom severity and the viral HC-Pro RNA levels.

FIRST REPORT OF EGGPLANT MOTTLED DWARF VIRUS IN TOBACCO CROPS IN ALBANIA

In summer 2008 and 2009, tobacco plants of cvs Lovina and Katerini (Samsun) displaying severe stunting, leaf crinkling and vein clearing (VC) (incidence of diseased plants 0.1%) were ob- served in areas of Koritsa and Elbasan (Albania). Leaf extract from five affected plants collected in 2009 was used for mechani- cal inoculations of Nicotiana benthamiana, N. rustica and Gom- phrena globosa. Twenty-thirty days post inoculation, N. benthami- ana developed a systemic VC, while N. rustica reacted with yel- low spots in the inoculated leaves followed by systemic VC. In G. globosa only red local lesions were observed. Leaves from 10 symptomatic and 10 symptomless tobacco plants were collected from different fields and tested serologically by DAS-ELISA us- ing polyclonal antisera to Eggplant mottled dwarf virus (EMDV) (As 0136 antiserum, DSMZ, Braunschweig, Germany). All sam- ples from symptomatic plants tested positive. To confirm the presence of EMDV a one-step RT-PCR as described by Katis et al. (2011) was carried out to the same samples and one of the PCR products was sequenced. BLAST analysis of the obtained sequence revealed 98% nucleotide similarity with the homolo- gous published sequences of the EMDV isolates from tobacco (AM922318), cucumber (AM922317), Pittosporum tobira (AM922320) and 88% with those of virus isolates from eggplant (AM922319) and caper (AM922321), respectively. The obtained sequence was deposited in EMBL-EBI under the accession No. HE601787. EMDV is known since 1969 and is generally consid- ered to be of minor importance. It has been reported to infect to- bacco in Italy and Greece (Chatzivassiliou et al., 2004). To our knowledge this is the first report of EMDV in tobacco in Alba- nia, even though its economic importance is limited.

Recombinants of PVY Strains Predominate Among Isolates from Potato Crop in Poland

Recombinants of PVY Strains Predominate Among Isolates from Potato Crop in Poland 282 Potato virus Y (PVY) isolates collected from potato crops in northern and central Poland from 1995 to 2009 were characterized by serological and biological assays. From these, 112 isolates collected from 2006 to 2009 were additionally analyzed by one-step triplex Reverse Transcription-Polymeraze Chain Reaction (RT-PCR). Recombinants of PVY strains predominate among the isolates tested. Using one-step triplex RT-PCR most PVYN-Wi isolates were classified as subgroup PVYNWi-P and most PVYN and/or PVYNTN isolates as the recombinant PVYNTN strain. A recombinant PVYNTN isolate (12/94) and two additional PVYN and/or PVYNTN isolates were not detected by one-step triplex RT-PCR. Twelve isolates were identified as the PVYO strain but PVYN, non-recombinant PVYNTN and PVYC strains were not found. Serological and biological assays of 144 isolates of PVYN-Wi strain showed that 100 isolates were the expected PVYO serotype with vein necrosis (VN) symptoms on tobacco. However, 10 isolates of the PVYNWi-P subgroup exhibited vein clearing (VCl) on tobacco and 2 isolates of the PVYNN242 subgroup unexpectedly exhibited as the PVYN serotype. All the isolates of PVYN-Wi strain induced severe local lesions (LL) on Chenopodium amaranticolor. Out of 126 isolates of PVYNTN strain tested, 76 were typical PVYN serotype with VN on tobacco, but their reactions on C. amaranticolor were different: 13 isolates did not show symptoms, 23 isolates induced weak, and 40 isolates induced severe LL. The remaining isolates of PVYN-Wi, PVYN and/or PVYNTN or PVYO were serologically PVYN and PVYO positive or exhibited unpredictable serological and biological reactions.