Construction of full-length infectious clones of turnip mosaic virus isolates infecting Perilla frutescens and genetic analysis of recently emerged strains in Korea

Abstract

Perilla is an annual herb with a unique aroma and taste that has been cultivated in Korea for hundreds of years. It has been widely cultivated in many Asian and European countries as a food and medicinal crop. Recently, several viruses have been reported to cause diseases in perilla in Korea, including turnip mosaic virus (TuMV), which is known as a brassica pathogen due to its significant damage to brassica crops. In this study, we determined the complete genome sequences of two new TuMV isolates originating from perilla in Korea. Full-length infectious cDNA clones of these two isolates were constructed, and their infectivity was tested by agroinfiltration of Nicotiana benthamiana and sap inoculation of Chinese cabbage and radish plants. In addition, we analyzed the phylogenetic relationship of six new Korean TuMV isolates to members of the four major groups. We also used RDP4 software to conduct recombination analysis of recent isolates from Korea, which provided new insight into the evolutionary relationships of Korean isolates of TuMV. Supplementary Information The online version contains supplementary material available at 10.1007/s00705-021-05356-9.

A single amino acid substitution in the conserved CDNQLD motif causes both differences in RNA silencing suppression activity of the turnip mosaic virus HC-Pro protein and variations in symptom severity

“…Binary vector pJY and full-length PCR products were digested with the same restriction enzymes [30]. After ligation, two full-length cDNA clones were obtained, named KJS 5 and KJS 5 − 1, and transformed into Agrobacterium tumefaciens strain GV2260 [29]. Agroin ltration and sap inoculation of N. benthamiana and R. sativus were used to investigate their pathogenicity and symptoms [7].…”

“…Infectious cDNA clones were constructed from total RNAs extracted [29] from the leaves of R. sativus, collected in 2021 from Gangwon-do, Korea showing mild mosaic symptoms. Full-length cDNAs were synthesized by RT-PCR using TuMV terminal sequence-speci c primers containing restriction enzyme sites [7].…”

“…In prior reports, the CDN motif was associated with symptoms and RNA silencing suppression activity [28]. We previously conducted a phylogenetic analysis of complete aa sequences of many TuMV isolates, all of which had the conserved CDNQ 200 LD motif [29]. Variant KJS 5 of this work had the typical CDNQ 200 LD motif, and showed mild mosaic symptoms, while KJS 5 − 1 had the mutated CDNR 200 LD motif, and showed severe mosaic and malformation symptoms in radish.…”

“…Pentapeptide insertion into the HC-Pro of plum pox virus (PPV) resulted in insertion of LRPHQ after the Q residue of the motif, in effect yielding CDNQLR 202 , with silencing suppression activity equivalent to the wildtype CDNQLD 202 [28,39]. It has also been noted that more than one motif of HC-Pro can affect e ciency of RNA silencing suppression and symptom expression [28, 29,40].…”