Broad-spectrum resistance to distinct tospoviruses in transgenic tobacco carrying the conserved region of the L protein of Watermelon silver mottle virus
Yeh S-D, Chen T-C, Peng J-C, Liu F-L, Wu Y-L
Department of Plant Pathology, National Chung Hsing University, Taichung, 40227, Taiwan.
Correspondence: sdyeh@nchu.edu.tw
Comparison of the deduced L proteins among tospoviruses revealed that the region containing reported motifs of RNA-dependent RNA polymerase (RdRp) is conserved. Accordingly, the DNA fragment corresponding to the conserved region (nts 3975¨C4928) of the viral complementary strand of L RNA of Watermelon silver mottle virus (WSMoV), the type member of the WSMoV serogroup, was cloned and modified as a translatable construct WLm in an Agrobacterium binary vector. In addition, duplicated stop codons or stop codons plus frame shift were added at the upstream of the conserved motifs region to generate untranslatable constructs WLmt and WLmts, respectively. Antisense and inverted repeat of the conserved region were also constructed and denoted WLmAs and WLmds, respectively. Transgenic lines of Nicotiana benthamiana carrying individual constructs were evaluated against tospoviruses under greenhouse conditions. In addition to WSMoV, other distinct tospoviruses including Tomato spotted wilt virus (TSWV), Groundnut ringspot virus (GRSV), Impatiens necrotic spot virus (INSV), and Peanut chlorotic fan-spot virus (PCFV) were used for assay. WLm, WLmt, WLmts, WLmAs, and WLmds transgenic lines showed various degrees of resistance against WSMoV, with 48.3% (14 out of 29 lines assayed), 55% (11/20), 60% (9/15), 66.7% (20/30), and 74.1% (20/27) lines, respectively. Among the lines resistant to WSMoV, there were 5 WLm lines, 4 WLmt lines, 1 WLmts line, 9 WLmAs lines, and 14 WLmds lines were resistance to TSWV; 1 WLmt line, 2 WLmAs lines, and 5 WLmds lines were resistant to GRSV; 1 WLmt line, 2 WLmAs lines, and 3 WLmds lines were resistant to INSV; and 1 WLmt line, 3 WLmAs lines, and 4 WLmds lines were resistant to PCFV. Moreover, 1 WLmt line was highly resistant to all five tospoviruses. Our results indicated that transgenic tobacco lines carrying the RdRp conserved region provide broad-spectrum resistances to different tospoviruses. This approach is being applied for economic crops, such as melon and tomato, for the control of different tospoviruses.
