A Turnip mosaic virus determinant of systemic necrosis in Nicotiana benthamiana, and a novel resistance-breaking determinant in Chinese cabbage identified from chimeric infectious clones

Authors: KIM, IK-HYUN - Chungnam National University; JU, HYEK-YOUNG - Chungnam National University; GONG, JUNSU - Chungnam National University; HAN, JAE-YEONG - Chungnam National University; SEO, EUN-YOUNG - Chungnam National University; CHO, SANG-WON - Chungnam National University; HU, WEN-XING - Chungnam National University; CHOI, SU-RYUN - Chungnam National University; LIM, YOUNG PYO - Chungnam National University; Domier, Leslie; Hammond, John; LIM, HYOUN-SUB - Chungnam National University

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/24/2019
Publication Date: 5/2/2019
Citation: Kim, I., Ju, H., Gong, J., Han, J., Seo, E., Cho, S., Hu, W., Choi, S., Lim, Y., Domier, L.L., Hammond, J., Lim, H. 2019. A Turnip mosaic virus determinant of systemic necrosis in Nicotiana benthamiana, and a novel resistance-breaking determinant in Chinese cabbage identified from chimeric infectious clones. Phytopathology. 109:1638-1647. https://doi.org/10.1094/phyto-08-18-0323-r.
DOI: https://doi.org/10.1094/phyto-08-18-0323-r

Interpretive Summary: Plant viruses reduce yield and quality in many crops, and may be spread though seed, mechanical transmission, or vectored transmission. Turnip mosaic virus (TuMV) has a wide host range, including ornamental crops and many vegetable crops. Several resistance genes are available in various brassicaceous crops, including turnip, cabbage and radish, but new viral isolates periodically emerge which can overcome resistance genes. Therefore new resistance genes must be identified to maintain crop yields and quality. Korean scientists collaborated with ARS scientists to study two isolates of TuMV that cause differential reactions in three host species. A viral gene associated with severe symptoms in one host was identified. In addition, a Chinese cabbage variety that is resistant to most TuMV isolates was found to be susceptible to infection by one viral construct. The presumed viral determinant of infectivity was identified. Use of diverse isolates of TuMV to screen crop germplasm may allow identification of new host resistance genes for breeders to utilize for sustainable crop yields.

Technical Abstract: Infectious clones of two Korean isolates of Turnip mosaic virus, KIH1 and HJY1 show severe and mild symptoms, respectively, in Nicotiana benthamiana. Infectious clones under control of both 35S and T7 promoters allow infection by either agroinfiltration or in vitro transcripts; chimeric constructs were used to localize the major determinant of symptom severity in N. benthamiana. KIH1 and chimeras KHH and KKH induced systemic necrosis, whereas HJY1 and chimeras HHK, HKK, and HKH induced mild symptoms, indicating that the determinant of necrosis was within the N-terminal 3.9 kb of KIH1; amino acid identities of P1, HC-Pro, P3, 6K1, and the CI N-terminal domain were 90.06%, 98.91%, 93.80%, 100%, and 100% respectively. Expression of either P1 or P3 from a Potato virus X vector yielded symptom differences only between P3 of KIH1 and HJY1, demonstrating a role of P3 in symptom severity in N. benthamiana. Whereas neither KIH1 nor HJY1 were able to infect Brassica rapa var. pekinensis cv. Norang, chimera KKH was virulent on this otherwise TuMV-resistant genotype, suggesting that two TuMV determinants are required to overcome the resistance. Diverse TuMV isolates, chimeras, and recombinants may also overcome resistance in commercial breeding lines, and allow identification of additional resistance genes.