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An h-Type Thioredoxin Functions in Tobacco Defense Responses to Two Species of Viruses and an Abiotic Oxidative Stress

November 2010 , Volume 23 , Number  11
Pages  1,470 - 1,485

Lijun Sun,1,2 Haiying Ren,1,3 Ruoxue Liu,1 Baoyan Li,1 Tingquan Wu,1 Feng Sun,1 Huimin Liu,1 Xiaomeng Wang,1 and Hansong Dong1

1Ministry of Agriculture of R. P. China Key Laboratory of Monitoring and Management of Crop Pathogens and Insect Pests, Nanjing Agricultural University, Nanjing, 210095, China; 2Nanjing Institute for Comprehensive Utilization of Wild Plants, Nanjing, 210042, China; and 3Institute of Plant Protection and Microbiology, Zhejiang Academy of Agricultural Sciences, Hangzhou, 310021, China

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Accepted 7 July 2010.

Various thioredoxin (Trx) proteins have been identified in plants. However, many of the physiological roles played by these proteins remain to be elucidated. We cloned a TRXh-like gene predicted to encode an h-type Trx in tobacco (Nicotiana tabacum) and designated it NtTRXh3, based on the biochemical activity of the NtTRXh3 protein. Overexpression of NtTRXh3 conferred resistance to Tobacco mosaic virus and Cucumber mosaic virus, both of which showed reduced multiplication and pathogenicity in NtTRXh3-overexpressing plants compared with controls. NtTRXh3 overexpression also enhanced tobacco resistance to oxidative stress induced by paraquat, an herbicide that inhibits the production of reducing equivalents by chloroplasts. The NtTRXh3 protein localized exclusively to chloroplasts in coordination with the maintenance of cellular reducing conditions, which accompanied an elevation in the glutathione/glutathione disulfide couple ratio. NtTRXh3 gene expression and NtTRXh3 protein production were necessary for these defensive responses, because they were all arrested when NtTRXh3 was silenced and the production of NtTRXh3 protein was abrogated. These results suggest that NtTRXh3 is involved in the resistance of tobacco to virus infection and abiotic oxidative stress.

© 2010 The American Phytopathological Society