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Suppression of Reactive Oxygen Species and Enhanced Stress Tolerance in Rubia cordifolia Cells Expressing the rolC Oncogene

December 2008 , Volume 21 , Number  12
Pages  1,561 - 1,570

Victor P. Bulgakov,1 Dmitry L. Aminin,2 Yuri N. Shkryl,1 Tatiana Y. Gorpenchenko,1 Galina N. Veremeichik,1 Pavel S. Dmitrenok,2 and Yuri N. Zhuravlev1

1Institute of Biology and Soil Science, and 2Pacific Institute of Bioorganic Chemistry, Far East Branch of the Russian Academy of Sciences, Vladivostok 690022, Russia

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Accepted 23 July 2008.

It is known that expression of the Agrobacterium rhizogenes rolC gene in transformed plant cells causes defense-like reactions, such as increased phytoalexin production and expression of pathogenesis-related proteins. In the present study, we examined whether this phenomenon is associated with increased production of reactive oxygen species (ROS). Single-cell assays based on confocal microscopy and fluorogenic dyes (2,7-dichlorofluorescein diacetate and dihydrorhodamine 123) showed reduced steady-state levels of ROS in rolC-expressing Rubia cordifolia cells as compared with normal cells. Paraquat, a ROS inducer, caused significant ROS elevation in normal cells but had little effect on rolC-transformed cells. Likewise, ROS elevation triggered by a light stress was suppressed in transformed cells. Our results indicate that the rolC gene acts as a ROS suppressor in unstressed cells and its expression prevents stress-induced ROS elevations. We detected a two- to threefold increase in tolerance of rolC-transformed cells to salt, heat, and cold treatments. Simultaneously, rolC-transformed cells maintained permanently active defensive status, as found by measuring isochorismate synthase gene expression and anthraquinone production. Thus, the oncogene provoked multiple effects in which ROS production and phytoalexin production were clearly dissociated.

Additional keyword:defense reactions.

© 2008 The American Phytopathological Society