Tobacco susceptibility to Potato virus YNTN infection is affected by grafting and endogenous cytokinin content

Spoustová P., Hýsková V., Müller K., Schnablová R., Ryšlavá H., Čeřovská N., Malbeck J., Cvikrová M., Synková H.
PLANT SCIENCE 235: 25-36, 2015

Keywords: Cytokinin, ipt gene, Antioxidant system, Salicylic acid, Peroxidase, Malic enzyme
Abstract: Faster or stronger response to pathogen occurs if plants undergo prior priming. Cytokinins seem to bealso involved in plant priming and in response to pathogens. Susceptibility to Potato virus YNTN(PVYNTN)was studied in transgenic cytokinin overproducing (Pssu-ipt) tobacco and compared with nontransgenicplants. Since cytokinin overproduction inhibits development of plant roots and grafting overcomes thislimitation, both types were grown as rooted and/or grafted plants to check also the effect of grafting.Control rooted tobacco (C), the most susceptible to PVYNTN, showed always symptoms during the infectiontogether with the rising virus content and a systemic response, such as accumulation of H2O2, salicylicacid (SA) and other phenolic acids, and stress-induced enzyme activities. In transgenic and grafted plants,the response to PVYNTNwas dependent on protective mechanisms activated prior to the inoculation. In Pssu-ipt tobacco, cytokinin active forms and SA contents exceeded manifold their content in C. Graftingpromoted the accumulation of phenolics, but SA, and stimulated peroxidase activities. Thus, the pre-infection barrier established in both transgenic and grafted plants helped to suppress partly the virusmultiplication and resulted in milder symptom development. However, only the synergic effect of both grafting and the high cytokinins led to PVYNTNtolerance in transgenic grafts. Possible mechanisms were discussed.
IEB authors: Noemi Čeřovská, Milena Cvikrová, Jiří Malbeck, Karel Müller, Renáta Schnablová, Petra Spoustová, Helena Synková