engleski

Salicylic acid contributes to basal defense of Solanum tuberosum against potato spindle tuber viroid (PSTVd)

Viroids are small, circular, noncoding RNAs currently known to infect only plants. Potato spindle tuber viroid (PSTVd), the type species of Pospiviroidae, is the most important subviral pathogen of potato that can severely limit potato crop yields. Unlike plant resistance to most other pathogens, no naturally occurring resistance to PSTVd has been detected in potato cultivars. The ability of viroids to cause disease is determined by molecular interactions between the host plant and the viroid RNA. These interactions directly affect the development of symptoms and host plant defense responses, in which the signaling compound salicylic acid (SA) plays a key role. To evaluate the role of SA in the potato-PSTVd compatible interaction, we used transgenic NahG potato plants that are unable to accumulate SA. When challenged with PSTVd, NahG transgenic lines showed pronounced symptom development such as stunted growth, necrosis of old leaves, and reduction in the size of young leaves and tubers. The dynamics of viroid replication and the expression of host genes, which are markers of defense responses, were followed in a time-course experiment during symptom development using real-time PCR. At 4 and 5 wpi, viroid RNA levels were significantly higher in infected leaves of NahG plants compared with wild-type plants, indicating delayed viroid accumulation in the wild-type plants. At 6 wpi, this difference in viroid replication between genotypes disappeared, suggesting that SA plays a role in the early phase of PSTVd infection of potato. The increased susceptibility of NahG plants correlated with the accumulation of reactive oxygen species (ROS), including hydrogen peroxide, impaired callose formation, and decreased expression of genes involved in SA - regulated basal defense responses, such as the pathogenesis-related genes PR -1 and PR -2. The obtained results suggest that SA is an important compound required for basal defense of potato against PSTVd.

PSTVd ; salicylic acid ; potato (Solanum tuberosum L.)

nije evidentirano