|Li, Qi - UNIV OF CALIF-RIVERSIDE|
|Xie, Qi-Guang - UNIV OF CALIF-RIVERSIDE|
|Smith-Becker, Jennifer - UNIV OF CALIF-RIVERSIDE|
|Kaloshian, Isgouhi - UNIV OF CALIF-RIVERSIDE|
Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 5, 2006
Publication Date: June 1, 2006
Citation: Li, Q., Xie, Q., Smith-Becker, J., Navarre, D.A., Kaloshian, I. 2006. Mi-1 mediated aphid resistance involves salicylic acid and mitogen-activated protein kinase signaling cascades. Plant Physiology. 19(6):655-664. Interpretive Summary: This work showed that salicylic acid plays a major role in resistance to potato aphid conferred by the Mi-1 gene. Resistant plants that lost the ability to accumulate salicylic acid became completely susceptible to potato aphid. This work also shows that proteins called MAP kinases are also involved in the resistance response to potato aphid. These results further demonstrate that plant resistance to piercing-sucking insects is similar to that against other plant pathogens.
Technical Abstract: The tomato (Solanum esculentum L.) Mi-1 gene confers resistance to three distinct organisms root-knot nematodes, potato aphids and whiteflies. Resistance to potato aphid, Macrosiphum euphorbiae (Thomas), is developmentally regulated and is not associated with induction of a hypersensitive response. The nahG transgene that eliminates endogenous SA was used to test the role of the salicylic acid (SA) signaling pathway in the resistance mediated by Mi-1 to potato aphids. NahG tomato plants exhibited increased susceptibility to potato aphid infestations compared to wild type tomato. In contrast, aphid reproduction was not affected by the presence of the nahG transgene. Aphid resistance in Mi-1 NahG plants was completely abolished and the phenotype was successfully rescued by application of BTH indicating that SA signaling pathway is an important component of Mi-1-mediated aphid resistance. Using virus-induced gene silencing, we identified a mitogen-activated protein kinase (MAPK) cascade that is also required for Mi-1-mediated aphid resistance. Silencing plants for MAPK kinase, LeMKK2, and MAPKs, LeMPK2 and LeMPK1, or LeMPK3 resulted in attenuation of Mi-1-mediated aphid resistance. These results further demonstrate that resistance gene-mediated signaling events against piercing-sucking insects are similar to those against other plant pathogens.