The fact that single immune receptors conferring multiple resistances to taxonomically unrelated pathogens may not be exceptional gives plant breeders a strong incentive to identify and to use common virulence targets as leads to discover broad-specificity resistance genes:
Dual disease resistance mediated by the immune receptor Cf-2 in tomato requires a common virulence target of a fungus and a nematode. PNAS USA 06 June 2012 doi: 10.1073/pnas.1202867109 Plants lack the seemingly unlimited receptor diversity of a somatic adaptive immune system as found in vertebrates and rely on only a relatively small set of innate immune receptors to resist a myriad of pathogens. Here, we show that disease-resistant tomato plants use an efficient mechanism to leverage the limited nonself recognition capacity of their innate immune system. We found that the extracellular plant immune receptor protein Cf-2 of the red currant tomato (Solanum pimpinellifolium) has acquired dual resistance specificity by sensing perturbations in a common virulence target of two independently evolved effectors of a fungus and a nematode. The Cf-2 protein, originally identified as a monospecific immune receptor for the leaf mold fungus Cladosporium fulvum, also mediates disease resistance to the root parasitic nematode Globodera rostochiensis pathotype Ro1-Mierenbos. The Cf-2–mediated dual resistance is triggered by effector-induced perturbations of the apoplastic Rcr3pim protein of S. pimpinellifolium. Binding of the venom allergen-like effector protein Gr-VAP1 of G. rostochiensis to Rcr3pim perturbs the active site of this papain-like cysteine protease. In the absence of the Cf-2 receptor, Rcr3pim increases the susceptibility of tomato plants to G. rostochiensis, thus showing its role as a virulence target of these nematodes. Furthermore, both nematode infection and transient expression of Gr-VAP1 in tomato plants harboring Cf-2 and Rcr3pim trigger a defense-related programmed cell death in plant cells. Our data demonstrate that monitoring host proteins targeted by multiple pathogens broadens the spectrum of disease resistances mediated by single plant immune receptors.
And there is also the recent work showing that plants can pass acquired defenses against pests and pathogens on to their offspring: Memory Tools for Plants – how plants pass defenses to offspring through a complex molecular network
Plants are clearly a lot smarter than many people give them credit for. The question is, are we smart enough to use these new discoveries to help feed ourselves in the future?