Apoplastic polyamine oxidation plays different roles in local responses of tobacco to infection by the necrotrophic fungus Sclerotinia sclerotiorum and the biotrophic bacterium Pseudomonas viridiflava

MARINA M; MAIALE SJ; ROSSI FR; ROMERO FM; RIVAS EI; GÁRRIZ A; RUIZ OA; PIECKENSTAIN FL

PLANT PHYSIOLOGY.

Am Soc Plant Biol

Año: 2008 vol. 147 p. 2164 - 2178

0032-0889

The role of polyamine (PA) metabolism in tobacco (Nicotiana tabacum) defenseagainst pathogens with contrasting pathogenic strategies was evaluated. Infection bythe necrotrophic fungus Sclerotinia sclerotiorum resulted in increased argininedecarboxylase expression and activity in host tissues, as well as putrescine andspermine accumulation in leaf apoplast. Enhancement of leaf PA levels, either by usingtransgenic plants or infiltration with exogenous PAs, led to increased necrosis due toinfection by S. sclerotiorum. Specific inhibition of diamine and polyamine oxidases(DAO and PAO) attenuated the PA-induced enhancement of leaf necrosis duringfungal infection. When tobacco responses to infection by the biotrophic bacteriumPseudomonas viridiflava were investigated, an increase of apoplastic spermine levelswas detected. Enhancement of host PA levels by the above-described experimentalapproaches strongly decreased in planta bacterial growth, an effect that was blockedby a PAO inhibitor.It can be concluded that accumulation and further oxidation of free PAs in theleaf apoplast of tobacco plants occurs in a similar, although not identical way duringtobacco defense against infection by microorganisms with contrasting pathogenesisstrategies. This response affects pathogen's ability to colonize host tissues and resultsdetrimental for plant defense against necrotrophic pathogens that feed on necrotictissue and, on the contrary, plays a beneficial role in defense against biotrophicpathogens that depend on living tissue for successful host colonization. Thus,apoplastic PAs play important roles in plant-pathogen interactions, and modulation ofhost PA levels, particularly in the leaf apoplast, may lead to significant changes in hostsusceptibility to different kinds of pathogens.