Proline Accumulation and AtP5CS2 Gene Activation Are Induced by Plant-Pathogen Incompatible Interactions in Arabidopsis

GEORGINA FABRO; IZABELLA KOVÁCS; VALERIA PAVET; LÁSZLÓ SZABADOS; MARÍA E. ALVAREZ

MOLECULAR PLANT-MICROBE INTERACTIONS

AMER PHYTOPATHOLOGICAL SOC

Lugar: Saint Paul, Minessota, USA; Año: 2004 vol. 17 p. 343 - 350

0894-0282

Accumulation of free L-proline (Pro) is a typical stressresponse incited by osmotic injuries in plants and microorganisms.Although the protective role of Pro in osmoticstress is not well understood, it is thought to function ascompatible osmolyte or as a scavenger of reactive oxygenspecies (ROS). Here we show that, in Arabidopsis thaliana,Pro biosynthesis can be activated by incompatible plant?pathogen interactions triggering a hypersensitive response(HR). Pro accumulates in leaf tissues treated with Pseudomonassyringae pv. tomato avirulent strains (avrRpt2 andavrRpm1) but remains unchanged in leaves infected withisogenic virulent bacteria. Incompatible interactions leadto transcriptional activation of AtP5CS2, but not AtP5CS1,encoding the rate limiting enzyme in Pro biosynthesis pyrroline-5-carboxylate synthase (P5CS). AtP5CS2:GUS andAtP5CS2:LUC transgenes were induced inside and aroundthe HR lesions produced by avirulent Pseudomonas spp. intransgenic plants. Pro accumulation was faster andstronger when stimulated by avrRpm1 than by avrRpt2,and was compromised in the low-salicylic acid plantsNahG and eds5 when signaled through the RPS2-dependentpathway. In addition, Pro content and AtP5CS2 expressionwere enhanced by ROS in wild-type plants, suggestingthat ROS may function as an intermediate signal inAtP5CS2-mediated Pro accumulation.