Proline Dehydrogenase Contributes to Pathogen Defense in Arabidopsis

NICOLAS MIGUEL CECCHINI; MARIELA INES MONTEOLIVA; MARIA ELENA ALVAREZ

PLANT PHYSIOLOGY.

AMER SOC PLANT BIOLOGISTS

Lugar: Rockville; Año: 2011

0032-0889

L-Proline (Pro) catabolism is activated in plants recovering from abiotic stresses associated with water deprivation. In thiscatabolic pathway, Pro is converted to glutamate by two reactions catalyzed by proline dehydrogenase (ProDH) and D1-pyrroline-5-carboxylate dehydrogenase (P5CDH), with D1-pyrroline-5-carboxylate (P5C) as the intermediate. Alternatively,under certain conditions, the P5C derived from Pro is converted back to Pro by P5C reductase, thus stimulating the Pro-P5Ccycle, which may generate reactive oxygen species (ROS) as a consequence of the ProDH activity. We previously observed thatPro biosynthesis is altered in Arabidopsis (Arabidopsis thaliana) tissues that induce the hypersensitive response (HR) inresponse to Pseudomonas syringae. In this work, we characterized the Pro catabolic pathway and ProDH activity in this model.Induction of ProDH expression was found to be dependent on salicylic acid, and an increase in ProDH activity was detected incells destined to die. To evaluate the role of ProDH in the HR, ProDH-silenced plants were generated. These plants displayedreduced ROS and cell death levels as well as enhanced susceptibility in response to avirulent pathogens. Interestingly, the earlyactivation of ProDH was accompanied by an increase in P5C reductase but not in P5CDH transcripts, with few changesoccurring in the Pro and P5C levels. Therefore, our results suggest that in wild-type plants, ProDH is a defense componentcontributing to HR and disease resistance, which apparently potentiates the accumulation of ROS. The participation of the Pro-P5C cycle in the latter response is discussed.