Proline Dehydrogenase Contributes to Pathogen Defense in Arabidopsis      

Abstract

l-Proline (Pro) catabolism is activated in plants recovering from abiotic stresses associated with water deprivation. In this catabolic pathway, Pro is converted to glutamate by two reactions catalyzed by proline dehydrogenase (ProDH) and Ɗ1-pyrroline-5-carboxylate dehydrogenase (P5CDH), with Ɗ1-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-P5C cycle, which may generate reactive oxygen species (ROS) as a consequence of the ProDH activity. We previously observed that Pro biosynthesis is altered in Arabidopsis (Arabidopsis thaliana) tissues that induce the hypersensitive response (HR) in response 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 in cells destined to die. To evaluate the role of ProDH in the HR, ProDH-silenced plants were generated. These plants displayed reduced ROS and cell death levels as well as enhanced susceptibility in response to avirulent pathogens. Interestingly, the early activation of ProDH was accompanied by an increase in P5C reductase but not in P5CDH transcripts, with few changes occurring in the Pro and P5C levels. Therefore, our results suggest that in wild-type plants, ProDH is a defense component contributing 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.

Changes in antioxidant systems in sunflower partial resistant and susceptible lines as affected by Sclerotinia sclerotiorum

“…High proline accumulation in diseased tissue probably is due to pathological disorders (Smimoff & Cumbes 1989). Cecchini et al (2011) showed that L-proline catabolism is activated in plants during recovering process.…”

Pipecolic acid enhances resistance to bacterial infection and primes salicylic acid and nicotine accumulation in tobacco

“…[7][8][9] In addition, the oxidation of Argand/or Orn-derived polyamines and the metabolism of Pro contribute to the production of reactive oxygen species and to the development of hypersensitive cell death following elicitor treatment or inoculation with avirulent bacteria. 10,11 Further, the formation of acetylated amino acids and phytohormone-amino acid conjugates can mediate or negatively regulate plant defense signaling and pathogen resistance. [12][13][14] Also, enhanced production of particular amino acids can directly impact plant resistance to specific pathogen types.…”

Reduced Carbohydrate Availability Enhances the Susceptibility of Arabidopsis toward Colletotrichum higginsianum

“…It has been shown that several enzymes of plant primary metabolism, Glc-6-P dehydrogenase (Scharte et al, 2005), malic enzyme Voll et al, 2012), and Pro dehydrogenase (Cecchini et al, 2011), provide the cytosol with reducing equivalents that are required for the effective production of reactive oxygen species and can directly support induced plant defenses with reducing power. In addition, several reports reinforce the ideas that (1) the balance between extracellular Suc and hexose is perceived by the host (Biemelt and Sonnewald, 2006, and refs.…”