The role of PTOX in the acclimation of alpine plants to extreme conditions

• Main Author: Laureau, Constance
• Other Authors: Ecologie Systématique et Evolution (ESE), Université Paris-Sud - Paris 11 (UP11)-AgroParisTech-Centre National de la Recherche Scientifique (CNRS), Université Paris Sud - Paris XI, Peter Streb
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2012
• Subjects: Stress tolerance; PTOX; Alpine plants; Glutathione; Antioxidants; Photorespiration; Tolérance au stress; Antioxydants; Glutathion; Plantes alpines; [SDV.SA]Life Sciences [q-bio]/Agricultural sciences; Ranunculus glacialis
• Online Access: https://theses.hal.science/tel-01022824; https://theses.hal.science/tel-01022824/document; https://theses.hal.science/tel-01022824/file/VA2_LAUREAU_CONSTANCE_10072012.pdf

The alpine climate above 2400 meters altitude shows large variations in temperature and very important light intensity (3000 µmol photons m-2 s-1), which are known to generate a state of significant reduction in the photosynthetic electron transport chain. The proper functioning of the photosynthetic process is essential for vascular plants species that are present in this alpine environment and must complete their life cycle within a very short growing season.Soldanella alpina and Ranunculus glacialis are two species restricted to alpine and snow floors. In their natural growth environment we measured very low (0.7 ° C) and high temperature (37 ° C) under lights above 2500 µmol photons m-2 s-1. Among non-alpine species such conditions induce photoinhibition of PSII, which is avoided in S. alpina and R. glacialis, by very different mechanisms. Antioxidant systems and non-photochemical quenching are particularly important in S. alpina. In Ranunculus glacialis, photorespiration remains very important and a high content of PTOX is described. The roles of antioxidants and PTOX in photoprotection of both species were studied.In one part of the thesis, we showed that a decrease in antioxidant capacity by reducing the concentration of glutathione does not affect tolerance to low-temperature photoinhibition. In the second part the results imply that overexpression of PTOX in tobacco enhances photoinhibition by strong light to produce reactive oxygen species.Using different environmental conditions for Ranunculus glacialis growth, we showed that expression of the PTOX is induced by strong light, but not by low temperatures. With an approach combining gas exchange measurements and chlorophyll fluorescence measurements, we showed that an electron flow to oxygen, independent of photorespiration, correlated with the presence of PTOX. Through measures of chlorophyll fluorescence in the presence of various inhibitors photosynthetic, we could show that the importance of this electron flow to oxygen correlates with the amount of ...