Study of the photosynthetic responce to drought stress in AOX mutants of Arabidopsis thaliana
Year: 2009
Type: dissertation
Abstract: Plant metabolism is modulated in a very dynamic way, being dependent on environmental factors. The integration between photosynthesis and respiration is a key-aspect of metabolic regulation. Photorespiration may play an important role on the integration of chloroplastidial and mitochondrial metabolism, as photorespiratory NADH might be oxidized in the respiratory chain by internal type II NAD(P)H dehydrogenases and alternative oxidase (AOX). This work aims to test the role of AOX in the mitochondrial redox potential dissipation that occurs during photosynthesis and photorespiration under water stress. The hypothesis is that AOX plays an important role and its lower activity will reflect itself in photosynthesis and photorespiration. For that, wild type (Col-0) Arabidopsis and AOX1a transgenic Arabidopsis (AS-AOX1a) were used. No morphological differences were found between the two lines of plants under control or stress conditions. However, higher Specific Leaf Area and stomatal conductance were observed in the transgenic plants under mild stress, whereas their water potential was lower. A more pronounced decrease in photorespiration with drought in AS-AOX1a plants was also detected, having reflected itself in the photorespiration / photosynthesis ratio, which was lower in these plants. The observed decrease in ETR and qP might indicate that the quinone pool had became more reduced in both lines of plants, but the curvilinear decrease on AS-AOX1a contrasts with the linear trend in Col-0, suggesting differences on the dynamics of stress sensing and response. A very highly significant increase of NPQ under stress was found on AS-AOX1a plants, in contrast with Col-0 plants, where the increase was much less sensible, suggesting an increase on the activity of alternative energy dissipating mechanisms on the former, which is in accordance with lower photorespiration rates. Lower amounts of GDC-P1 and UCP1 transcripts were detected in AS-AOX1a, which is also in agreement with the lower photorespiration rate in these plants. In contrast, the SHMT transcripts increased with drought stress in both plant lines and were higher in AS-AOX1a. All together the results suggest that the AS plants AS being impaired in the expression of AOX1a display alterations in the photorespiratory process.
Author: João L. Coito
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
SDG: Zero hunger
Open Access status: green
OpenAlex ID: W2246522392