Page 139 - PC2019 Program & Proceedings

PLANT CANADA 2019

S63. Resource independent plant competition alters ROS levels, antioxidant status and
susceptibility to cell death in Arabidopsis thaliana
*
Berardi, N. ; S. Amirsadeghi; C. Swanton
University of Guelph

Changes in light quality induced by the presence of neighbouring vegetation is an important mechanism
of plant competition. Alteration of the light environment is recognized via changes in the red to far-red
light ratio (R/FR), in which a reduction in R/FR is induced by light that is reflected horizontally off
neighbouring vegetation. Recognition of a reduced R/FR elicits physiological stress responses within the
plant characterized by increased reactive oxygen species (ROS) production and subsequent modification
of antioxidant capacity to regulate ROS levels. Previous research suggests that as ROS levels rise, they
may elicit a signalling event within the plant causing a distinct set of genes to be up- or down- regulated
which is specific to each individual ROS. To further explore the mechanisms surrounding plant
competition and ROS signalling, Arabidopsis thaliana was studied under two light environments: a high
R/FR (weed-free) environment and a low R/FR (weedy) environment. Results indicate that ROS levels
and subsequently, antioxidant status are altered in response to far-red enriched light. The results also
suggest that key ROS are involved in the physiological stress response to low R/FR and that signalling
events of various ROS may be competing. Further identification of these responses would not only
provide important insights into the molecular basis of plant competition, but may also provide support for
theories that suggest the competitive nature of ROS signalling.

Nicole Berardi (nberardi@uoguelph.ca)

S64. Metabolism of reactive oxygen and nitrogen species during anoxic stress and reaeration in
tobacco plants differentially expressing alternative oxidase
1
*1
2
Jayawardhane, J. ; A. Igamberdiev ; G.C. Vanlerberghe
1 Memorial University of Newfoundland
2 University of Toronto Scarborough
Flooding and waterlogging create low oxygen conditions in plants limiting mitochondrial respiration and
oxidative phosphorylation while reaeration after receding of water elevates the oxidative damage. Leaves
of wild type and transgenic tobacco (Nicotiana tabacum L. cv Petit Havana SR1) plants differentially
expressing alternative oxidase (AOX) were used to investigate the role of AOX during anoxia and post-
anoxia in comparison to normal air conditions. ATP/ADP ratio decreased during anoxia and increased
during reaeration. AOX overexpressing lines showed higher ATP/ADP ratio in each condition as
compared to other plant lines. Nitric oxide production was higher in AOX overexpressing lines during
anoxia. S-nitrosylation was higher in knockdown lines under each condition and the levels increased
during reaeration in both lines. The levels of reactive oxygen species and lipid peroxidation were higher
in anoxia and during post-anoxia. However, those levels were lower in AOX overexpressing lines. The
activities of catalase and SOD increased during anoxia and reaeration. Levels of SOD were higher in
AOX knockdown lines while catalase activity was higher in AOX overexpressing lines. Ascorbate
peroxidase activity followed a similar pattern as catalase. Glutathione reductase activity decreased during
anoxia and increased during reaeration. Other enzymes of the ascorbate-glutathione cycle varied
differently during anoxia and post-anoxia depending on AOX expression. It is concluded that AOX has a
protective effect on cellular energy level and oxidative damage during anoxia and reaeration.

Jayamini Jayawardhane (jjayawardhan@mun.ca)

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