Abstract
Plants coordinate their responses to various biotic and abiotic stresses in order to optimize their developmental and acclimatory programmes. The ultimate response to an excessive amount of stress is local induction of cell death mechanisms. The death of certain cells can help to maintain tissue homeostasis and enable nutrient remobilization, thus increasing the survival chances of the whole organism in unfavourable environmental conditions. UV radiation is one of the environmental factors that negatively affects the photosynthetic process and triggers cell death. The aim of this work was to evaluate a possible role of the red/far-red light photoreceptors phytochrome A (phyA) and phytochrome B (phyB) and their interrelations during acclimatory responses to UV stress. We showed that UV-C treatment caused a disturbance in photosystem II and a deregulation of photosynthetic pigment content and antioxidant enzymes activities, followed by increased cell mortality rate in phyB and phyAB null mutants. We also propose a regulatory role of phyA and phyB in CO2 assimilation, non-photochemical quenching, reactive oxygen species accumulation and salicylic acid content. Taken together, our results suggest a novel role of phytochromes as putative regulators of cell death and acclimatory responses to UV.
Highlights
In the natural environment, plant growth and development have developed the ability to perceive and react to both sudare challenged by ceaseless fluctuations of numerous factors. den and seasonal changes
Since phytochrome B (phyB) and phyAB Arabidopsis mutants display a constitutive shade-avoiding phenotype characterized by elongated petioles (Reed et al, 1993) (Fig. 1), all the measured parameters were recalculated taking into consideration the rosette area
After UV treatment, most dark blue spots, which are the signs of dead cells, were present in lsd1 mutant. phyB and phyAB mutants showed the high level of dead cells, which was consistent with the electrolyte leakage results
Summary
Plant growth and development have developed the ability to perceive and react to both sudare challenged by ceaseless fluctuations of numerous factors. den and seasonal changes. Active mechanisms of light perception that are dependent on photoreceptors (Karpiński et al, 2003; Chen et al, 2004; Möglich et al, 2010; Chen and Chory, 2011) and photosystems (Szechyńska-Hebda et al, 2010). These mechanisms allow plants to sense changes in both, the spectrum and intensity of light. The most intensively studied plant photoreceptors are phytochromes, which are able to absorb red and far-red light. By direct interaction with PIFs, phytochromes induce their detachment from DNA and promote their degradation by the 26S proteasome (Park et al, 2004, 2012)
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