Novel H2O2 signal transduction in plant cells:  Spatial dependency at the subcellular level

Wednesday, November 29 at 11 a.m.
Lynn Margulis seminar room, PABS building, INRAE Occitanie-Toulouse center.

https://inrae-fr.zoom.us/j/94085783482?pwd=VGk4N3FlMFk0Y2ZsR2Y3UHhlRTN2QT09 
Meeting ID : 940 8578 3482 
Secret code : PMlabex23! 

Abstract

All aerobic organisms are challenged by reactive oxygen species (ROS), which are a bi-product of processes such as respiration and photosynthesis. ROS promote oxidative stress, which is highly deleterious to cells, but such ROS are also potent signalling molecules. Consequently, ROS are important in a whole range of responses from the control of developmental processes, tumour formation and responses to environmental stress and as hormone secondary messengers. There is a very active field of research to understand how these conflicting roles are reconciled and to define the underpinning complex signalling routes and networks in a range of experimental systems.

During exposure to high light intensities (HL) that promote varying degrees of inhibition of photosynthesis (photoinhibition), chloroplasts signal to nuclei to induce a range of cellular responses. Photoinhibition is caused by increased oxidative damage to the photosynthetic apparatus. The rate of production of a mix of ROS, exemplified by hydrogen peroxide (H2O2) and singlet oxygen (1O2), may determine precisely how cells respond. This could range from induction of stress acclimation to triggering programmed cell death and is reflected in differing transcriptome profiles with one type of ROS or another. More recently, my lab used the H2O2 fluorescent protein (FP) biosensor HyPer in HL-exposed abaxial epidermal cells of Nicotiana benthamiana to establish that there was accumulation of H2O2 in nuclei that had originated from their associated chloroplasts and did not transit the cytosol to arrive at its destination. It was proposed that this spatial component provides signalling specificity for H2O2 under these conditions. However, little is known about the distribution of lipid hydroperoxides (LOOH) formed, for example, from oxidised polyunsaturated fatty acids, which are likely to be caused by increased production of 1O2 in chloroplasts suffering oxidative stress. We designed and constructed a new GFP-based ‘redox relay’ FP biosensor, roGFP2-synOrp1, which in combination with the widely used roGFP2-Orp1, allows by comparative imaging, a non-invasive dynamic quantification, which revealed different subcellular spatial distribution of LOOH and H2O2 during photo-oxidative stress.

The above examples are part of a wider consideration of the growing recognition of the importance of space as a dimension in the way ROS signalling is organised and how this lead to a realisation that there may be a distinct, plant cell-specific additional H2O2 signalling pathway for retrograde signalling that is superimposed on a wider signalling system network conserved across the Eukarya. This concept informs the basis of my current research. 

Contact :
Philip Mullineaux : mullin@essex.ac.uk
Host : jean-philippe.reichheld@univ-perp.fr