Department of Plant Molecular Biology Younousse Saidi and Pierre Goloubinoff The plant heat-shock response is controlled by specific calcium channels in the plasma membrane
Dec 18, 2015
Department of Plant Molecular Biology
Younousse Saidi and Pierre Goloubinoff
The plant heat-shock response is controlled by specific calcium
channels in the plasma membrane
The heat-shock response
HSPs families: HSP100, HSP90, HSP70, HSP60, and small HSPs
Under normal conditions:
After temperature elevation:
The heat-shock response is a conserved reaction to elevated temperatures, featured by the synthesis of heat shock proteins (HSPs).
Contribute to the correct synthesis, subcellular targeting, or degradation of cellular proteins.
1- protect cells from severe damage (protein denaturation, membrane
hyperfluidity…), 2- allow resumption of normal cellular and physiological activities, 3- lead to a higher level of thermotolerance.
What is the principle sensing mechanism leading to the activation of heat-shock
genes?1- Cellular protein denaturation (Richard I. Morimoto, Genes & Dev. 1998)
2- The fluidity of the membrane
3- Evidences for the involvement of calcium ions and calmodulin in thermotolerance. (Gong et al. Plant Physiology 1998; Liu et al. Plant Cell Enviro 2006)
(Torok et al. PNAS. 2003)
Normal conditions
Heat shock
Investigation of the heat sensing mechanism using the moss Physcomitrella
patens
Size: µm - cm
Growth on liquid or solid medium
No multi-stratification, no vascular tissues and no cuticle
Growth as single cell-wide filaments (protonema)
Physcomitrella patens is optimal for stress studies because:
Highly amenable for genetic manipulations
We generated 3 different transgenic lines:
Ubi-1 Aequorinhsp17.3B GUS 35S Luciferase
Ca2+
Ca2+
Genome sequence available
Represents a important step in the evolution of land plants
Anti-GUS
(Saidi et al. 2005)
The stress-inducible promoter hsp17.3B is highly sensitive to small variation of
temperature
GUS expression after 1h heat shock
Immediatly after the HS
16h Recovery after the HS
Fv/Fm ratio: the maximal photochemical efficiency of PSII
hsp17.3B GUS
Environment Bio-monitoring:Screening for aromatic compounds that activate a
heat-shock stress response
(Saidi et al. 2007)
hsp17.3B GUS
5X
0X
Mild heat-treatment amplify chlorophenol effect and enhances bioassay sensitivity.
80X
4.5X
1
The synergistic effect between mild heat shock and TCP allows to detect lower concentrations of potential
toxic compounds
One hour exposure to different concentrations of trichlorophenol at 30 and 32°C
(Saidi et al. 2007)
Mild heat-treatment amplify chlorophenol effect and enhances bioassay sensitivity to lower TCP concentrations.
Mild heat treatment enhances bioassay sensitivity.
One hour exposure to 100 µM of different compounds at 30°C
The screen at 30°C allow to identify sulfonated anthraquinon as a co-activator of the heat shock response
1
One hour exposure to different concentrations of trichlorophenol at 25 or at 30°C
(Saidi et al. 2007)
hsp17.3B GUS
The heat-shock promoter is specifically activated by trichlorophenol (TCP) in a dose-
dependant manner.
0 1 2 4 20 2020 20TCP
DCPMCP
DMSO
time (h)
(Saidi et al. 2007)
Induction kinetics at 38°C
The nature of the heat shock signal is transienthsp17.3B GUS
The re-setting of the HSR is chaperone-independent
The full re-setting of the HSR requires about 5-7h at non-inducing temperature
Extracellular calcium ions are central to the heat-shock response
Chelating the extracellular calcium by EGTA inhibits the heat-shock response
hsp17.3B GUS
EGTA pre-treatment inhibits the heat-induced Ca2+ influx
Heat shock induces a transient elevation of cytosolic Ca2+ concentrations
Ubi-1 Aequorin
22 30 32 34 36 38 (°C)
GU
S a
cti
vity
The amplitude of temperature induced Ca2+ influx correlates with subsequent levels of GUS
(BA) Benzyl alcohol
(PCP) Pentachlorophenol
(Cel) Celastrol
Chemicals interacting with membranes induce Ca2+ influx that precede the activation of heat-shock
geneshsp17.3B GUS
(Saidi et al. 2005; Saidi et al. 2007)
Pierre Goloubinoff
Many thanks to
Maude Murise and Peter Coenig
Funding was from: