Chloroplast calcium signalling regulates thermomemory

Area of Science:

• Plant physiology
• Molecular biology
• Stress response

Background:

• Plants exhibit thermomemory, a cellular memory of heat stress, involving persistent heat shock proteins (HSPs).
• Resetting thermomemory is vital for growth, with autophagy recently implicated in this process.
• Heat stress elevates chloroplast calcium, partly mediated by the calcium sensing receptor (CAS) protein, but its role is unclear.

Purpose of the Study:

• To investigate the function of heat-induced chloroplast calcium signaling in thermomemory resetting.
• To compare thermomemory resetting mechanisms in wild-type (WT) and cas mutants with altered calcium signaling.

Main Methods:

• Comparative analysis of plant biomass and HSP degradation after thermopriming in WT and cas mutant Arabidopsis.
• Measurement of free amino acid levels as an indicator of autophagy.

Main Results:

• Cas mutants showed greater biomass and reduced degradation of HSP 17.6 after thermopriming compared to WT.
• Cas mutants did not exhibit increased free amino acid levels, suggesting impaired autophagy.
• Heat-induced chloroplast calcium elevation appears to positively regulate thermomemory resetting.

Conclusions:

• Heat-activated calcium signaling in chloroplasts plays a key role in resetting plant thermomemory.
• CAS protein-mediated calcium signaling influences HSP degradation and autophagy during thermomemory reset.
• Understanding this mechanism can inform strategies for improving plant resilience to heat stress.