• HSFs
• heat shock
• Arabidopsis
• ANPs
• HSPs
• anoxia

Abstract- Abiotic stresses can strongly affect growth and development of plants. Although active research is going on in order to understand the mechanisms involved in plant stress-response, many questions about this issue have still to be answered in model plant system with the goal to transfer the knowledge to crop species.
Transcriptome studies of Arabidopsis thaliana under anaerobic condition (lack of oxygen) has allowed to suppose that genes coding for a particular and conservatively recognized group of proteins, -known as heat shock proteins (HSPs) and normally involved in the acquisition of thermotolerance under heat shock-, might play an important role also in survival to anaerobiosis.
Anoxia is charadcterized by a decrease in the energy and redox state of the cell, and last but not least, in the production of ROS (Reactive Oxygen Species). Here we investigated the possible role played by HSPs during anoxia response and their possible involvement during post anoxia recovery, likely resulting in oxidative stress.
Anoxia induces the expression of genes coding for Heat Shock Proteins (HSPs) in Arabidopsis, and sucrose plays a synergistic role in this process. Sucrose specifically acts as a signalling molecule that triggers the induction of HSPs under anoxia, but is unable to enhance the HSP expression induced by heat. Treatments inducing the expression of heat-shock proteins could enhance Arabidopsis tolerance to anoxia, suggesting that HSPs may play an important role in cells under anaerobic stress. A heat pretreatment can enhance anoxia tolerance in Arabidopsis seedlings, whereas an anoxia pretreatment does not confer tolerance to heat stress. Interestingly, the positive effect exerted by sucrose on the expression of HSPs correlates with enhanced anoxia tolerance. The effects of sucrose appear to be independent of the metabolic role of sucrose, since the inductive effects of sucrose are also observed in the alcohol dehydrogenase mutant (adh), which is unable to carry out the fermentative pathway under anoxia. Plants pretreated with moderately high illumination before anoxia express higher levels of HSPs and display a higher anoxia tolerance when compared to dark-adapted plants. Overall, the results indicate that treatments which pre-induce the expression of HSPs (heat, sucrose, light, hypoxia) also result in enhanced survival to anoxia
To deepen the possible role played by HSPs under anoxia, transcriptomic profilings have been analyzed and reveal a significant overlapping between anoxic and heat shock response.
In particular a Heat Shock Factor (HsfA2), involved in different abiotic stress responses in Arabidopsis, is likely a “master” upstream regulator of several heat-shock genes induced by anoxia.
In this respect, knock-out mutant for this Hsf results affected in the acquisition of anoxia-tolerance via heat-pretreatment , whereas 35S::HsfA2 overexpressing lines can better tolerate anoxia.
In this work, we conclude that a possible important involvement of HSPs is present also during plant response to anaerobiosis and we cannot exclude that these proteins might be required during post-anoxic recovery, when re-oxygenation can lead to the ROS formation.