POTENTIAL FUNCTIONS OF ARABIDOPSIS THALIANA HEAT SHOCK PROTEINS IN THE PLANT APOPLAST

FRANCO ROSSI; SEBASTIÁN PÉREZ ROJAS; EDWIN SÁNCHEZ LÓPEZ; BIN DENG; FAN ZHANG; ANDRÉS GÁRRIZ; MARINA CLEMENTE; MARIANA CORIGLIANO

Salta

Congreso; LV Annual SAIB Meeting and XIV PABMB Congress; 2019

Hsp90s are found in all plant cellular compartments examined to date, including cytosol, nucleus, endoplasmic reticulum, mitochondria and chloroplasts. Besides, Hsp90s have also been found in the apoplast, even though their roles in this location remain elusive. Previously, we added some light to this issue by assessing the regulation of defense-associated mechanisms in Arabidopsis thaliana plants infiltrated with the recombinant Hsp90 protein rAtHsp81.2. In this trend, we showed that ROS production and callose deposition were incremented upon rAtHsp81.2 infiltration. Besides, a 24h pre-treatment of leaves with rAtHsp81.2 resulted in a reduction in the proliferation of Pseudomonas syringae pv. tomato DC3000, whereas the in vitro growth of the bacteria is not affected in the presence of rAtHsp81.2 suggesting that this protein may participate in the induction of defense. In the present study, we attempted to gain a deeper insight into the role played by apoplastic-localized Hsp90s by evaluating their effects on defense gene expression. We observed that rAtHsp81.2 infiltration downregulated the expression of PR1 and endogenous AtHsp81.2, while Pdf1.2 expression showed no statistical differences compared to mock-inoculated controls. However, pre-treatment of leaves with rAtHsp81.2 followed by infiltration with P. syringae provokes an opposite response to that in leaves infiltrated with AtHsp81.2 alone, as PR1 and AtHsp81.2 gene expression resulted up-regulated. Our results suggest that Hsp90s localized in the plant apoplast play an active role in the activation of the plant defense mechanisms against pathogens.