Potential functions of Arabidopsis thaliana heat shock proteins in the plant apoplast

ROSSI, FRANCO R; PEREZ ROJAS, SEBASTIÁN; SÁNCHEZ LÓPEZ, EDWIN F; BIN, DENG; FAN, ZAHNG; GÁRRIZ, ANDRÉS; CLEMENTE, MARINA; CORIGLIANO, MARIANA G

Salta

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

Hsp90s are found in all plant cellular compartmentsexamined 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 addedsome light to this issue by assessing the regulation of defense-associated mechanismsin Arabidopsis thaliana plantsinfiltrated with the recombinant Hsp90 protein rAtHsp81.2. In this trend, weshowed that ROS production and callose deposition were incremented upon rAtHsp81.2infiltration. Besides, a 24h pre-treatment of leaves with rAtHsp81.2 resultedin a reduction in the proliferation of Pseudomonassyringae pv. tomato DC3000, whereas the invitro growth of the bacteria is not affected in the presence of rAtHsp81.2 suggestingthat this protein may participate in the induction of defense. In the presentstudy, we attempted to gain a deeper insight into the role played by apoplastic-localizedHsp90s by evaluating their effects on defense gene expression. We observed thatrAtHsp81.2 infiltration downregulated the expression of PR1 and endogenousAtHsp81.2, while Pdf1.2 expression showed no statistical differencescompared to mock-inoculated controls. However, pre-treatment of leaves withrAtHsp81.2 followed by infiltration with P.syringae provokes an opposite response to that in leaves infiltrated with AtHsp81.2alone, as PR1 and AtHsp81.2 gene expression resulted up-regulated.Our results suggest that Hsp90s localized in the plant apoplast play an activerole in the activation of the plant defense mechanisms against pathogens.