Genetically Modified Heat Shock Protein90s and Polyamine Oxidases in Arabidopsis Reveal Their Interaction under Heat Stress Affecting Polyamine Acetylation, Oxidation and Homeostasis of Reactive Oxygen Species

Abstract

The chaperones, heat shock proteins (HSPs), stabilize proteins to minimize proteotoxic stress, especially during heat stress (HS) and polyamine (PA) oxidases (PAOs) participate in the modulation of the cellular homeostasis of PAs and reactive oxygen species (ROS). An interesting interaction of HSP90s and PAOs was revealed in Arabidopsis thaliana by using the pLFY:HSP90RNAi line against the four AtHSP90 genes encoding cytosolic proteins, the T-DNA Athsp90-1 and Athsp90-4 insertional mutants, the Atpao3 mutant and pharmacological inhibitors of HSP90s and PAOs. Silencing of all cytosolic HSP90 genes resulted in several-fold higher levels of soluble spermidine (S-Spd), acetylated Spd (N8-acetyl-Spd) and acetylated spermine (N1-acetyl-Spm) in the transgenic Arabidopsis thaliana leaves. Heat shock induced increase of soluble-PAs (S-PAs) and soluble hydrolyzed-PAs (SH-PAs), especially of SH-Spm, and more importantly of acetylated Spd and Spm. The silencing of HSP90 genes or pharmacological inhibition of the HSP90 proteins by the specific inhibitor radicicol, under HS stimulatory conditions, resulted in a further increase of PA titers, N8-acetyl-Spd and N1-acetyl-Spm, and also stimulated the expression of PAO genes. The increased PA titers and PAO enzymatic activity resulted in a profound increase of PAO-derived hydrogen peroxide (H2O2) levels, which was terminated by the addition of the PAO-specific inhibitor guazatine. Interestingly, the loss-of-function Atpao3 mutant exhibited increased mRNA levels of selected AtHSP90 genes. Taken together, the results herein reveal a novel function of HSP90 and suggest that HSP90s and PAOs cross-talk to orchestrate PA acetylation, oxidation, and PA/H2O2 homeostasis.

An Undefined Interaction between Polyamines and Heat Shock Proteins Leads to Cellular Protection in Plasmodium falciparum and Proliferating Cells in Various Organisms

“…A more detailed, molecular analysis for the interaction between PAs and Hsps has been performed in Arabidopsis thaliana [ 37 ]. Exogenous Spm increased the transcription of Hsp90 and subsequently enhanced heat tolerance.…”

“…Interestingly, silencing of the four cytosolic Hsp90 genes resulted in a significant shift of the metabolic status of polyamines. Several-fold higher levels of soluble spermidine (S-Spd), acetylated Spd (N 8 -acetyl-Spd) and acetylated spermine (N 1 -acetyl-Spm) were detected in the silenced transgenic Arabidopsis thaliana lines [ 37 ]. A loss-of-function mutant in one of the Hsps encoding genes led to an increase of polyamine oxidase activity (PAO) with a significant release of hydrogen peroxide (H 2 O 2 ).…”

Update on the Roles of Polyamines in Fleshy Fruit Ripening, Senescence, and Quality

“…Remarkable progress has recently been made linking PAs and other signaling molecules such as H 2 O 2 , NO, and Ca 2+ in plants ( Niu and Liao, 2016 ; Guo et al, 2018 ; Toumi et al, 2019 ; Wang et al, 2019 ; Mo et al, 2020 ). Reactive oxygen species (ROS) produced by the action of the PAO enzyme may serve as secondary messengers, whereby the upregulation of CuAO/PAO expression further raises ROS levels, resulting in the acceleration of fruit ripening ( Wang et al, 2019 ).…”

CsPAO2 Improves Salt Tolerance of Cucumber through the Interaction with CsPSA3 by Affecting Photosynthesis and Polyamine Conversion

“…NADPH oxidase and PAO formed a feedback loop to regulate ROS homeostasis in tobacco, which affected stress tolerance [ 17 ]. Toumi et al [ 18 ] found that under heat stress, silencing HSP90 genes resulted in an elevated level of polyamine and acetylated polyamine, leading to enhanced AtPAOs expression, and proposed that HSP90s and PAO cross-talked to influence polyamine acetylation, oxidation and ROS homeostasis. To date, there have been few reports about the interacting proteins of PAO in plants.…”