Interplays between nitric oxide and reactive oxygen species in cryptogein signalling

Abstract

22The cellular messenger nitric oxide (NO) has many functions in plants. In this study, we 23 investigated its interplays with Reactive Oxygen Species (ROS) in the defense responses triggered by 24 the elicitin cryptogein produced by the oomycete Phytophthora cryptogea. The production of NO 25 induced by cryptogein in tobacco cell suspensions was partly regulated through a ROS--dependent 26 pathway involving the NADPH oxidase NtRBOHD. In turn, NO down--regulated the level of H 2 O 2 27 derived from NtRBOHD activity. Both NO and ROS synthesis appeared to be under the control of two 28 redundant isoforms of histone deacetylases of type 2 acting as negative regulators of cell death. 29Occurrence of an interplay between NO and ROS was further supported by the finding that 30 cryptogein triggered a fast production of peroxynitrite (ONOO ─ ) resulting from the coupling reaction 31 of superoxide (O 2•─ ) with NO. We provided evidence that ROS, but not NO, negatively regulate the 32 intensity of activity of the protein kinase NtOSAK, a member of the SnRK2 protein kinase family. 33Furthermore, using a micro--array approach, we next identified fifteen genes early induced by 34 cryptogein via NO. Interestingly, only a part of these genes was also modulated by ROS derived from 35NtRBOHD activity and encoded proteins showing sequence identity to ubiquitin ligases. Expression of 36 those genes appeared to be negatively regulated by ONOO ─ , suggesting that ONOO ─ mitigate the 37 effects of NO and ROS in cell response to cryptogein. Finally, we provided evidence that NO required 38NtRBOHD activity for inducing cell death, thus confirming previous assumption that ROS channel NO 39 through cell death pathways. 40 41

The effect of cryptogein with changed abilities to transfer sterols and altered charge distribution on extracellular alkalinization, ROS and NO generation, lipid peroxidation and LOX gene transcription in Nicotiana tabacum

“…It is well known that the productions of NO and ROS are higly crossregulated with one another. The generation of NO induced by cryptogein in tobacco cells was found to be partly under the control of a ROS-dependent pathway involving the NADPH oxidase (Kulik et al, 2015). Our results show that the low and delayed production of ROS did not affect the generation of NO, therefore, it seems that even this low ROS levels (0.23 mM 35 min after elicitation compared to about 5 mM in X24-treated leaves) represented sufficient signal needful for the NO synthesis.…”

“…Nevertheless, NO can react with superoxide anion as well leading to the generation of peroxynitrite (ONOO À ), a molecule causing nitration of protein tyrosine residues . This process was also recently described in cryptogein-treated tobacco plants by Kulik et al (2015). Therefore, the elimination of NO with superoxide anion strongly produced in X24, L15W/L36F and L19R-elicited cells could result in the detection of the increased NO level in L15W/ L36F þ R-treated cells.…”

“…As mentioned above, ROS, NO and LP are required for full development of HR-PCD in cryptogein-treated tobacco tissues, however, they are not the only factors leading to the HR cell death. Enzymes with caspase-like activities together with proteases, nucleases, ubiquitin-ligases, releasing of cytochrome c from mitochondria and, likely, microtubule depolymerization and others participate in the execution of PCD (Binet et al, 2001;Hatsugai et al, 2015;Kulik et al, 2015). In addition, previous data suggest that there are many variations of plant PCD in terms of which organelles play a central role in the initiation or execution of this process; PCD can be vacuolar, mitochondrial or chloroplast dependent (Rantong and Gunawardena, 2015).…”

“…ROS and NO act either independently or in a partnership in the regulation of expression of a broad spectrum of defence genes associated with the execution of HR cell death in plants (Zago et al, 2006). For instance, Kulik et al (2015) recently described that the concerted action of both NO and ROS regulates gene expression encoding putative ubiquitine ligases which however appeared to be negatively regulated by ONOO À . In addition, ROS and NO can directly inactivate proteins displaying chaperon-like activities.…”

Identification of nuclear target proteins for S-nitrosylation in pathogen-treated Arabidopsis thaliana cell cultures

“…S6), suggesting that nitric oxide is a new modulator of epigenetic processes in plants. In tobacco plant-specific type-2 histone deacetylases control cryptogein-induced NO and ROS production [71]. Moreover, these proteins negatively regulate elicitor-induced cell death suggesting that acetylation-dependent modifications of nuclear proteins are involved in HR control [72].…”