Strigolactone‐nitric oxide interplay in plants: The story has just begun

Abstract

Both strigolactones (SLs) and nitric oxide (NO) are regulatory signals with diverse roles during plant development and stress responses. This review aims to discuss the so far available data regarding SLs-NO interplay in plant systems. The majority of the few articles dealing with SL-NO interplay focuses on the root system and it seems that NO can be an upstream negative regulator of SL biosynthesis or an upstream positive regulator of SL signaling depending on the nutrient supply. From the so far published results it is clear that NO modifies the activity of target proteins involved in SL biosynthesis or signaling which may be a physiologically relevant interaction. Therefore, in silico analysis of NO-dependent posttranslational modifications in SL-related proteins was performed using computational prediction tools and putative NO-target proteins were specified. The picture is presumably more complicated, since also SL is able to modify NO levels. As a confirmation, author detected NO levels in different organs of max1-1 and max2-1 Arabidopsis and compared to the wild-type these mutants showed enhanced NO levels in their root tips indicating the negative effect of endogenous SLs on NO metabolism. Exogenous SL analogue-triggered NO production seems to contradict the results of the genetic study, which is an inconsistency should be taken into consideration in the future. In the coming years, the link between SL and NO signaling in further physiological processes should be examined and the possibilities of NO-dependent posttranslational modifications of SL biosynthetic and signaling proteins should be looked more closely.

Nitric oxide responses in Arabidopsis hypocotyls are mediated by diverse phytohormone pathways

“…These data point to NO as a potential key factor in SL-exerted opposite regulatory effects in root and shoot growth. As recently reviewed ( Kolbert 2018 ), the functional SL–NO interaction seems to be quite complex. It seems that NO positively regulates SL signaling but it does not influence either SL production or the expression of SL biosynthetic genes in rice roots ( Sun et al , 2016 ).…”

“…It seems that NO positively regulates SL signaling but it does not influence either SL production or the expression of SL biosynthetic genes in rice roots ( Sun et al , 2016 ). In contrast, the exogenous application of SLs induced the production of NO ( Kolbert, 2018 ; Lv et al , 2018 ), but it remains unclear whether NO actually induce the production of SLs. We found that the exogenous application of NO mildly activated the expression of MAX1 and even to a lesser extent MAX2 genes ( Fig.…”

Assessment of Subcellular ROS and NO Metabolism in Higher Plants: Multifunctional Signaling Molecules

“…Although the endogenous sources of enzymatic NO in higher plants remain a subject of debate such as it was mentioned previously, its presence and function in plant cells are clear [17]. NO performs a signaling function mainly through the PTMs, S-nitrosation, nitration, and metal nitrosylation, in order to regulate gene expression and its interaction with phytohormones [165].…”

“…The presence of NO in higher plants is well documented. However, how NO is enzymatically generated remains a matter of debate [16][17][18]. Up to now, two possible pathways have been recognized using as substrate either L-arginine (oxidative pathway) or nitrate/nitrite (reductive pathway) involving the contribution of a l-Arg-dependent NO synthase-like activity [19] and a nitrate reductase (NR) activity [20], respectively.…”

Strigolactones Interact With Nitric Oxide in Regulating Root System Architecture of Arabidopsis thaliana

“…Increasing (by the addition of GR24) or lowering (by the addition of TIS108) the optimal SL level may result in similarly inhibited growth processes. Treatment with GR24 resulted in significantly increased NO content in Arabidopsis roots (Kolbert, 2019). As for NOassociated genes, the expressions of NIA1 and NIA2 as well as GSNOR1 didn't show any relevant modification in the presence of GR24 ( Figure 6).…”