Hairy root exudates of allelopathic weed Chenopodium murale L. induce oxidative stress and down-regulate core cell cycle genes in Arabidopsis and wheat seedlings

Abstract

The effects of Chenopodium murale root exudates, applied as phytotoxic medias (PMs), were tested on Arabidopsis thaliana and Triticum aestivum. The effects of PMs, where wild-type roots (K), hairy roots derived from roots (R clones) or from cotyledons (C clones) were cultured, were different. K medium suppressed Arabidopsis germination, while other PMs reduced root and leaf elongation and the number of rosette leaves. R media were more phytotoxic than C media. Treatment of Arabidopsis with R8 downregulated expression of core cell cycle genes: cyclindependent kinase (CDK) A1;1, four B-class CDKs, and cyclins CYCA3;1, CYCB2;4, CYCD4;2 and CYCH1 in root and shoot tips. Only CYCD2;1 transcript was elevated in treated shoots, but down-regulated in roots. Wheat Ta-CDC2 and Ta-CYCD2 genes showed the same expression profiles as their Arabidopsis counterparts, CDKA1;1 and CYCD2;1. PMs also caused increase of antioxidative enzyme activities in both plants. Exposure of Arabidopsis to PMs induced one catalase isoform, but repressed another, resulting in no net change of catalase activity. Wheat seedlings treated with PMs had catalase activity significantly elevated in all treatments, particularly in shoots. In both plants, PMs induced the activity of different peroxidase isozymes and total peroxidase activity. Both plants responded to phytotoxic treatments by induction of CuZn-superoxide dismutase. Thus, the phytotoxicity of C. murale root exudates is, at least partially, based on down-regulation of the cell cycle regulators and on generation of oxidative stress in the affected plants. We propose that C. murale root exudates should be considered as means of biological weed control.

Physiological and cell ultrastructure disturbances in wheat seedlings generated by Chenopodium murale hairy root exudate

“…Rapid increase in H 2 O 2 level after R5 treatment (about 50% higher compared to control) represents the typical reaction to allelochemicals since the similar effect was annotated after application of numerous other allelochemicals (Soltys et al 2011(Soltys et al , 2014Guan et al 2014;Krasuska et al 2016;Andrzejczak et al 2018). Different increments of H 2 O 2 roots and shoots content could be explained by differential activation of enzymatic antioxidant defense system, observed in wheat shoot and root in the previous study (Dmitrović et al 2015a).…”

“…Despite induction of antioxidant enzymatic system, documented previously by Dmitrović et al (2015a), increased TBARS content, in both roots and shoots, suggested that generated ROS molecules could not be eliminated completely. This claim is supported by the results of H 2 O 2 content measurement and ROS imaging, using H 2 DCF-DA probe which also showed increased level of H 2 O 2 and other ROS molecules in tissues of R5 treated plants.…”

“…These visible growth-limiting effects of allelochemicals may be due to their effects on different levels of plant organization, such as reduction/inhibition of mitotic activity, ion uptake, photosynthesis, and enzyme action (Rice 1974). The previous study, related to possible inhibitory effects of Chenopodium murale root exudates on Arabidopsis and wheat plants grown in vitro (Dmitrović et al 2015a), revealed that the plant growth inhibition was, at least partially, based on downregulation of the cell cycle regulators and on generation of oxidative stress in the affected plants.…”

“…An in vitro liquid culture system of C. murale transgenic hairy roots has previously been established, as an alternative strategy for allelopathic assays (Mitić et al 2012), to facilitate research on C. murale allelopathic compounds. Bioassays revealed that C. murale hairy roots synthesize certain bioactive substances with inhibitory effect on seed germination and seedlings growth of crop plants, such as wheat and lettuce (Mitić et al 2012), collard greens (Mitić et al 2015), the model plant Arabidopsis thaliana (Dmitrović et al 2015a), and some weed species (Dmitrović et al 2015b).…”

“…The target plant response to allelopathic compounds may have different bases (Weir et al 2004). The previous study, where C. murale root exudates, applied as phytotoxic media (PMs) were tested on A. thaliana and wheat, revealed that the phytotoxicity of root exudates is, at least partially, based on downregulation of the cell cycle regulators and on the generation of oxidative stress in the affected plants (Dmitrović et al 2015a). However, besides enhanced activity of antioxidant enzymes and alterations in CDK (cyclin-dependent kinase) gene expression, inhibition generated by allelopathic compounds may also be the result of significant lipid peroxidation (Ding et al 2016;Hussain et al 2017), as well as the change of the content of the main phytohormones, e.g., abscisic acid, indole-3-acetic acid, and zeatin riboside (Yang et al 2008), modifications at cell ultrastructure level (Gniazdowska and Bogatek 2005;Kaur et al 2005;Romero-Romero et al 2005) and by biochemical and physiological processes (reviewed by Cheng and Cheng 2015).…”