On the mechanisms of cadmium stress alleviation in Medicago truncatula by arbuscular mycorrhizal symbiosis: A root proteomic study

Abstract

The arbuscular mycorrhizal (AM) symbiosis belongs to the strategies plants have developed to cope with adverse environmental conditions including contamination by heavy metals such as cadmium (Cd). In the present work, we report on the protective effect conferred by AM symbiosis to the model legume Medicago truncatula grown in presence of Cd, and on the 2-D-based proteomic approach further used to compare the proteomes of M. truncatula roots either colonised or not with the AM fungus Glomus intraradices in Cd-free and Cd-contaminated substrates. The results indicated that at the proteome level, 9 out of the 15 cadmium-induced changes in nonmycorrhizal roots were absent or inverse in those Cd-treated and colonized by G. intraradices, including the G. intraradices-dependent down-accumulation of Cd stress-responsive proteins. Out of the twenty-six mycorrhiza-related proteins that were identified, only six displayed changes in abundance upon Cd exposure, suggesting that part of the symbiotic program, which displays low sensitivity to Cd, may be recruited to counteract Cd toxicity through the mycorrhiza-dependent synthesis of proteins having functions putatively involved in alleviating oxidative damages, including a cyclophilin, a guanine nucleotide-binding protein, an ubiquitin carboxyl-terminal hydrolase, a thiazole biosynthetic enzyme, an annexin, a glutathione S-transferase (GST)-like protein, and a S-adenosylmethionine (SAM) synthase.

Effect of mycorrhizal inoculations on heavy metal uptake and stress alleviation of Cajanus cajan (L.) Millsp. genotypes grown in cadmium and lead contaminated soils

“…All the antioxidant (SOD, CAT, POX, and GR) activities in case of mycorrhizal plants were significantly higher than those of non-mycorrhizal plants at all concentrations, suggesting that AM fungal inoculation could improve the antioxidant enzyme systems to alleviate destructive stress. A positive role of AM in defence mechanisms under individual metal treatments has been reported (Bowler et al 1992;Rivera-Becerril et al 2005;Aloui et al 2009). …”

Modulation of Exogenous Glutathione in Ultrastructure and Photosynthetic Performance Against Cd Stress in the Two Barley Genotypes Differing in Cd Tolerance

“…Soil Cd contamination remains a concern because of Cd long half-life and easy uptake by plants and being a potential threat on human health [17,18]. Researchers have examined that the addition of synthetic chelators could improve phytoremediation efficiency [19].…”

Proteomic studies of arbuscular mycorrhizal associations

“…These observations indicate that AM colonization in M. truncatula alleviates the stress caused by cadmium and that this effect can be detected by variations in protein expression levels. Analysis by Reverse Trancriptase PCR (RT-PCR) indicated direct correlation between transcript amounts of two genes and the accumulation of the correspondent proteins, which indicates that this regulation may happen at the transcription level [54]. Later, tandem mass spectrometry sequencing of proteins induced by inoculation of M. truncatula by either G. mosseae or G. intraradices allowed for the identification of eleven proteins of fungal origin into the root system, the first insight into fungal proteins involved in AM colonization [55].…”