Unraveling the effect of arsenic on the model Medicago–Ensifer interaction: a transcriptomic meta‐analysis

Abstract

SummaryThe genetic regulation underlying the effect of arsenic (As(III)) on the model symbiosis Medicago-Ensifer was investigated using a combination of physiological (split-roots), microscopy and genetic (microarrays, qRT-PCR and composite plants) tools.Nodulation was very sensitive to As(III) (median inhibitory dose (ID50) = 20 lM). The effect on root elongation and on nodulation was local (nonsystemic). A battery of stress (salt, drought, heat shock, metals, etc.)-related genes were induced. Glutathione played a pivotal role in tolerance/detoxification, together with secondary metabolites ((iso)flavonoids and phenylpropanoids). However, antioxidant enzymes were not activated.Concerning the symbiotic interaction, molecular evidence suggesting that rhizobia alleviate As stress is for the first time provided. Chalcone synthase (which is involved in the first step of the legume-rhizobia cross-talk) was strongly enhanced, suggesting that the plants are biased to establish symbiotic interactions under As(III) stress. In contrast, 13 subsequent nodulation genes (involved in nodulation factors (Nod factors) perception, infection, thread initiation and progression, and nodule morphogenesis) were repressed.Overexpression of the ethylene responsive factor ERN in composite plants reduced root stress and partially restored nodulation, whereas overexpression of the early nodulin ENOD12 enhanced nodulation both in the presence and, particularly, in the absence of As, without affecting root elongation. Several transcription factors were identified, which could be additional targets for genetic engineering aiming to improve nodulation and/or alleviate root stress induced by this toxic.

Use of Endophytic and Rhizosphere Bacteria To Improve Phytoremediation of Arsenic-Contaminated Industrial Soils by Autochthonous Betula celtiberica

“…Interestingly, previous studies indicated that these strains exhibit traits of interest for phytoextraction. Thus, species of the Ensifer genus were found in association with Medicago plants, where inoculated plants exhibited a reduction in the stress response, thereby indicating the protective effect of As-tolerant rhizobia (41). It has been demonstrated that Rhizobium species promoted plant growth in Lolium multiflorum (Lam.)…”

Linking Genes to Microbial Biogeochemical Cycling: Lessons from Arsenic

“…Sinorbizobium ) medicae MA11. 174 This study identified the adaptive responses of the bacterial symbiont to arsenic exposure. This metatranscriptomic approach will be useful to study how microbes regulate their genes to adapt to the changes in environmental conditions, particularly arsenic concentrations.…”

Transcriptomic Analysis Reveals Adaptive Responses of an Enterobacteriaceae Strain LSJC7 to Arsenic Exposure

“…For example, a microarray analysis shows that approximately 14% of the whole Herminiimonas asoxydans genome is significantly affected by 15 min of As(III) exposure ( Cleiss-Arnold et al, 2010 ). Though numerous studies have explored the profiling analysis of the whole organism’s metabolic pathways in response to As stress in plants and animals ( Zheng et al, 2005 ; Yu et al, 2012 ; Lafuente et al, 2014 ); the biochemical and molecular mechanisms of As-induced cytotoxicity in bacteria and bacterial responses to that cytotoxicity remain largely unknown. However, understanding the As resistance of bacteria is crucial because of the increasing As contamination in the environment.…”