Targeting redox metabolism of the maize‐ Azospirillum brasilense interaction exposed to arsenic‐affected groundwater

PERALTA, JUAN MANUEL; BIANUCCI, ELIANA; ROMERO?PUERTAS, MARÍA C.; FURLAN, ANA; CASTRO, STELLA; TRAVAGLIA, CLAUDIA

PHYSIOLOGIA PLANTARUM

WILEY-BLACKWELL PUBLISHING, INC

Año: 2021

0031-9317

Arsenic in groundwater constitutes an agronomic problem since its closeness to the rhizosphere allows plant roots to absorb it affecting vital cellular processes and increasing possible accumulation into edible parts. Among the available agro-sustainable tools to reduce metal(oid)s toxicity, the use of Plant Growth-Promoting Bacteria (PGPB) becomes important. For that, and based on previous results in which significant differences of As translocation were observed when inoculating Az39 or CD Azospirillum strains on maize plants, in this manuscript we decided to decipher the redox metabolism changes and the antioxidant system response of maize plants inoculated with each strain, when exposed to a realistic arsenate (AsV) dose. Results showed that AsV caused morphological changes in root exodermis. Photosynthetic pigments decreased only in CD inoculated plants, while oxidative stress evidence was detected throughout the plant, regardless of the assayed strain. The antioxidant response was strain-differential since only CD inoculated plants showed an increase in superoxide dismutase, glutathione S-transferase (GST) and glutathione reductase (GR) activities while other enzymes showed the same behaviour irrespective of the inoculated strain. Regarding the analysis of the relative expression of the antioxidant enzymes, only the GST23 transcript level was upregulated by arsenate, regardless of the inoculated strain. AsV diminished the glutathione (GSH) content of roots inoculated with Az39 strain, and CD inoculated plants showed a decrease of oxidized GSH (GSSG) level. We suggest a model in which the antioxidant response of the maize-diazotrophs system is modulated by the strain and that GSH plays a central role acting mainly as a substrate for GST. These findings generate knowledge for a suitable PGPB selection, and its scaling to an effective bioinoculant formulation for maize crops exposed to adverse environmental conditions.