The reduction of Cr(VI) in Salvinia minima. Possible involvement of an h-type thioredoxin

CHOCOBAR PONCE SILVANA; PRADO CAROLINA DEL VALLE; TABERNERO ROMINA; ILINA NATALIA; PAGANO ANTONIO EDUARDO; RAMALLO LOPEZ JOSE MARIA; MIZRAHI MARTÍN; ROSA MARIANA DANIELA

Buenos Aires

Congreso; XXXIII Argentinian meeting of plants physiologyc; 2021

Sociedad Argentina de Fisiología Vegetal

Cr(VI) is extremely toxic to plant cells and has been recognized to possess a high redox potential. Tolerant plant species have shown the ability to reduce Cr(VI) but the operating mechanism involved in this process are not elucidated. The aim of this study was to investigate the possible involvement of thiolic and phenolic compounds, and thioredoxin expression during Cr(VI) reduction in S. minima. In addition, a probable enzymatic reduction of Cr(VI) was investigated. Plants were exposed to 20 mg L-1 Cr(VI) during 7 days under controlled conditions. The amount of metal accumulated in lacinias and fronds indicated that a low percentage of absorbed Cr(VI) was mobilized from lacinias to fronds. X-ray absorption near-edge structure (XANES) analysis revealed that Cr(III) was the only chromium species occurring in S. minima plants. The expression of an h-type thioredoxin was demonstrated for the first time in Cr-exposed lacinias. Thiols and phenolics of lacinias and fronds were increased significantly by Cr(VI) treatment, but accumulation patterns were different indicating probably different roles in Cr(VI) detoxification. We suggest that operating mechanisms would be related to the amount of Cr absorbed and the organ considered. Thus, in lacinias, where higher Cr accumulation occurs, the most predominant mechanisms could be the metal complexation with insoluble phenolics and thiols bound protein, with a lower participation of soluble compounds (e.g. soluble phenolics, non-protein thiols). While in fronds, with low Cr accumulation, the reduction mechanism would be more related to soluble phenolics, non-protein thiols, and an unknown enzyme able to reduce Cr(VI).