TY - JOUR
T1 - Localization and speciation of arsenic in Glomus intraradices by synchrotron radiation spectroscopic analysis
AU - González-Chávez, Ma del Carmen A.
AU - Miller, Bradley
AU - Maldonado-Mendoza, Ignacio Eduardo
AU - Scheckel, Kirk
AU - Carrillo-González, Rogelio
N1 - Funding Information:
We thank M.Sc. Juan Carlos Martínez-Álvarez for his technical assistance in the preparation of mycorrhizal monoxenic fungal cultures. Critical review from Dr. Richard Loeppert is recognized. This project was partially supported by the Collaborative Research Grant Program Texas A&M-CONACyT ( 2009-021 ). This work was performed at the XSD/PNC Sector 20 beamline of the Advanced Photon Source (APS) of Argonne National Laboratory (Argonne, IL) through the contract no. DE_AC02-06CH11357.
PY - 2014
Y1 - 2014
N2 - The protective mechanisms employed by arbuscular mycorrhizal fungi (AMF) to reduce the toxic effects of arsenic on host plants remain partially unknown. The goal of this research was identifying the in situ localization and speciation of arsenic (As) in the AM fungus Rhizophagus intraradices [formerly named Glomus intraradices] exposed to arsenate [As(V)]. By using a two-compartment invitro fungal cultures of R. intraradices-transformed carrot roots, microspectroscopic X-ray fluorescence (μ-XRF), and microspectroscopic X-ray absorption near edge structure (μ-XANES), we observed that As(V) is absorbed after 1h in the hyphae of AMF. Three hours after exposure a decrease in the concentration of As was noticed and after 24 and 72h no detectable As concentrations were perceived suggesting that As taken up was pumped out from the hyphae. No As was detected within the roots or hyphae in the root compartment zone three or 45h after exposure. This suggests a dual protective mechanism to the plant by rapidly excluding As from the fungus and preventing As translocation to the plant root. μ-XANES data showed that gradual As(V) reduction occurred in the AM hyphae between 1 and 3h after arsenic exposure and was completed after 6h. Principal component analysis (PCA) and linear combination fitting (LCF) of μ-XANES data showed that the dominant species after reduction of As(V) by R. intraradices extra-radical hyphal was As(III) complexed with a reduced iron(II) carbonate compound. The second most abundant As species present was As(V)-iron hydroxides. The remaining As(III) compounds identified by the LCF analyses suggested these molecules were made of reduced As and S. These results increase our knowledge on the mechanism of As transport in AMF and validate our hypotheses that R. intraradices directly participates in arsenic detoxification. These fungal mechanisms may help AMF colonized plants to increase their tolerance to As at contaminated sites.
AB - The protective mechanisms employed by arbuscular mycorrhizal fungi (AMF) to reduce the toxic effects of arsenic on host plants remain partially unknown. The goal of this research was identifying the in situ localization and speciation of arsenic (As) in the AM fungus Rhizophagus intraradices [formerly named Glomus intraradices] exposed to arsenate [As(V)]. By using a two-compartment invitro fungal cultures of R. intraradices-transformed carrot roots, microspectroscopic X-ray fluorescence (μ-XRF), and microspectroscopic X-ray absorption near edge structure (μ-XANES), we observed that As(V) is absorbed after 1h in the hyphae of AMF. Three hours after exposure a decrease in the concentration of As was noticed and after 24 and 72h no detectable As concentrations were perceived suggesting that As taken up was pumped out from the hyphae. No As was detected within the roots or hyphae in the root compartment zone three or 45h after exposure. This suggests a dual protective mechanism to the plant by rapidly excluding As from the fungus and preventing As translocation to the plant root. μ-XANES data showed that gradual As(V) reduction occurred in the AM hyphae between 1 and 3h after arsenic exposure and was completed after 6h. Principal component analysis (PCA) and linear combination fitting (LCF) of μ-XANES data showed that the dominant species after reduction of As(V) by R. intraradices extra-radical hyphal was As(III) complexed with a reduced iron(II) carbonate compound. The second most abundant As species present was As(V)-iron hydroxides. The remaining As(III) compounds identified by the LCF analyses suggested these molecules were made of reduced As and S. These results increase our knowledge on the mechanism of As transport in AMF and validate our hypotheses that R. intraradices directly participates in arsenic detoxification. These fungal mechanisms may help AMF colonized plants to increase their tolerance to As at contaminated sites.
KW - Arbuscular mycorrhizal fungi
KW - Arsenate
KW - Arsenite
KW - Reduction
KW - X-ray absorption near edge spectroscopy
UR - http://www.scopus.com/inward/record.url?scp=84901463107&partnerID=8YFLogxK
U2 - 10.1016/j.funbio.2014.03.002
DO - 10.1016/j.funbio.2014.03.002
M3 - Artículo
SN - 1878-6146
VL - 118
SP - 444
EP - 452
JO - Fungal Biology
JF - Fungal Biology
IS - 5-6
ER -