Submitted to: American Society of Plant Biologists Annual Meeting
Publication Type: Abstract only
Publication Acceptance Date: 3/19/2004
Publication Date: 7/24/2004
Citation: Pineros, M., Mason, P.A., Kochian, L.V. 2004. Understanding the role of membrane transport in the physiology of aluminum toxicity and tolerance. American Society of Plant Biologists Annual Meeting. p. 325. Interpretive Summary:
Technical Abstract: The presence of Al in the rhizosphere triggers diverse Al-induced toxic responses (primarily inhibition of root growth), as well as Al-tolerance responses (exudation of Al-chelating organic acids) at the root apex. We have made significant progress using the patch clamp technique to investigate the effect of Al on the endogenous plasma membrane (PM) transporters involved in both Al toxicity and Al-tolerance responses. These findings indicate that Al inhibits K+ transporters as well as H+-ATPase activity. However, in addition, Al also activates a plasma membrane anion channel, which is likely the primary transporter facilitating the organic acid exudation tolerance response. In order to isolate and characterize these diverse and contrasting responses to Al, we are currently essaying Al effects on different plasma membrane transporters expressed in heterologous systems. We have generated GFP constructs of several anion (CLC anion channel family) and one K+ transporter, and have expressed these chimeras under the control of the CMV-35S promoter in both Xenopus oocytes and mammalian (HEK 293) cells. Transient HEK 293 cell transfections indicate these chimeras are mainly localized to the PM. We are currently generating stable HEK 293 lines to assay the functional expression and biophysical transport properties of these channels by two electrode voltage-clamp and patch clamp approaches. Given that our previous results have indicated that the mechanism required for Al-activation of anion channel is solely localized to the PM, it will be of special interest to determine if any of the ClC channels can be directly activated by Al, or the Al- signaling cascade involves other type of Al receptors localized to the PM (Supported by USDA-NRI Grant 00-35100-9280).