Two functionally distinct members of the MATE (multi-drug and toxic compound extrusion) family of transporters potentially underlie two major aluminum tolerance QTLs in maize
Article first published online: 10 DEC 2009
No claim to original US government works. Journal compilation © 2010 Blackwell Publishing Ltd
The Plant Journal
Volume 61, Issue 5, pages 728–740, March 2010
How to Cite
Maron, L. G., Piñeros, M. A., Guimarães, C. T., Magalhaes, J. V., Pleiman, J. K., Mao, C., Shaff, J., Belicuas, S. N.J. and Kochian, L. V. (2010), Two functionally distinct members of the MATE (multi-drug and toxic compound extrusion) family of transporters potentially underlie two major aluminum tolerance QTLs in maize. The Plant Journal, 61: 728–740. doi: 10.1111/j.1365-313X.2009.04103.x
- Issue published online: 22 FEB 2010
- Article first published online: 10 DEC 2009
- Received 20 August 2009; revised 11 November 2009; accepted 16 November 2009; published online 22 January 2010.
- multi-drug and toxic compound extrusion (MATE);
- organic acids
Crop yields are significantly reduced by aluminum (Al) toxicity on acidic soils, which comprise up to 50% of the world’s arable land. Al-activated release of ligands (such as organic acids) from the roots is a major Al tolerance mechanism in plants. In maize, Al-activated root citrate exudation plays an important role in tolerance. However, maize Al tolerance is a complex trait involving multiple genes and physiological mechanisms. Recently, transporters from the MATE family have been shown to mediate Al-activated citrate exudation in a number of plant species. Here we describe the cloning and characterization of two MATE family members in maize, ZmMATE1 and ZmMATE2, which co-localize to major Al tolerance QTL. Both genes encode plasma membrane proteins that mediate significant anion efflux when expressed in Xenopus oocytes. ZmMATE1 expression is mostly concentrated in root tissues, is up-regulated by Al and is significantly higher in Al-tolerant maize genotypes. In contrast, ZmMATE2 expression is not specifically localized to any particular tissue and does not respond to Al. [14C]-citrate efflux experiments in oocytes demonstrate that ZmMATE1 is a citrate transporter. In addition, ZmMATE1 expression confers a significant increase in Al tolerance in transgenic Arabidopsis. Our data suggests that ZmMATE1 is a functional homolog of the Al tolerance genes recently characterized in sorghum, barley and Arabidopsis, and is likely to underlie the largest maize Al tolerance QTL found on chromosome 6. However, ZmMATE2 most likely does not encode a citrate transporter, and could be involved in a novel Al tolerance mechanism.