Physiologia Plantarum 2014 © 2014 Scandinavian Plant Physiology Society, ISSN 0031-9317 Molecular characterization of the citrate transporter gene TaMATE1 and expression analysis of upstream genes involved in organic acid transport under Al stress in bread wheat (Triticum aestivum) Ana Luísa Garcia-Oliveira a,b,∗ , Paula Martins-Lopes a , Roser Tolrá c , Charlotte Poschenrieder c , Marta Tarquis b , Henrique Guedes-Pinto a and César Benito b,∗ a Centro de Genómica e Biotecnologia, Instituto de Biotecnologia e Bioengenharia (CGB/IBB), Universidade de Trás-os-Montes e Alto Douro (UTAD), PO Box 1013, 5001–801 Vila Real, Portugal b Departamento de Genética, Facultad de Biología, Universidad Complutense de Madrid (UCM), 28040 Madrid, Spain c Lab. Fisiología Vegetal, Facultad Biociencias, Universidad Autonoma de Barcelona, E-08193 Bellaterra, Spain Correspondence *Corresponding authors, e-mail: lishabaihe@hotmail.com; cebe8183@bio.ucm.es Received 12 August 2013; revised 27 January 2014 doi:10.1111/ppl.12179 In bread wheat, besides malate, the importance of citrate efflux for Al tolerance has also been reported. For better understanding the Al tolerance mechanism in bread wheat, here, we performed both a molecular characterization of the citrate transporter gene TaMATE1 and an investigation on the upstream vari- ations in citrate and malate transporter genes. TaMATE1 belong to multidrug transporter protein family, which are located on the long arm of homoeologous group 4 chromosomes (TaMATE1-4A, TaMATE1-4B TaMATE1-4D). TaMATE1 homoeologues transcript expression study exhibited the preponderance of homoeologue TaMATE1-4B followed by TaMATE1-4D whereas homoeologue TaMATE1-4A seemed to be silenced. TaMATE1, particularly homoeologue TaMATE1-4B and TaALMT1 transcripts were much more expressed in the root apices than in shoots of Al tolerant genotype Barbela 7/72/92 under both con- trol and Al stress conditions. In addition, in both tissues of Barbela 7/72/92, higher basal levels of these gene transcripts were observed than in Anahuac (Al sensitive). Noticeably, the presence of a transposon in the upstream of TaMATE1-4B in Barbela 7/72/92 seems to be responsible for its higher tran- script expression where it may confer citrate efflux. Thus, promoter variations (transposon in TaMATE1-4B upstream and type VI promoter in TaALMT1) asso- ciated with higher basal transcript expression of TaMATE1-4B and TaALMT1 clearly show how different mechanisms for Al tolerance operate simultane- ously in a single genotype. In conclusion, our results demonstrate that Barbela 7/72/92 has favorable alleles for these organic acids transporter genes which could be utilized through genomic assisted selection to develop improved cultivars for acidic soils. Abbreviations – 2D, two-dimensional; AACT, aluminum-activated citrate transporter; ALMT, Al-activated malate transporter; dNTP, deoxyribonucleotide triphosphates; EST, expressed sequence tag; MATE, multidrug and toxic compound exudation; OAs, organic acids; PCR, polymerase chain reaction; RT, reverse transcription; STOP, sensitive to proton rhizotoxicity. Physiol. Plant. 2014