title: Diverse functions of multidrug and toxin extrusion (MATE) transporters in citric acid efflux and metal homeostasis in Medicago truncatula.
abstract: The multidrug and toxin extrusion (MATE) transporter family comprises 70 members in the Medicago truncatula genome, and they play seemingly important, yet mostly uncharacterized, physiological functions. Here, we employed bioinformatics and molecular genetics to identify and characterize MATE transporters involved in citric acid export, Al3+tolerance and Fe translocation. MtMATE69 is a citric acid transporter induced by Fe-deficiency. Overexpression of MtMATE69 in hairy roots altered Fe homeostasis and hormone levels under Fe-deficient or Fe-oversupplied conditions. MtMATE66 is a plasma membrane citric acid transporter primarily expressed in root epidermal cells. The mtmate66 mutant had less root growth than the wild type under Al3+stress, and seedlings were chlorotic under Fe-deficient conditions. Overexpression of MtMATE66 rendered hairy roots more tolerant to Al3+toxicity. MtMATE55 is involved in seedling development and iron homeostasis, as well as hormone signaling. The mtmate55 mutant had delayed development and chlorotic leaves in mature plants. Both knock-out and overexpression mutants of MtMATE55 showed altered Fe accumulation and abnormal hormone levels compared with the wild type. We demonstrate that the zinc-finger transcription factor MtSTOP is essentially required for MtMATE66 expression and plant resistance to H+and Al3+toxicity. The proper expression of two previously characterized MATE flavonoid transporters MtMATE1 and MtMATE2 also depends on several transcription factors. This study reveals not only functional diversity of MATE transporters and regulatory mechanisms in legumes against H+and Al3+stresses, but also casts light on their role in metal nutrition and hormone signaling under various stresses.
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, 430075, China.
authors.forename: Junjie
authors.initials: J
authors.lastname: Wang
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, 430075, China.
authors.forename: Qiuqiang
authors.initials: Q
authors.lastname: Hou
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, 430075, China.
authors.forename: Penghui
authors.initials: P
authors.lastname: Li
authors.affiliation: Division of Plant & Soil Sciences, West Virginia University, Morgantown, WV, 26506, USA.
authors.forename: Lina
authors.initials: L
authors.lastname: Yang
authors.affiliation: College of Resources & Environment, Huazhong Agricultural University, Wuhan, 430075, China.
authors.forename: Xuecheng
authors.initials: X
authors.lastname: Sun
authors.affiliation: Division of Plant & Soil Sciences, West Virginia University, Morgantown, WV, 26506, USA.
authors.forename: Vagner A
authors.identifier: http://orcid.org/0000-0002-2131-7651
authors.initials: VA
authors.lastname: Benedito
authors.affiliation: Plant Biology Division, the Samuel Roberts Noble Foundation, Ardmore, OK, 73401, USA.
authors.forename: Jiangqi
authors.initials: J
authors.lastname: Wen
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, 430075, China.
authors.forename: Beibei
authors.initials: B
authors.lastname: Chen
authors.affiliation: Plant Biology Division, the Samuel Roberts Noble Foundation, Ardmore, OK, 73401, USA.
authors.forename: Kirankumar S
authors.initials: KS
authors.lastname: Mysore
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, 430075, China.
authors.forename: Jian
authors.identifier: http://orcid.org/0000-0002-4416-7334
authors.initials: J
authors.lastname: Zhao
mesh_terms: D000535:Aluminum / Q000378:metabolism; D001692:Biological Transport / Q000235:genetics / Q000502:physiology; D019343:Citric Acid / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant / Q000235:genetics / Q000502:physiology; D006706:Homeostasis / Q000235:genetics / Q000502:physiology; D007501:Iron / Q000378:metabolism; D046913:Medicago truncatula / Q000235:genetics / Q000378:metabolism*; D027701:Organic Cation Transport Proteins / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism
chemical_list: D027701:Organic Cation Transport Proteins; D010940:Plant Proteins; D019343:Citric Acid; D000535:Aluminum; D007501:Iron
keywords: Fe translocation; H+ and Al3+ toxicity; MATE transporter; citrate efflux; transcriptional regulation; zinc finger