Wang Junjie, Hou Qiuqiang, Li Penghui, Yang Lina, Sun Xuecheng, Benedito Vagner A, Wen Jiangqi, Chen Beibei, Mysore Kirankumar S, Zhao Jian
National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, 430075, China.
Division of Plant & Soil Sciences, West Virginia University, Morgantown, WV, 26506, USA.
Plant J. 2017 Apr;90(1):79-95. doi: 10.1111/tpj.13471. Epub 2017 Feb 27.
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, Al 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 Al stress, and seedlings were chlorotic under Fe-deficient conditions. Overexpression of MtMATE66 rendered hairy roots more tolerant to Al 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 Al 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 Al stresses, but also casts light on their role in metal nutrition and hormone signaling under various stresses.
多药和毒素外排（MATE）转运蛋白家族在蒺藜苜蓿基因组中包含70个成员，它们发挥着看似重要但大多功能未知的生理功能。在此，我们运用生物信息学和分子遗传学方法来鉴定和表征参与柠檬酸输出、铝耐受性和铁转运的MATE转运蛋白。MtMATE69是一种受缺铁诱导的柠檬酸转运蛋白。在缺铁或铁供应过量条件下，MtMATE69在毛状根中的过表达改变了铁稳态和激素水平。MtMATE66是一种主要在根表皮细胞中表达的质膜柠檬酸转运蛋白。在铝胁迫下，mtmate66突变体的根生长比野生型少，并且在缺铁条件下幼苗黄化。MtMATE66的过表达使毛状根对铝毒性更具耐受性。MtMATE55参与幼苗发育、铁稳态以及激素信号传导。mtmate55突变体在成熟植株中发育延迟且叶片黄化。与野生型相比，MtMATE55的敲除突变体和过表达突变体均表现出铁积累改变和激素水平异常。我们证明锌指转录因子MtSTOP对于MtMATE66的表达以及植物对氢离子和铝毒性的抗性至关重要。两个先前已表征的MATE类黄酮转运蛋白MtMATE1和MtMATE2的正常表达也依赖于几种转录因子。这项研究不仅揭示了豆科植物中MATE转运蛋白的功能多样性以及抵御氢离子和铝胁迫的调控机制，还阐明了它们在各种胁迫下金属营养和激素信号传导中的作用。
