Functional roles of ALMT-type anion channels in malate-induced stomatal closure in tomato and Arabidopsis

Takayuki Sasaki, Michiyo Ariyoshi, Yoko Yamamoto, Izumi C. Mori

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


Guard-cell-type aluminium-activated malate transporters (ALMTs) are involved in stomatal closure by exporting anions from guard cells. However, their physiological and electrophysiological functions are yet to be explored. Here, we analysed the physiological and electrophysiological properties of the ALMT channels in Arabidopsis and tomato (Solanum lycopersicum). SlALMT11 was specifically expressed in tomato guard cells. External malate-induced stomatal closure was impaired in ALMT-suppressed lines of tomato and Arabidopsis, although abscisic acid did not influence the stomatal response in SlALMT11-knock-down tomato lines. Electrophysiological analyses in Xenopus oocytes showed that SlALMT11 and AtALMT12/QUAC1 exhibited characteristic bell-shaped current-voltage patterns dependent on extracellular malate, fumarate, and citrate. Both ALMTs could transport malate, fumarate, and succinate, but not citrate, suggesting that the guard-cell-type ALMTs are dicarboxylic anion channels activated by extracellular organic acids. The truncation of acidic amino acids, Asp or Glu, from the C-terminal end of SlALMT11 or AtALMT12/QUAC1 led to the disappearance of the bell-shaped current-voltage patterns. Our findings establish that malate-activated stomatal closure is mediated by guard-cell-type ALMT channels that require an acidic amino acid in the C-terminus as a candidate voltage sensor in both tomato and Arabidopsis.

Original languageEnglish
Pages (from-to)2337-2350
Number of pages14
JournalPlant Cell and Environment
Issue number8
Publication statusPublished - Aug 2022


  • ALMT channel
  • Arabidopsis
  • Solanum lycopersicum (tomato)
  • guard cells
  • malate
  • stomatal closure

ASJC Scopus subject areas

  • Physiology
  • Plant Science


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