Scientific Reports (Jul 2017)

Evolutionarily conserved BIL4 suppresses the degradation of brassinosteroid receptor BRI1 and regulates cell elongation

  • Ayumi Yamagami,
  • Chieko Saito,
  • Miki Nakazawa,
  • Shozo Fujioka,
  • Tomohiro Uemura,
  • Minami Matsui,
  • Masaaki Sakuta,
  • Kazuo Shinozaki,
  • Hiroyuki Osada,
  • Akihiko Nakano,
  • Tadao Asami,
  • Takeshi Nakano

DOI
https://doi.org/10.1038/s41598-017-06016-2
Journal volume & issue
Vol. 7, no. 1
pp. 1 – 13

Abstract

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Abstract Brassinosteroids (BRs), plant steroid hormones, play important roles in plant cell elongation and differentiation. To investigate the mechanisms of BR signaling, we previously used the BR biosynthesis inhibitor Brz as a chemical biology tool and identified the Brz-insensitive-long hypocotyl4 mutant (bil4). Although the BIL4 gene encodes a seven-transmembrane-domain protein that is evolutionarily conserved in plants and animals, the molecular function of BIL4 in BR signaling has not been elucidated. Here, we demonstrate that BIL4 is expressed in early elongating cells and regulates cell elongation in Arabidopsis. BIL4 also activates BR signaling and interacts with the BR receptor brassinosteroid insensitive 1 (BRI1) in endosomes. BIL4 deficiency increases the localization of BRI1 in the vacuoles. Our results demonstrate that BIL4 regulates cell elongation and BR signaling via the regulation of BRI1 localization.