TY - JOUR
T1 - Auxin requirements for a meristematic state in roots depend on a dual brassinosteroid function
AU - Ackerman-Lavert, M.
AU - Fridman, Y.
AU - Matosevich, R.
AU - Khandal, H.
AU - Friedlander-Shani, L.
AU - Vragović, K.
AU - Ben El, R.
AU - Horev, G.
AU - Tarkowská, D.
AU - Efroni, I.
AU - Savaldi-Goldstein, S.
N1 - Publisher Copyright:
Copyright © 2021 Elsevier Inc. All rights reserved.
PY - 2021/10/25
Y1 - 2021/10/25
N2 - Root meristem organization is maintained by an interplay between hormone signaling pathways that both interpret and determine their accumulation and distribution. The interacting hormones Brassinosteroids (BR) and auxin control the number of meristematic cells in the Arabidopsis root. BR was reported both to promote auxin signaling input and to repress auxin signaling output. Whether these contradicting molecular outcomes co-occur and what their significance in meristem function is remain unclear. Here, we established a dual effect of BR on auxin, with BR simultaneously promoting auxin biosynthesis and repressing auxin transcriptional output, which is essential for meristem maintenance. Blocking BR-induced auxin synthesis resulted in rapid BR-mediated meristem loss. Conversely, plants with reduced BR levels were resistant to a critical loss of auxin biosynthesis, maintaining their meristem morphology. In agreement, injured root meristems, which rely solely on local auxin synthesis, regenerated when both auxin and BR synthesis were inhibited. Use of BIN2 as a tool to selectively inhibit BR signaling yielded meristems with distinct phenotypes depending on the perturbed tissue: meristem reminiscent either of BR-deficient mutants or of high BR exposure. This enabled mapping of the BR-auxin interaction that maintains the meristem to the outer epidermis and lateral root cap tissues and demonstrated the essentiality of BR signaling in these tissues for meristem response to BR. BR activity in internal tissues however, proved necessary to control BR levels. Together, we demonstrate a basis for inter-tissue coordination and how a critical ratio between these hormones determines the meristematic state.
AB - Root meristem organization is maintained by an interplay between hormone signaling pathways that both interpret and determine their accumulation and distribution. The interacting hormones Brassinosteroids (BR) and auxin control the number of meristematic cells in the Arabidopsis root. BR was reported both to promote auxin signaling input and to repress auxin signaling output. Whether these contradicting molecular outcomes co-occur and what their significance in meristem function is remain unclear. Here, we established a dual effect of BR on auxin, with BR simultaneously promoting auxin biosynthesis and repressing auxin transcriptional output, which is essential for meristem maintenance. Blocking BR-induced auxin synthesis resulted in rapid BR-mediated meristem loss. Conversely, plants with reduced BR levels were resistant to a critical loss of auxin biosynthesis, maintaining their meristem morphology. In agreement, injured root meristems, which rely solely on local auxin synthesis, regenerated when both auxin and BR synthesis were inhibited. Use of BIN2 as a tool to selectively inhibit BR signaling yielded meristems with distinct phenotypes depending on the perturbed tissue: meristem reminiscent either of BR-deficient mutants or of high BR exposure. This enabled mapping of the BR-auxin interaction that maintains the meristem to the outer epidermis and lateral root cap tissues and demonstrated the essentiality of BR signaling in these tissues for meristem response to BR. BR activity in internal tissues however, proved necessary to control BR levels. Together, we demonstrate a basis for inter-tissue coordination and how a critical ratio between these hormones determines the meristematic state.
KW - auxin
KW - brassinosteroid
KW - differentiation
KW - hormone biosynthesis
KW - inter-tissue communication
KW - meristem maintenance
KW - regeneration
KW - root
UR - http://www.scopus.com/inward/record.url?scp=85118161304&partnerID=8YFLogxK
U2 - 10.1016/j.cub.2021.07.075
DO - 10.1016/j.cub.2021.07.075
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C2 - 34418341
AN - SCOPUS:85118161304
SN - 0960-9822
VL - 31
SP - 4462
EP - 4472
JO - Current Biology
JF - Current Biology
IS - 20
ER -