MONOPTEROS controls embryonic root initiation by regulating a mobile transcription factor.
Acquisition of cell identity in plants relies strongly on positional information, hence cell-cell communication and inductive signalling are instrumental for developmental patterning. During Arabidopsis embryogenesis, an extra-embryonic cell is specified to become the founder cell of the primary root meristem, hypophysis, in response to signals from adjacent embryonic cells. The auxin-dependent transcription factor MONOPTEROS (MP) drives hypophysis specification by promoting transport of the hormone auxin from the embryo to the hypophysis precursor. However, auxin accumulation is not sufficient for hypophysis specification, indicating that additional MP-dependent signals are required. Here we describe the microarray-based isolation of MP target genes that mediate signalling from embryo to hypophysis. Of three direct transcriptional target genes, TARGET OF MP 5 (TMO5) and TMO7 encode basic helix-loop-helix (bHLH) transcription factors that are expressed in the hypophysis-adjacent embryo cells, and are required and partially sufficient for MP-dependent root initiation. Importantly, the small TMO7 transcription factor moves from its site of synthesis in the embryo to the hypophysis precursor, thus representing a novel MP-dependent intercellular signal in embryonic root specification.
Schlereth
Alexandra
A
Entwicklungsgenetik, Zentrum für Molekularbiologie der Pflanzen (ZMBP), Universität Tübingen, Auf der Morgenstelle 3, 72076 Tübingen, Germany.
Möller
Barbara
B
Liu
Weilin
W
Kientz
Marika
M
Flipse
Jacky
J
Rademacher
Eike H
EH
Schmid
Markus
M
Jürgens
Gerd
G
Weijers
Dolf
D
D017360:Arabidopsis / Q000166:cytology / Q000196:embryology* / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D047108:Embryonic Development / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics; D007210:Indoleacetic Acids / Q000378:metabolism; D018519:Meristem / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D018517:Plant Roots / Q000166:cytology / Q000196:embryology* / Q000378:metabolism*; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism*
D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins; D007210:Indoleacetic Acids; D014157:Transcription Factors; C111371:MONOPTEROS protein, Arabidopsis; C549371:TARGET OF MP 5 protein, Arabidopsis; C549372:TMO7 protein, Arabidopsis