A regulated auxin minimum is required for seed dispersal in Arabidopsis.
Local hormone maxima are essential for the development of multicellular structures and organs. For example, steroid hormones accumulate in specific cell types of the animal fetus to induce sexual differentiation and concentration peaks of the plant hormone auxin direct organ initiation and mediate tissue patterning. Here we provide an example of a regulated local hormone minimum required during organogenesis. Our results demonstrate that formation of a local auxin minimum is necessary for specification of the valve margin separation layer where Arabidopsis fruit opening takes place. Consequently, ectopic production of auxin, specifically in valve margin cells, leads to a complete loss of proper cell fate determination. The valve margin identity factor INDEHISCENT (IND) is responsible for forming the auxin minimum by coordinating auxin efflux in separation-layer cells. We propose that the simplicity of formation and maintenance make local hormone minima particularly well suited to specify a small number of cells such as the stripes at the valve margins.
Sorefan
Karim
K
Crop Genetics Department, John Innes Centre, Norwich Research Park, Colney Lane, Norwich, Norfolk NR4 7UH, UK.
Girin
Thomas
T
Liljegren
Sarah J
SJ
Ljung
Karin
K
Robles
Pedro
P
Galván-Ampudia
Carlos S
CS
Offringa
Remko
R
Friml
Jirí
J
Yanofsky
Martin F
MF
Østergaard
Lars
L
D017360:Arabidopsis / Q000033:anatomy & histology / Q000254:growth & development / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism; D001692:Biological Transport; D005638:Fruit / Q000033:anatomy & histology / Q000254:growth & development / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D007210:Indoleacetic Acids / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics; D012639:Seeds / Q000254:growth & development / Q000502:physiology*
D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D007210:Indoleacetic Acids; D026901:Membrane Transport Proteins; D017346:Protein Serine-Threonine Kinases; C484035:INDEHISCENT protein, Arabidopsis; C116363:PIN1 protein, Arabidopsis; C405165:PINOID protein, Arabidopsis; C542125:WAG2 protein, Arabidopsis