Maintenance of embryonic auxin distribution for apical-basal patterning by PIN-FORMED-dependent auxin transport in Arabidopsis.
Molecular mechanisms of pattern formation in the plant embryo are not well understood. Recent molecular and cellular studies, in conjunction with earlier microsurgical, physiological, and genetic work, are now starting to define the outlines of a model where gradients of the signaling molecule auxin play a central role in embryo patterning. It is relatively clear how these gradients are established and interpreted, but how they are maintained is still unresolved. Here, we have studied the contributions of auxin biosynthesis, conjugation, and transport pathways to the maintenance of embryonic auxin gradients. Auxin homeostasis in the embryo was manipulated by region-specific conditional expression of indoleacetic acid-tryptophan monooxygenase or indoleacetic acid-lysine synthetase, bacterial enzymes for auxin biosynthesis or conjugation. Neither manipulation of auxin biosynthesis nor of auxin conjugation interfered with auxin gradients and patterning in the embryo. This result suggests a compensatory mechanism for buffering auxin gradients in the embryo. Chemical and genetic inhibition revealed that auxin transport activity, in particular that of the PIN-FORMED1 (PIN1) and PIN4 proteins, is a major factor in the maintenance of these gradients.
Weijers
Dolf
D
Developmental Genetics, Institute of Biology, Leiden University, Clusius Laboratory, 2333 AL Leiden, The Netherlands.
Sauer
Michael
M
Meurette
Olivier
O
Friml
Jirí
J
Ljung
Karin
K
Sandberg
Göran
G
Hooykaas
Paul
P
Offringa
Remko
R
D017360:Arabidopsis / Q000033:anatomy & histology* / Q000196:embryology* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport / Q000502:physiology; D018506:Gene Expression Regulation, Plant; D017930:Genes, Reporter; D006706:Homeostasis; D007210:Indoleacetic Acids / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D009024:Morphogenesis; D030821:Plants, Genetically Modified; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism
D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; D026901:Membrane Transport Proteins; C116363:PIN1 protein, Arabidopsis; C451260:PIN4 protein, Arabidopsis; D011993:Recombinant Fusion Proteins