Coordination of apical and basal embryo development revealed by tissue-specific GNOM functions.
Flowering-plant embryogenesis generates the basic body organization, including the apical and basal stem cell niches, i.e. shoot and root meristems, the major tissue layers and the cotyledon(s). gnom mutant embryos fail to initiate the root meristem at the early-globular stage and the cotyledon primordia at the late globular/transition stage. Tissue-specific GNOM expression in the gnom mutant embryo revealed that both apical and basal embryo organization depend on GNOM provascular expression and a functioning apical-basal auxin flux: GNOM provascular expression in gnom mutant background resulted in non-cell-autonomous reconstitution of apical and basal tissues which could be linked to changes in auxin responses in those tissues, stressing the importance of apical-basal auxin flow for overall embryo organization. Although reconstitution of apical-basal auxin flux in gnom results in the formation of single cotyledons (monocots), only additional GNOM epidermal expression is able to induce wild-type apical patterning. We conclude that provascular expression of GNOM is vital for both apical and basal tissue organization, and that epidermal GNOM expression is required for radial-to-bilateral symmetry transition of the embryo. We propose GNOM-dependent auxin sinks as a means to generate auxin gradients across tissues.
ZMBP, Entwicklungsgenetik, Universität Tübingen, Auf der Morgenstelle 3, 72076 Tübingen, Germany.
Hanno
H
Wolters
Nadine
N
Anders
Niko
N
Geldner
Richard
R
Gavidia
Gerd
G
Jürgens
D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant / Q000235:genetics / Q000502:physiology; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D018519:Meristem / Q000235:genetics / Q000378:metabolism; D018613:Microscopy, Confocal; D008954:Models, Biological; D018517:Plant Roots / Q000196:embryology / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics
D029681:Arabidopsis Proteins; C088087:GNOM protein, Arabidopsis; D020662:Guanine Nucleotide Exchange Factors; D026901:Membrane Transport Proteins; C451260:PIN4 protein, Arabidopsis