PIN-FORMED1 and PINOID regulate boundary formation and cotyledon development in Arabidopsis embryogenesis.
In dicotyledonous plants, two cotyledons are formed at bilaterally symmetric positions in the apical region of the embryo. Single mutations in the PIN-FORMED1 (PIN1) and PINOID (PID) genes, which mediate auxin-dependent organ formation, moderately disrupt the symmetric patterning of cotyledons. We report that the pin1 pid double mutant displays a striking phenotype that completely lacks cotyledons and bilateral symmetry. In the double mutant embryo, the expression domains of CUP-SHAPED COTYLEDON1 (CUC1), CUC2 and SHOOT MERISTEMLESS (STM), the functions of which are normally required to repress growth at cotyledon boundaries, expand to the periphery and overlap with a cotyledon-specific marker, FILAMENTOUS FLOWER. Elimination of CUC1, CUC2 or STM activity leads to recovery of cotyledon growth in the double mutant, suggesting that the negative regulation of these boundary genes by PIN1 and PID is sufficient for primordium growth. We also show that PID mRNA is localized mainly to the boundaries of cotyledon primordia and early expression of PID mRNA is dependent on PIN1. Our results demonstrate the redundant roles of PIN1 and PID in the establishment of bilateral symmetry, as well as in the promotion of cotyledon outgrowth, the latter of which involves the negative regulation of CUC1, CUC2 and STM genes, which are boundary-specific downstream effectors.
Furutani
Masahiko
M
Graduate School of Biological Sciences, Nara Institute of Science and Technology, Nara 630-0101, Japan.
Vernoux
Teva
T
Traas
Jan
J
Kato
Takehide
T
Tasaka
Masao
M
Aida
Mitsuhiro
M
D017360:Arabidopsis / Q000187:drug effects / Q000196:embryology* / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D018548:Cotyledon / Q000187:drug effects / Q000196:embryology* / Q000378:metabolism; D015536:Down-Regulation; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D007210:Indoleacetic Acids / Q000494:pharmacology; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism
D029681:Arabidopsis Proteins; C426007:CUC1 protein, Arabidopsis; C107294:CUC2 protein, Arabidopsis; D018398:Homeodomain Proteins; D007210:Indoleacetic Acids; D026901:Membrane Transport Proteins; C116363:PIN1 protein, Arabidopsis; C097496:STM protein, Arabidopsis; C405165:PINOID protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases