MACCHI-BOU 2 is required for early embryo patterning and cotyledon organogenesis in Arabidopsis.
The phytohormone auxin is a key regulator of organogenesis in plants and is distributed asymmetrically via polar transport. However, the precise mechanisms underlying auxin-mediated organogenesis remain elusive. Here, we have analyzed the macchi-bou 2 (mab2) mutant identified in a pinoid (pid) enhancer mutant screen. Seedlings homozygous for either mab2 or pid showed only mild phenotypic effects on cotyledon positions and/or numbers. In contrast, mab2 pid double mutant seedlings completely lacked cotyledons, indicating a synergistic interaction. We found that mab2 homozygous embryos had defective patterns of cell division and showed aberrant cotyledon organogenesis. Further analysis revealed that the mab2 mutation affected auxin response but not auxin transport in the embryos, suggesting the involvement of MAB2 in auxin response during embryogenesis. MAB2 encodes an Arabidopsis ortholog of MED13, a putative regulatory module component of the Mediator complex. Mediator is a multicomponent complex that is evolutionarily conserved in eukaryotes and its regulatory module associates with Mediator to control the interaction of Mediator and RNA polymerase II. MAB2 interacts with a regulatory module component in yeast cells. Taken together, our data suggest that MAB2 plays a crucial role in embryo patterning and cotyledon organogenesis, possibly through modulating expression of specific genes such as auxin-responsive genes.
Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5, Takayama, Ikoma, Nara, 630-0101 Japan.
Jun
J
Ito
Takako
T
Sono
Masao
M
Tasaka
Masahiko
M
Furutani
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000187:drug effects / Q000196:embryology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019521:Body Patterning / Q000187:drug effects / Q000235:genetics; D018548:Cotyledon / Q000187:drug effects / Q000196:embryology* / Q000235:genetics; D056850:Cyclin-Dependent Kinase 8 / Q000378:metabolism; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant / Q000235:genetics; D007210:Indoleacetic Acids / Q000494:pharmacology; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D011485:Protein Binding / Q000187:drug effects; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012639:Seeds / Q000187:drug effects / Q000196:embryology* / Q000235:genetics; D017386:Sequence Homology, Amino Acid
D029681:Arabidopsis Proteins; D056850:Cyclin-Dependent Kinase 8; D007210:Indoleacetic Acids; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; C546591:GRAND CENTRAL protein, Arabidopsis; C522174:AT5G63610 protein, Arabidopsis