The Dof protein DAG1 mediates PIL5 activity on seed germination by negatively regulating GA biosynthetic gene AtGA3ox1.
We have previously shown that inactivation of the gene encoding the Arabidopsis thaliana transcription factor DOF AFFECTING GERMINATION 1 (DAG1) renders seed germination more sensitive to both phytochrome B (phyB) and gibberellins (GA). dag1 mutant seeds require less red (R) light fluence and a lower GA concentration than WT to germinate. Here, we show that inactivation of the gene PHYTOCHROME INTERACTING FACTOR 3-LIKE 5 (PIL5) results in down-regulation of DAG1. Inactivation of PIL5 in the dag1 mutant background further increased the germination potential of dag1 mutant seeds, supporting the suggestion that DAG1 is under the positive control of PIL5. Germination of dag1phyB seeds showed a reduced requirement of gibberellins as compared with phyB mutant seeds, both in the presence and in the absence of GA biosynthesis. Furthermore, the GA biosynthetic gene AtGA3ox1 is upregulated in dag1 seeds as compared with the WT, and DAG1 actually binds to the AtGA3ox1 promoter, as shown by chromatin immunoprecipitation experiments. Expression analysis at different time points confirms that AtGA3ox1 is directly regulated by DAG1, while suggesting that DAG1 is not a direct regulatory target of PIL5. Our data indicate that in the phyB pathway leading to seed germination, DAG1 negatively regulates GA biosynthesis and suggest that DAG1 acts downstream of PIL5. In addition, the analysis of hypocotyls of dag1 and phyB mutant plantlets, of plantlets overexpressing phyB in the dag1 mutant, as well as of dag1phyB double mutant suggests that DAG1 may act as a negative regulatory element downstream of phyB also in hypocotyl elongation.
Gabriele
Stefano
S
Istituto Pasteur Fondazione Cenci Bolognetti, Dipartimento di Genetica e Biologia Molecolare, Università La Sapienza, Piazzale Aldo Moro 5, 00185 Rome, Italy.
Rizza
Annalisa
A
Martone
Julie
J
Circelli
Patrizia
P
Costantino
Paolo
P
Vittorioso
Paola
P
D000040:Abscisic Acid / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects / Q000528:radiation effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects / Q000528:radiation effects; D018525:Germination; D005875:Gibberellins / Q000096:biosynthesis* / Q000494:pharmacology; D018546:Hypocotyl / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D015151:Immunoblotting; D047468:Immunoprecipitation; D008027:Light; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D051939:Phytochrome B / Q000235:genetics / Q000378:metabolism; D010937:Plant Growth Regulators / Q000096:biosynthesis / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012639:Seeds / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014867:Water / Q000378:metabolism / Q000494:pharmacology
D000040:Abscisic Acid; D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins; D005875:Gibberellins; D006899:Mixed Function Oxygenases; D051939:Phytochrome B; D010937:Plant Growth Regulators; D014157:Transcription Factors; D014867:Water; C407526:DAG1 protein, Arabidopsis; C497952:PHYB protein, Arabidopsis; C108186:gibberellin 3beta-hydroxylase; C508068:At2g20180 protein, Arabidopsis