Expression analysis of a GA 20-oxidase in embryos from two sorghum lines with contrasting dormancy: possible participation of this gene in the hormonal control of germination.
The role of GAs in promoting seed germination is well known and experiments with seeds from different species have suggested the requirement of de novo synthesis of GAs upon imbibition for germination. There are also strong indications that the enhancement of GA synthesis is part of the mechanism through which environmental signals (i.e. light) induce germination. Since along the GA biosynthetic pathway, oxidation at C-20 carried out by GA 20-oxidases is thought to be a site of regulation, a cDNA clone encoding a GA 20-oxidase was isolated from embryos of sorghum (SbGA 20ox). Expression analysis of this gene in embryos within imbibed caryopses with low dormancy showed detectable amounts of the specific mRNA early upon incubation, increasing thereafter. In contrast, it remained barely detectable in embryos from dormant caryopses. Changes in endogenous GA4 levels were in agreement with those of SbGA 20ox mRNA, suggesting that GA production might be regulated differentially at the level of transcription of this gene. The expression of SbGA 20ox was enhanced in incubated embryos isolated from either type of caryopses, illustrating a physiological control exerted by the surrounding seed tissues on gene expression. The results also show that ABA leads to a suppression of transcription of this gene.
Pérez-Flores
Laura
L
UAM-Iztapalapa, México.
Carrari
Fernando
F
Osuna-Fernández
Reyna
R
Rodríguez
M Verónica
MV
Enciso
Silvina
S
Stanelloni
Roberto
R
Sanchez
Rodolfo A
RA
Bottini
Rubén
R
Iusem
Norberto D
ND
Benech-Arnold
Roberto L
RL
D000595:Amino Acid Sequence; D015139:Blotting, Southern; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D006899:Mixed Function Oxygenases / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D010937:Plant Growth Regulators / Q000494:pharmacology; D006109:Poaceae / Q000187:drug effects / Q000201:enzymology / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D012639:Seeds / Q000201:enzymology* / Q000235:genetics; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity
D010937:Plant Growth Regulators; D012333:RNA, Messenger; D006899:Mixed Function Oxygenases; C089210:gibberellin, 2-oxoglutarate-oxygen oxidoreductase (20-hydroxylating, oxidizing)