Evidence of a cross‐talk regulation of a GA 20‐oxidase (FsGA20ox1) by gibberellins and ethylene during the breaking of dormancy in Fagus sylvatica seeds

Abstract

Gibberellin 20-oxidase (GA 20-oxidase) is an enzyme that catalyses the last three steps in the synthesis of active GAs and is a potential control point in the regulation of GA biosynthesis. Reverse transcriptase-polymerase chain reaction with degenerated oligonucleotides conserved among GA 20-oxidases was used to isolate a cDNA clone for this enzyme in Fagus sylvatica L. seeds. This clone contains all the features and exhibits homology to GA 20 oxidases from several plant species. Expression of this clone, named FsGA20ox1, as a fusion protein expressed in Escherichia coli confirmed that it was able to metabolize [(14)C]GA(12) to [(14)C]GA(9) and [(14)C]GA(53) to [(14)C]GA(20). Analysis of FsGA20ox1 transcript levels showed similar low expression during stratification at 4 degrees C and in the presence of gibberellic acid or ethephon (compound that releases ethylene in solution), treatments proved to be efficient in breaking the dormancy of beech seeds. However, there was a drastic increase of FsGA20ox1 transcript levels in the presence of paclobutrazol (PCB), a well-known GAs biosynthesis inhibitor, or of 2-aminoxyacetic acid (AOA), an inhibitor of ethylene biosynthesis. Furthermore, the effect of AOA was reversed by the addition of GA(3) and that of PCB by ethephon. This indicates that the gene product is subjected to down-regulation by GA and ethylene, and further suggests a cross-talk gene regulation by these two hormones during the transition from seed dormancy to germination.

Contrasting relationships between the diversity of candidate genes and variation of bud burst in natural and segregating populations of European oaks

“…Additional CGs were selected based on their functional role known from other plants. As gibberellins are known to be implied in bud flushing (Or et al, 2000;Falusi and Calamassi, 2003), we included Gibberellin 20-oxidase (GA20) and Gibberellin 3-b-hydroxylase (GA3) (PerezFlores et al, 2003;Calvo et al, 2004;Israelsson et al, 2004), which are involved in the synthesis of GA1, the active form of gibberellins in plants. Additionally, we selected 15 microsatellite loci as 'control markers' that would picture the existing geographic structure for neutral markers (Mariette et al, 2002).…”

Contrasting relations between diversity of candidate genes and variation of bud burst in natural and segregating populations of European oaks

“…Additional CGs were selected based on their functional role known from other plants. As gibberellins are known to be implied in bud flushing (Or et al, 2000;Falusi and Calamassi, 2003), we included Gibberellin 20-oxidase (GA20) and Gibberellin 3-b-hydroxylase (GA3) (Perez-Flores et al, 2003;Calvo et al, 2004;Israelsson et al, 2004), which are involved in the synthesis of GA1, the active form of gibberellins in plants.…”

Participation of GA3, ethylene, NO and HCN in germination of Amaranthus retroflexus L. seeds with various dormancy levels

“…Releasing dormancy in A. retroflexus seeds by GA 3 involved the biosynthesis of ethylene and its action (Kępczyński et al 2003b). It was found that the expression of SoACO2 was inhibited by (Calvo et al 2004). On the other hand, GA 3 enhanced ACC oxidase gene, ACC content and ethylene production.…”