Evolutionary conservation of plant gibberellin signalling pathway components.
BACKGROUND
Gibberellins (GA) are plant hormones that can regulate germination, elongation growth, and sex determination. They ubiquitously occur in seed plants. The discovery of gibberellin receptors, together with advances in understanding the function of key components of GA signalling in Arabidopsis and rice, reveal a fairly short GA signal transduction route. The pathway essentially consists of GID1 gibberellin receptors that interact with F-box proteins, which in turn regulate degradation of downstream DELLA proteins, suppressors of GA-controlled responses.


RESULTS
Arabidopsis sequences of the gibberellin signalling compounds were used to screen databases from a variety of plants, including protists, for homologues, providing indications for the degree of conservation of the pathway. The pathway as such appears completely absent in protists, the moss Physcomitrella patens shares only a limited homology with the Arabidopsis proteins, thus lacking essential characteristics of the classical GA signalling pathway, while the lycophyte Selaginella moellendorffii contains a possible ortholog for each component. The occurrence of classical GA responses can as yet not be linked with the presence of homologues of the signalling pathway. Alignments and display in neighbour joining trees of the GA signalling components confirm the close relationship of gymnosperms, monocotyledonous and dicotyledonous plants, as suggested from previous studies.


CONCLUSIONS
Homologues of the GA-signalling pathway were mainly found in vascular plants. The GA signalling system may have its evolutionary molecular onset in Physcomitrella patens, where GAs at higher concentrations affect gravitropism and elongation growth.
Vandenbussche
Filip
F
Unit Plant Hormone Signaling & Bio-imaging, Department of Molecular Genetics, Ghent University, Ledeganckstraat 35, B-9000 Ghent, Belgium. Filip.Vandenbussche@ugent.be
Fierro
Ana C
AC
Wiedemann
Gertrud
G
Reski
Ralf
R
Van Der Straeten
Dominique
D
D000595:Amino Acid Sequence; D019068:Bryopsida / Q000187:drug effects / Q000235:genetics / Q000254:growth & development; D019295:Computational Biology; D030541:Databases, Genetic; D019143:Evolution, Molecular; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D005875:Gibberellins / Q000378:metabolism / Q000494:pharmacology; D008969:Molecular Sequence Data; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D018514:Plant Structures / Q000187:drug effects / Q000235:genetics / Q000254:growth & development; D011956:Receptors, Cell Surface / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics*
D005875:Gibberellins; D010940:Plant Proteins; D011956:Receptors, Cell Surface