Gibberellin research has its origins in Japan in the 19th century, when a disease of rice was shown to be due to a fungal infection. The symptoms of the disease including overgrowth of the seedling and sterility were later shown to be due to secretions of the fungus Gibberella fujikuroi (now reclassified as Fusarium fujikuroi), from which the name gibberellin was derived for the active component. The profound effect of gibberellins on plant growth and development, particularly growth recovery in dwarf mutants and induction of bolting and flowering in some rosette species, prompted speculation that these fungal metabolites were endogenous plant growth regulators and this was confirmed by chemical characterisation in the late 1950s. Gibberellins are now known to be present in vascular plants, and some fungal and bacterial species. The biosynthesis of gibberellins in plants and the fungus has been largely resolved in terms of the pathways, enzymes, genes and their regulation. The proposal that gibberellins act in plants by removing growth limitation was confirmed by the demonstration that they induce the degradation of the growth-inhibiting DELLA proteins. The mechanism by which this is achieved was clarified by the identification of the gibberellin receptor from rice in 2005. Current research on gibberellin action is focussed particularly on the function of DELLA proteins as regulators of gene expression. This review traces the history of gibberellin research with emphasis on the early discoveries that enabled the more recent advances in this field.

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Some chemosensory proteins (CSPs) are expressed in insect sensory appendages and are thought to be involved in chemical signaling by ants. We identified fourteen unique CSP sequences in EST libraries of the red imported fire ant, Solenopsis invicta. One member of this group (Si-CSP1) is highly expressed in worker antennae, suggesting an olfactory function. A shotgun proteomic analysis of antennal proteins confirms the high level of Si-CSP1 expression, and also shows expression of another CSP and two odorant-binding proteins (OBPs). We cloned and expressed the coding sequence for Si-CSP1. We used cyclodextrins as solubilizers to investigate ligand binding. Fire ant cuticular lipids strongly inhibit Si-CSP1 binding to the fluorescent dye N-phenyl-naphthylamine, suggesting cuticular substances are ligands for Si-CSP1. Analysis of the cuticular lipids shows that the endogenous ligands of Si-CSP1 are not cuticular hydrocarbons.

Gibberellin A20 (GA20), GA29 and GA29-catabolite were quantified in cotyledons, embryonic axes, and testas of Pisum sativum cv. Progress No. 9 throughout the final stages of seed maturation and during germination. Stable isotope-labelled GAs were used as internal standards in conjunction with combined gas chromatography-mass spectrometry. Gibberellin A20 and GA29 were mainly located in the cotyledons of maturing seeds, and GA29-catabolite was predominantly located in the testa. Stable isotope- and radio-labelled GA20 and GA29 were fed to both intact seeds developing in vivo, and to isolated seed parts cultured in vitro. The combined results of in-vivo and in-vitro feeds indicated that GA20 is metabolised to GA29 in the cotyledons, that GA29 is transported from the cotyledons to the testa, and that GA29 is metabolised to GA29-catabolite in the testa. Although the metabolism of GA20 in the cotyledons and of GA29 in the testa has been shown definitively, the mobility of GA29 has not yet been demonstrated directly. During seed desiccation and germination GA29-catabolite and products arising from it are transferred from the testa into the embryo. There is no evidence of a physiological function for GA29-catabolite in germination or early seedling growth. Use of a growth retardant indicates that seedling growth, but not germination, is dependent on de-novo GA biosynthesis.

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