Overview of Proteins in Plant Hormone Signaling
Plant hormones are a set of small organic compounds that play a key role in plant growth, development, and responses to environmental signals. In addition to these conventional hormones, recent studies have revealed physiologically crucial roles of peptide hormones. Plant hormone receptors comprise different types of proteins including F-box proteins, an adaptor protein of F-box protein, a protein phosphatase inhibitor, histidine kinases, and Ser/Thr receptor kinases. In certain cases, receptors of gibberellin, strigolactone and karrikin are folded into α/β hydrolase folds, and the strigolactone and karrikin receptors possess a conserved catalytic triad system and preserved hydrolase activity. Plant hormones are allosteric inducers that induce conformational changes in receptors upon hormone perception to switch on or facilitate the transfer of signals to downstream effector proteins. To accomplish the switch function, plant hormone receptors adopt several mechanisms such as the “molecular glue” mechanism of the auxin and jasmonate receptors, or the “close-the-lid” and the “gate-latch-lock” mechanisms of the gibberellin and abscisic acid receptors, respectively. The brassinosteroid receptor and certain peptide receptors also adopt the “molecular glue” mechanism for co-receptor binding.
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