title: Saltational evolution of the heterotrimeric G protein signaling mechanisms in the plant kingdom.
abstract: Signaling proteins evolved diverse interactions to provide specificity for distinct stimuli. Signaling complexity in the G protein (heterotrimeric guanosine triphosphate-binding protein) network was achieved in animals through subunit duplication and incremental evolution. By combining comprehensive and quantitative phenotypic profiles of Arabidopsis thaliana with protein evolution informatics, we found that plant heterotrimeric G protein machinery evolved by a saltational (jumping) process. Sequence similarity scores mapped onto tertiary structures, and biochemical validation showed that the extra-large Gα (XLG) subunit evolved extensively in the charophycean algae (an aquatic green plant) by gene duplication and gene fusion. In terrestrial plants, further evolution uncoupled XLG from its negative regulator, regulator of G protein signaling, but preserved an α-helix region that enables interaction with its partner Gβγ. The ancestral gene evolved slowly due to the molecular constraints imposed by the need for the protein to maintain interactions with various partners, whereas the genes encoding XLG proteins evolved rapidly to produce three highly divergent members. Analysis of A. thaliana mutants indicated that these Gα and XLG proteins all function with Gβγ and evolved to operate both independently and cooperatively. The XLG-Gβγ machinery specialized in environmental stress responses, whereas the canonical Gα-Gβγ retained developmental roles. Some developmental processes, such as shoot development, involve both Gα and XLG acting cooperatively or antagonistically. These extensive and rapid evolutionary changes in XLG structure compared to those of the canonical Gα subunit contrast with the accepted notion of how pathway diversification occurs through gene duplication with subsequent incremental coevolution of residues among interacting proteins.
authors.affiliation: Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA. Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, Singapore 117604, Singapore. daisuke@tll.org.sg alan_jones@unc.edu.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Urano
authors.affiliation: Plant Genetic Engineering Laboratory, School of Agriculture and Food Sciences, University of Queensland, Brisbane, Queensland 4072, Australia.
authors.forename: Natsumi
authors.initials: N
authors.lastname: Maruta
authors.affiliation: Plant Genetic Engineering Laboratory, School of Agriculture and Food Sciences, University of Queensland, Brisbane, Queensland 4072, Australia.
authors.forename: Yuri
authors.initials: Y
authors.lastname: Trusov
authors.affiliation: Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA.
authors.forename: Richard
authors.initials: R
authors.lastname: Stoian
authors.affiliation: Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA.
authors.forename: Qingyu
authors.initials: Q
authors.lastname: Wu
authors.affiliation: Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA.
authors.forename: Ying
authors.initials: Y
authors.lastname: Liang
authors.affiliation: Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA.
authors.forename: Dinesh Kumar
authors.initials: DK
authors.lastname: Jaiswal
authors.affiliation: Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, Singapore 117604, Singapore.
authors.forename: Leena
authors.initials: L
authors.lastname: Thung
authors.affiliation: Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA.
authors.forename: David
authors.initials: D
authors.lastname: Jackson
authors.affiliation: Plant Genetic Engineering Laboratory, School of Agriculture and Food Sciences, University of Queensland, Brisbane, Queensland 4072, Australia.
authors.forename: José Ramón
authors.initials: JR
authors.lastname: Botella
authors.affiliation: Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA. Department of Pharmacology, University of North Carolina, Chapel Hill, NC 27599, USA. daisuke@tll.org.sg alan_jones@unc.edu.
authors.forename: Alan M
authors.initials: AM
authors.lastname: Jones
mesh_terms: D017360:Arabidopsis; D019143:Evolution, Molecular; D019204:GTP-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D047008:Marchantia / Q000235:genetics* / Q000378:metabolism; D028222:Picea / Q000235:genetics* / Q000378:metabolism; D041603:Pinus taeda / Q000235:genetics* / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D010940:Plant Proteins; D019204:GTP-Binding Proteins