title: The alpha-subunit of the heterotrimeric G-protein affects jasmonate responses in Arabidopsis thaliana.
abstract: Heterotrimeric G-proteins have been implicated in having a role in many plant signalling pathways. To understand further the role of G-proteins, a preliminary experiment was performed to assess the impact of the G alpha subunit loss-of-function mutation gpa1-1 on the Arabidopsis transcriptome. The analysis indicated that the G alpha subunit may play a role in response to jasmonic acid (JA). Consistent with this, G alpha mutants showed a reduced response to JA in inhibition of chlorophyll accumulation and root growth, whilst G alpha gain-of-function plants overexpressing G alpha showed the opposite phenotype. The levels of JA and related compounds were unaffected in the gpa1-1 mutant, as was autoregulation of the Allene Oxide Synthase (AOS) gene that encodes a key enzyme for JA biosynthesis. In contrast, further analyses using G alpha loss- and gain-of-function Arabidopsis lines indicated that G alpha positively modulates the expression of the Vegetative Storage Protein (VSP) gene. This indicates that the G alpha subunit regulates a subset of JA-regulated genes defining a branch point in this signalling pathway in Arabidopsis. Further analysis of the impact of G alpha loss of function upon the JA-regulated transcriptome using Arabidopsis full genome arrays indicated that up to 29% of genes that are >2-fold regulated by JA in the wild type are misregulated in the G alpha mutant. This supports the observation that a significant proportion of, but not all, JA-regulated gene expression is mediated by G alpha.
authors.affiliation: Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK. haruko.okamoto@plants.ox.ac.uk
authors.forename: Haruko
authors.initials: H
authors.lastname: Okamoto
authors.forename: Cornelia
authors.initials: C
authors.lastname: Göbel
authors.forename: Richard G
authors.initials: RG
authors.lastname: Capper
authors.forename: Nigel
authors.initials: N
authors.lastname: Saunders
authors.forename: Ivo
authors.initials: I
authors.lastname: Feussner
authors.forename: Marc R
authors.initials: MR
authors.lastname: Knight