GTP binding by Arabidopsis extra-large G protein 2 is not essential for its functions

Natsumi Maruta, Yuri Trusov, Daisuke Urano, David Chakravorty, Sarah M. Assmann, Alan M. Jones, Jose R. Botella

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


The extra-large guanosine-50-triphosphate (GTP)-binding protein 2, XLG2, is an unconventional Ga subunit of the Arabidopsis (Arabidopsis thaliana) heterotrimeric GTP-binding protein complex with a major role in plant defense. In vitro biochemical analyses and molecular dynamic simulations show that affinity of XLG2 for GTP is two orders of magnitude lower than that of the conventional Ga, AtGPA1. Here we tested the physiological relevance of GTP binding by XLG2. We generated an XLG2(T476N) variant with abolished GTP binding, as confirmed by in vitro GTPcS binding assay. Yeast three-hybrid, bimolecular fluorescence complementation, and split firefly-luciferase complementation assays revealed that the nucleotide-depleted XLG2(T476N) retained wild-type XLG2-like interactions with the Gbc dimer and defense-related receptor-like kinases. Both wild-type and nucleotide-depleted XLG2(T476N) restored the defense responses against Fusarium oxysporum and Pseudomonas syringae compromised in the xlg2 xlg3 double mutant. Additionally, XLG2(T476N) was fully functional restoring stomatal density, root growth, and sensitivity to NaCl, but failed to complement impaired germination and vernalization-induced flowering. We conclude that XLG2 is able to function in a GTP-independent manner and discuss its possible mechanisms of action.

Original languageEnglish (US)
Pages (from-to)1240-1253
Number of pages14
JournalPlant physiology
Issue number2
StatePublished - Jun 2021

All Science Journal Classification (ASJC) codes

  • Physiology
  • Genetics
  • Plant Science


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