ABSTRACT
Amino acid homeostasis in plants is finely tuned to match developmental needs and response to adverse environments. Over-expression of the single-transmembrane domain protein GLUTAMINE DUMPER1 (GDU1) leads to increased amino acid export, reduced growth and constitutive induction of immune responses. We used an inducible gene expression system to tease apart the primary and secondary effects caused by GDU1, and demonstrated that the primary effect is increasing amino acid export, followed by increased amino acid content and abscisic acid (ABA) response, and a subsequent activation of defense responses. The GDU1-mediated hypersensitivity to ABA partially depended on the E3 ubiquitin ligase LOSS-OF-GDU1 2 (LOG2), a known GDU1 interactor. More importantly, the lysine catabolite pipecolic acid played a pivotal role in the GDU1-induced defense responses. This work unravels a novel relationship between amino acid transport, ABA and defense responses, potentially mediated by the GDU1-LOG2 complex, critical for understanding how plants respond to amino acid imbalance.
ONE SENTENCE SUMMARY Genetically induced disturbance of amino acid homeostasis sequentially triggers responses to abiotic stresses and plant defenses to pathogens in Arabidopsis through undefined sensing mechanisms
Footnotes
S.Y., R.G and G.P. conceived and coordinated the study; S.Y. and G.P. performed experiments; K.H. and Y.S. developed the method and analyzed the hormone content in plant extract using LC-MS; D.A. and S.Y. analyzed the RNAseq data; E.C. and Y.S. ran the amino acid analyses; Y.S and G.P wrote the manuscript; all authors read and approved the final article; R.G. and G.P secured funding; G.P. agrees to serve as the author responsible for contact and ensures communication.
This work was supported by a startup package from Virginia Tech, the Virginia Agricultural Experiment Station and the Hatch Program of the National Institute of Food and Agriculture, U.S. Department of Agriculture, project VA-135908, VA-160087 (GP), and the National Science Foundation (USA), grants MCB-1052048 and IOS-1353366 (GP), and MCB-1052145 (RG).