Overexpression in Arabidopsis of a plasma membrane-targeting glutamate receptor from small radish increases glutamate-mediated Ca2+ influx and delays fungal infection.
Ionotropic glutamate receptors (iGluRs) are ligand-gated nonselective cation channels that mediate fast excitatory neurotransmission. Although homologues of the iGluRs have been identified in higher plants, their roles are largely unknown. In this work we isolated a full-length cDNA clone (RsGluR) encoding a putative glutamate receptor from small radish. An RsGluR: mGFP fusion protein was localized to the plasma membrane. In Arabidopsis thaliana overexpressing the full-length cDNA, glutamate treatment triggered greater Ca2+ influx in the root cells of transgenic seedlings than in those of the wild type. Transgenic plants exhibited multiple morphological changes such as necrosis at their tips and the margins of developing leaves, dwarf stature with multiple secondary inflorescences, and retarded growth, as previously observed in transgenic Arabidopsis overexpressing AtGluR3.2 [Kim et al. (2001)]. Microarray analysis showed that jasmonic acid (JA)-responsive genes including defensins and JA-biosynthetic genes were up-regulated. RsGluR overexpression also inhibited growth of a necrotic fungal pathogen Botrytis cinerea possibly due to up-regulation of the defensins. Based on these results, we suggest that RsGluR is a glutamate-gated Ca2+ channel located in the plasma membrane of higher plants and plays a direct or indirect role in defense against pathogen infection by triggering JA biosynthesis.
Kang
Seock
S
Department of Biological Sciences, Seoul National University, Seoul 151-747, Korea.
Kim
Ho Bang
HB
Lee
Hyoungseok
H
Choi
Jin Young
JY
Heu
Sunggi
S
Oh
Chang Jae
CJ
Kwon
Soon Il
SI
An
Chung Sun
CS
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism / Q000382:microbiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D003001:Cloning, Molecular; D003517:Cyclopentanes / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D018698:Glutamic Acid / Q000378:metabolism*; D046228:Microarray Analysis; D008969:Molecular Sequence Data; D054883:Oxylipins; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology; D030821:Plants, Genetically Modified; D031224:Raphanus / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology*; D017470:Receptors, Glutamate / Q000235:genetics / Q000378:metabolism*; D013347:Subcellular Fractions
D029681:Arabidopsis Proteins; D003517:Cyclopentanes; D054883:Oxylipins; D017470:Receptors, Glutamate; D018698:Glutamic Acid; C011006:jasmonic acid; D002118:Calcium