Expression analysis of the AtMLO gene family encoding
plant-specific seven-transmembrane domain proteins
Zhongying Chen
1
, H. Andreas Hartmann
2
, Ming-Jing Wu
1
, Erin J. Friedman
1
,
Jin-Gui Chen
1,4
, Matthew Pulley
1
, Paul Schulze-Lefert
2
, Ralph Panstruga
2
and Alan M. Jones
1,3,
*
1
Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
(*author for correspondence; e-mail alan_jones@unc.edu);
2
Department of Plant–Microbe Interactions,
Max-Planck Institute for Plant Breeding Research, Carl-von-Linne
´
-Weg 10, Cologne, D-50829, Germany;
3
Department of Pharmacology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599,
USA;
4
Department of Botany, University of British Columbia, 6270 University Boulevard, Vancouver, B.C.
V6T 1Z4, Canada
Received 28 June 2005; accepted in revised form 12 November 2005
Key words: Arabidopsis thaliana, GUS staining, heterotrimeric G-protein, microarray, MLO, RT-PCR
Abstract
The Arabidopsis (Arabidopsis thaliana) genome contains 15 genes encoding protein homologs of the barley
mildew resistance locus o (MLO) protein biochemically shown to have a seven-transmembrane domain
topology and localize to the plasma membrane. Towards elucidating the functions of MLOs, the largest
family of seven-transmembrane domain proteins specific to plants, we comprehensively determined AtMLO
gene expression patterns by a combination of experimental and in silico studies. Experimentation comprised
analyses of transgenic Arabidopsis lines bearing promoter::b-glucuronidase (GUS) transcriptional fusions
as well as semi-quantitative determination of transcripts by reverse transcription coupled to polymerase
chain reaction (RT-PCR). These results were combined with information extracted from public gene
profiling databases, and compared to the expression patterns of genes encoding the heterotrimeric
G-protein subunits. We found that each AtMLO gene has a unique expression pattern and is regulated
differently by a variety of biotic and/or abiotic stimuli, suggesting that AtMLO proteins function in diverse
developmental and response processes. The expression of several phylogenetically closely-related AtMLO
genes showed similar or overlapping tissue specificity and analogous responsiveness to external stimuli,
suggesting functional redundancy, co-function, or antagonistic function(s).
Abbreviations: AGB1, the Arabidopsis Gb subunit; AGG1, the Arabidopsis Gc subunit1; AGG2, the
Arabidopsis Gc subunit2; FRET, Fo
¨
rster/Fluorescence Resonance Energy Transfer; GCR1, G-Coupled
Receptor1; GPA1, the Arabidopsis Ga subunit; GPCRs, G-protein coupled receptors; GUS, b-glucuron-
idase; MLO, mildew resistance locus o; RGS1, Regulator of G-protein Signaling; 7TM, seven-
transmembrane
Introduction
Multi-cellular organisms evolved mechanisms to
sense both intra- and extra-cellular signals to
achieve coordinated development and to respond
properly to environmental cues. The seven-trans-
membrane (7TM) domain G-protein coupled recep-
tors (GPCRs), which link diverse extracellular
Plant Molecular Biology (2006) 60:583–597 Ó Springer 2006
DOI 10.1007/s11103-005-5082-x