A novel pepper membrane-located receptor-like protein gene
CaMRP1 is required for disease susceptibility, methyl jasmonate
insensitivity and salt tolerance
Soo Hyun An Æ Hyong Woo Choi Æ In Sun Hwang Æ
Jeum Kyu Hong Æ Byung Kook Hwang
Received: 3 October 2007 / Accepted: 9 April 2008 / Published online: 22 April 2008
Ó Springer Science+Business Media B.V. 2008
Abstract Plant receptor proteins are involved in the
signaling networks required for defense against pathogens.
The novel pepper pathogen-induced gene CaMRP1 was
isolated from pepper leaves infected with Xanthomonas
campestris pv. vesicatoria (Xcv). This gene is predicted to
encode a membrane-located receptor-like protein that has
an N-terminal signal peptide and a C-terminal transmem-
brane helix. A CaMRP1-GFP fusion protein localized
primarily to the plasma membrane of plant cells. Strong
and early induction of CaMRP1 expression occurred fol-
lowing exposure of pepper plants to Xcv, Colletotricum
coccodes, methyl jasmonate (MeJA) and wounding stress.
Virus-induced gene silencing (VIGS) of CaMRP1 in pep-
per conferred enhanced basal resistance to Xcv infection,
accompanied by induction of genes encoding basic PR1
(CaBPR1), defensin (CaDEF1) and SAR8.2 (CaSAR82A).
In contrast, CaMRP1 overexpression (OX) in transgenic
Arabidopsis plants resulted in increased disease suscepti-
bility to Hyaloperonospora parasitica infection.
Arabidopsis plants overexpressing CaMRP1 exhibited
insensitivity to MeJA by causing reduced expression of
MeJA-responsive genes. Overexpression also resulted in
tolerance to NaCl and during salt stress, the expression of
several abscisic acid-responsive genes was induced.
Together, these results suggest that pepper CaMRP1 may
belong to a new subfamily of membrane-located receptor-
like proteins that regulate disease susceptibility, MeJA-
insensitivity and salt tolerance.
Keywords Disease susceptibility Á
Membrane-located receptor-like protein Á
Methyl jasmonate Á Pepper Á Salt stress
The plant cell membrane encloses the cell contents and
separates them from the surrounding environment. Essen-
tial proteins that have receptor domains on either side of
the membrane control cell-signaling responses to a large
variety of environmental stimuli (Breton et al. 2003).
These membrane proteins can recognize and transport
signals relating to environmental changes, such as patho-
gen infection, drought, high salinity and cold stress.
Recent investigation into the innate immunity of plants
has indicated that numerous membrane-located proteins are
associated with the recognition of pathogen attack (Nurn-
berger et al. 2004). These membrane proteins interact with
different pathogen factors and following pathogen recog-
nition, various host molecules such as protein kinases and
transcription factors relay signals to activate downstream
defense responses. For instance, the membrane-anchored
protein Botrytis-induced kinase1 (BIK1) transcriptionally
regulates Arabidopsis resistance to Botrytis cinerea and
inactivation of the gene encoding this protein causes
extreme susceptibility to the necrotic fungal pathogens B.
cinerea and Alternaria brassicicola (Veronese et al. 2006).
The plasma membrane-localized
cell death 6 (ACD6) protein, which comprises an ankyrin-
repeat domain and a predicted transmembrane region, is
believed to be a positive regulator in Arabidopsis defense
The nucleotide sequence data reported here has been deposited in the
GenBank database under the accession number EU181138.
S. H. An Á H. W. Choi Á I. S. Hwang Á J. K. Hong Á
B. K. Hwang (&)
Laboratory of Molecular Plant Pathology, School of Life
Sciences and Biotechnology, Korea University, Anam-dong,
Sungbuk-ku, Seoul 136-713, Republic of Korea
Plant Mol Biol (2008) 67:519–533