HLM1, an Essential Signaling Component in the Hypersensitive Response, Is a Member of the Cyclic Nucleotide–Gated Channel Ion Channel Family[W]

Abstract

The hypersensitive response (HR) in plants is a programmed cell death that is commonly associated with disease resistance. A novel mutation in Arabidopsis, hlm1 , which causes aberrant regulation of cell death, manifested by a lesionmimic phenotype and an altered HR, segregated as a single recessive allele. Broad-spectrum defense mechanisms remained functional or were constitutive in the mutant plants, which also exhibited increased resistance to a virulent strain of Pseudomonas syringae pv tomato . In response to avirulent strains of the same pathogen, the hlm1 mutant showed differential abilities to restrict bacterial growth, depending on the avirulence gene expressed by the pathogen. The HLM1 gene encodes a cyclic nucleotide-gated channel, CNGC4 . Preliminary study of the HLM1/CNGC4 gene product in Xenopus oocytes (inside-out patch-clamp technique) showed that CNGC4 is permeable to both K ؉ and Na ؉ and is activated by both cGMP and cAMP. HLM1 gene expression is induced in response to pathogen infection and some pathogen-related signals. Thus, HLM1 might constitute a common downstream component of the signaling pathways leading to HR/resistance.

Overexpression of DWARF AND LESION FORMATION 1 (DLE1) causes altered activation of plant defense system in Arabidopsis thaliana

“…These results suggested that the molecular pathway for the defense response was activated in DLE1OX. This is supported by the correlation between the expression levels of DLE1 and the severity of the abnormal dwarfism in DLE1OX (Figure 2B), because enhancement of the Copyright © 2013 The Japanese Society for Plant Cell and Molecular Biology defense response frequently causes defects in plant growth (Balague et al 2003;Bowling et al 1994;Dietrich et al 1994;Gou et al 2009;Greenberg et al 1994). Interestingly, many genes, which are involved in cell wall organization according to gene ontology annotation, were included in the overexpressed genes by microarray.…”

“…The lesions in the leaves of some defense-related mutants simulate the phenomenon known as the hypersensitive response (HR), which is characterized by programmed cell death (Balague et al 2003;Bowling et al 1994;Dietrich et al 1994;Gou et al 2009;Greenberg et al 1994). Since it was confirmed that cell death occurred in these leaf areas, DLE1OX lines show HR-like lesion formation ( Figure 3B).…”

“…Moreover, various growth hormones including SA, abscisic acid (ABA), JA, ET and brassinosteroids (BRs) and abiotic stresses also regulate these genes (Mauch-Mani and Mauch 2005;Thomma et al 2001). In some defense-related Arabidopsis mutants such as the constitutive expresser of PR genes (cpr), accelerated cell death (acd), lesion simulating disease resistance response (lsd) and HR-like lesion mimic (hlm1), PR genes are constitutively expressed (Balague et al 2003;Bowling et al 1994;Dietrich et al 1994;Gou et al 2009;Greenberg et al 1994). The defense responses of these mutants showing HR-like lesion formation and constitutive SAR-like defense responses are constitutively active in the absence of pathogen infection.…”

Maltose-binding protein switches programmed cell death in Nicotiana glutinosa leaf cells

“…Arabidopsis dnd1 gene encodes a cyclic nucleotide-gated channel (CNGC) family which act as calcium channel regulates HR phenomenon positively [13]. hlm1 gene encodes transporter of K + and Na + channel that induces HR [14].…”

“…Almost, all of the stimuli and molecular signals that activate programmed cell death are similar in all organisms. On the molecular level, activation of certain transcriptional factors [30], induction of enzymes involved in protein metabolism [31,32], DNA degradation [11], lipids metabolism [17], phytohormone synthesis [7,8], ROS production [33] and ion homeostasis alterations [13,14] have been characterized, so far.…”