Defense-related signaling by interaction of arabinogalactan proteins and beta-glucosyl Yariv reagent inhibits gibberellin signaling in barley aleurone cells.
Arabinogalactan proteins (AGPs) are hydroxyproline-rich glycoproteins present at the plasma membrane and in extracellular spaces. A synthetic chemical, beta-glucosyl Yariv reagent (beta-GlcY), binds specifically to AGPs. We previously reported that gibberellin signaling is specifically inhibited by beta-GlcY treatment in barley aleurone protoplasts. In the present study, we found that beta-GlcY also inhibited gibberellin-induced programmed cell death (PCD) in aleurone cells. We examined the universality and specificity of the inhibitory effect of beta-GlcY on gibberellin signaling using microarray analysis and found that beta-GlcY was largely effective in repressing gibberellin-induced gene expression. In addition, >100 genes were up-regulated by beta-GlcY in a gibberellin-independent manner, and many of these were categorized as defense-related genes. Defense signaling triggered by several defense system inducers such as jasmonic acid and a chitin elicitor could inhibit gibberellin-inducible events such as alpha-amylase secretion, PCD and expression of some gibberellin-inducible genes in aleurone cells. Furthermore, beta-GlcY repressed the gibberellin-inducible Ca2+-ATPase gene which is important for gibberellin-dependent gene expression, and induced known repressors of gibberellin signaling, two WRKY genes and a NAK kinase gene. These effects of beta-GlcY were also phenocopied by the chitin elicitor and/or jasmonic acid. These results indicate that gibberellin signaling is under the regulation of defense-related signaling in aleurone cells. It is also probable that AGPs are involved in the perception of stimuli causing defense responses.
D003517:Cyclopentanes / Q000378:metabolism; D005685:Galactans / Q000378:metabolism*; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D005875:Gibberellins / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D005960:Glucosides / Q000378:metabolism / Q000494:pharmacology*; D001467:Hordeum / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D054883:Oxylipins / Q000378:metabolism; D010696:Phloroglucinol / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D040081:Protein Array Analysis; D015398:Signal Transduction / Q000187:drug effects*
D003517:Cyclopentanes; D005685:Galactans; D005875:Gibberellins; D005960:Glucosides; D054883:Oxylipins; D010940:Plant Proteins; C104977:Yariv reagent; C011006:jasmonic acid; D010696:Phloroglucinol; C005653:arabinogalactan