Analysis of Flagellin Perception Mediated by flg22 Receptor OsFLS2 in Rice

Abstract

Plants have sensitive perception systems that recognize various pathogen-derived molecules. We previously reported that rice detects flagellin from a rice-incompatible strain of gram-negative phytopathogenic bacterium, Acidovorax avenae, which induces subsequent immune responses involving cell death. The mechanism of flagellin perception in rice, however, has remained obscure. In this study, we found that flg22, a peptide derived from the flagellin N-terminus, induced weak immune responses without cell death in cultured rice cells. To elucidate the mechanism by which flg22 induced signaling in rice, we characterized OsFLS2, the rice ortholog of AtFLS2, which mediates flg22 perception. Heterologous expression of OsFLS2 functions in Arabidopsis, showing the conservation of the flg22 signaling pathway across divergent plant taxa. OsFLS2-overexpressing rice cultured cells generated stronger immune responses with the induction of cell death following stimulation with flg22 and flagellin. However, examination of the growth rate of the compatible strain in inoculated OsFLS2-overexpressing rice could not confirm bacterial growth suppression compared with wild-type rice. These results suggest that rice possesses a conserved flagellin perception system utilizing the FLS2 receptor which, when upregulated, hardly affects resistance against compatible A. avenae.

Defense responses in female gametophytes of Saccharina japonica (Phaeophyta) induced by flg22-derived peptides

“…H 2 O 2 detection and quantification H 2 O 2 was monitored by measuring luminol-dependent luminescence ascribable to ferricyanide-catalyzed oxidation according to a previous method described by Takai et al (2008) and Wang et al (2013). Twenty microliters of incubated gametophytes was mixed with 150 μL of 10 mM potassium phosphate buffer (pH 7.8), 20 μL of 14 mM potassium ferricyanide, and 10 μL of 1.1 mM luminol solution; then, the samples were placed in a luminometer (GloMax 20/20, Promega, USA) and analyzed for chemiluminescence immediately.…”

Recent Advances in PAMP-Triggered Immunity against Bacteria: Pattern Recognition Receptors Watch over and Raise the Alarm

“…Rice (Oryza sativa) was reported to be insensitive to flg22 . However, recent results showed that flg22 is recognized by rice but that this response is weaker than with full-length flagellin (Takai et al, 2008). A shorter version of the flg22 peptide, called flg15, acts as an antagonist in Arabidopsis (Arabidopsis thaliana), while it is fully active in tomato (Solanum lycopersicum; Meindl et al, 2000;Bauer et al, 2001;Robatzek et al, 2007).…”

Probing the Arabidopsis Flagellin Receptor: FLS2-FLS2 Association and the Contributions of Specific Domains to Signaling Function

“…FLS2 is the pattern recognition receptor that mediates plant basal defenses triggered by bacterial flagellin, a microbeassociated molecular pattern (MAMP) (Gó mez-Gó mez and Boller, 2000). The flg22 region within the conserved N terminus of bacterial flagellins carries the elicitation determinant of bacterial flagellin that is recognized by many plants Sun et al, 2006;Robatzek et al, 2007;Takai et al, 2008). FLS2 directly binds flg22 .…”