Induction of host defences by Rhizobium during ineffective nodulation of pea (Pisum sativum L.) carrying symbiotically defective mutations sym40 (PsEFD), sym33 (PsIPD3/PsCYCLOPS) and sym42.
Rhizobia are able to establish a beneficial interaction with legumes by forming a new organ, called the symbiotic root nodule, which is a unique ecological niche for rhizobial nitrogen fixation. Rhizobial infection has many similarities with pathogenic infection and induction of defence responses accompanies both interactions, but defence responses are induced to a lesser extent during rhizobial infection. However, strong defence responses may result from incompatible interactions between legumes and rhizobia due to a mutation in either macro- or microsymbiont. The aim of this research was to analyse different plant defence reactions in response to Rhizobium infection for several pea (Pisum sativum) mutants that result in ineffective symbiosis. Pea mutants were examined by histochemical and immunocytochemical analyses, light, fluorescence and transmission electron microscopy and quantitative real-time PCR gene expression analysis. It was observed that mutations in pea symbiotic genes sym33 (PsIPD3/PsCYCLOPS encoding a transcriptional factor) and sym40 (PsEFD encoding a putative negative regulator of the cytokinin response) led to suberin depositions in ineffective nodules, and in the sym42 there were callose depositions in infection thread (IT) and host cell walls. The increase in deposition of unesterified pectin in IT walls was observed for mutants in the sym33 and sym42; for mutant in the sym42, unesterified pectin was also found around degrading bacteroids. In mutants in the genes sym33 and sym40, an increase in the expression level of a gene encoding peroxidase was observed. In the genes sym40 and sym42, an increase in the expression levels of genes encoding a marker of hypersensitive reaction and PR10 protein was demonstrated. Thus, a range of plant defence responses like suberisation, callose and unesterified pectin deposition as well as activation of defence genes can be triggered by different pea single mutations that cause perception of an otherwise beneficial strain of Rhizobium as a pathogen.
All-Russia Research Institute for Agricultural Microbiology, Podbelsky chaussee 3, Saint-Petersburg, Pushkin 8, 196608, Russia.
Kira A
KA
Ivanova
All-Russia Research Institute for Agricultural Microbiology, Podbelsky chaussee 3, Saint-Petersburg, Pushkin 8, 196608, Russia.
Anna V
AV
Tsyganova
John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, UK.
Nicholas J
NJ
Brewin
All-Russia Research Institute for Agricultural Microbiology, Podbelsky chaussee 3, Saint-Petersburg, Pushkin 8, 196608, Russia.|Saint-Petersburg State University, Universitetskaya embankment 7-9, Saint-Petersburg, 199034, Russia.
Igor A
IA
Tikhonovich
All-Russia Research Institute for Agricultural Microbiology, Podbelsky chaussee 3, Saint-Petersburg, Pushkin 8, 196608, Russia. tsyganov@arriam.spb.ru.
Viktor E
VE
Tsyganov
D018506:Gene Expression Regulation, Plant; D005838:Genotype; D005936:Glucans / Q000378:metabolism; D007150:Immunohistochemistry; D008055:Lipids; D046529:Microscopy, Electron, Transmission; D008856:Microscopy, Fluorescence; D009154:Mutation; D009586:Nitrogen Fixation; D018532:Pisum sativum / Q000235:genetics / Q000378:metabolism / Q000382:microbiology* / Q000648:ultrastructure; D010368:Pectins / Q000378:metabolism; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism / Q000382:microbiology* / Q000648:ultrastructure; D060888:Real-Time Polymerase Chain Reaction; D016961:Rhizobium leguminosarum / Q000502:physiology*; D053204:Root Nodules, Plant / Q000235:genetics / Q000378:metabolism / Q000382:microbiology* / Q000648:ultrastructure; D012988:Soil Microbiology; D013559:Symbiosis / Q000235:genetics*; D013997:Time Factors; D014157:Transcription Factors / Q000235:genetics*
D005936:Glucans; D008055:Lipids; D010940:Plant Proteins; D014157:Transcription Factors; C065875:suberin; D010368:Pectins; C048306:callose
Callose; Defence response; Pectin; Pisum sativum; Suberin; Symbiotic nodule