A symbiotic plant peroxidase involved in bacterial invasion of the tropical legume Sesbania rostrata.
Aquatic nodulation on the tropical legume Sesbania rostrata occurs at lateral root bases via intercellular crack-entry invasion. A gene was identified (Srprx1) that is transiently up-regulated during the nodulation process and codes for a functional class III plant peroxidase. The expression strictly depended on bacterial nodulation factors (NFs) and could be modulated by hydrogen peroxide, a downstream signal for crack-entry invasion. Expression was not induced after wounding or pathogen attack, indicating that the peroxidase is a symbiosis-specific isoform. In situ hybridization showed Srprx1 transcripts around bacterial infection pockets and infection threads until they reached the central tissue of the nodule. A root nodule extensin (SrRNE1) colocalized with Srprx1 both in time and space and had the same NF requirement, suggesting a function in a similar process. Finally, in mixed inoculation nodules that were invaded by NF-deficient bacteria and differed in infection thread progression, infection-associated peroxidase transcripts were not observed. Lack of Srprx1 gene expression could be one of the causes for the aberrant structure of the infection threads.
Den Herder
Jeroen
J
Department of Plant Systems Biology, Flanders Institute for Biotechnology, and Department of Molecular Genetics, Ghent University, B-9052 Ghent, Belgium.
Lievens
Sam
S
Rombauts
Stephane
S
Holsters
Marcelle
M
Goormachtig
Sofie
S
D000595:Amino Acid Sequence; D020599:Azorhizobium caulinodans / Q000502:physiology*; D001426:Bacterial Proteins / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D006861:Hydrogen Peroxide / Q000378:metabolism; D017403:In Situ Hybridization; D008969:Molecular Sequence Data; D010544:Peroxidases / Q000378:metabolism*; D010935:Plant Diseases; D053204:Root Nodules, Plant / Q000201:enzymology* / Q000382:microbiology; D049931:Sesbania / Q000201:enzymology* / Q000382:microbiology; D013559:Symbiosis / Q000502:physiology*; D015854:Up-Regulation
D001426:Bacterial Proteins; D006861:Hydrogen Peroxide; D010544:Peroxidases