Regulation and symbiotic significance of nodulation outer proteins secretion in Sinorhizobium fredii HH103.
In this work we show that the Sinorhizobium fredii HH103 ttsI gene is essential for the expression of the tts genes and secretion of nodulation outer proteins (Nops). Moreover, we demonstrate for the first time, to our knowledge, that the nod box preceding ttsI is necessary for Nops secretion. TtsI is responsible for the transcriptional activation of nopX, nopA, rhcJ and rhcQ. We confirm that the S. fredii HH103 ttsI gene is activated by NodD1 and repressed by NolR. In contrast, NodD2 is not involved in the regulation of ttsI expression. Despite the dependence of expression of both ttsI and nodA on NodD1 and flavonoids, clear differences in the capacity of some flavonoids to activate these genes were found. The expression of the ttsI and nodA genes was also sensitive to differences in the pH of the media. Secretion of Nops in the ttsI mutant could not be complemented with a DNA fragment containing the ttsI gene and its nod box, but it was restored when a plasmid harbouring the ttsI, rhcC2 and y4xK genes was transferred to the mutant strain. The symbiotic effect of Nops secretion was host-dependent but independent of the type of nodule formed by the host legume. Nops are beneficial in the symbiosis with Glycine max and Glycyrrhiza uralensis, and detrimental in the case of the tropical legume Erythrina variegata.
Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain.
Francisco Javier
FJ
López-Baena
Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain.
José María
JM
Vinardell
Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain.
Francisco
F
Pérez-Montaño
Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain.
Juan Carlos
JC
Crespo-Rivas
Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain.
Ramón A
RA
Bellogín
Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain.
Ma Del Rosario
MDR
Espuny
Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain.
Francisco Javier
FJ
Ollero
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D007887:Fabaceae / Q000382:microbiology; D005419:Flavonoids / Q000494:pharmacology; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D020868:Gene Silencing; D005798:Genes, Bacterial / Q000235:genetics; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D042181:Sinorhizobium fredii / Q000235:genetics / Q000378:metabolism*; D013559:Symbiosis / Q000235:genetics
D001426:Bacterial Proteins; D005419:Flavonoids