The nodD1 Gene of Sinorhizobium fredii HH103 Restores Nodulation Capacity on Bean in a Rhizobium tropici CIAT 899 nodD1 / nodD2 Mutant, but the Secondary Symbiotic Regulators nolR , nodD2 or syrM Prevent HH103 to Nodulate with This Legume

• Published in: Microorganisms (Basel) Vol. 10; no. 1; p. 139
• Main Authors: Fuentes-Romero, Francisco, Navarro-Gómez, Pilar, Ayala-García, Paula, Moyano-Bravo, Isamar, López-Baena, Francisco-Javier, Pérez-Montaño, Francisco, Ollero-Márquez, Francisco-Javier, Acosta-Jurado, Sebastián, Vinardell, José-María
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 10-01-2022; MDPI
• Subjects: Acetylene; Acetylene reduction; Bacterial infections; Beans; Biological activity; Flavonoids; Gene expression; Host plants; Inactivation; Legumes; Mutants; Mutation; Nitrogenase; Nod factors; nodD1; Nodulation; Nodules; Phaseolus vulgaris; Plasmids; Proteins; rhizobia–legume symbiosis; Rhizobium tropici; Rhizobium tropici CIAT 899; Seeds; Sinorhizobium fredii; Sinorhizobium fredii HH103; Soybeans; Symbiosis; Symbiotic behavior; ttsI; Rhizobium tropici CIAT 899; nodD1; nodD2; Sinorhizobium fredii HH103; nolR; Nod factors; Phaseolus vulgaris; syrM; rhizobia–legume symbiosis
• ISSN: 2076-2607; 2076-2607
• DOI: 10.3390/microorganisms10010139

Rhizobial NodD proteins and appropriate flavonoids induce rhizobial nodulation gene expression. In this study, we show that the
gene of
HH103, but not the
gene, can restore the nodulation capacity of a double
/
mutant of
CIAT 899 in bean plants (
).
HH103 only induces pseudonodules in beans. We have also studied whether the mutation of different symbiotic regulatory genes may affect the symbiotic interaction of HH103 with beans:
(the positive regulator of the symbiotic type 3 protein secretion system), and
,
and
(all of them controlling the level of Nod factor production). Inactivation of either
,
or
, but not that of
, affected positively the symbiotic behavior of HH103 with beans, leading to the formation of colonized nodules. Acetylene reduction assays showed certain levels of nitrogenase activity that were higher in the case of the
and
mutants. Similar results have been previously obtained by our group with the model legume
. Hence, the results obtained in the present work confirm that repression of Nod factor production, provided by either NodD2, NolR or SyrM, prevents HH103 to effectively nodulate several putative host plants.