Open AccessThe rhizobial adhesion protein RapA1 is involved in adsorption of rhizobia to plant roots but not in nodulation
Author(s) -
Mongiardini Elías J.,
Ausmees Nora,
PérezGiménez Julieta,
Julia Althabegoiti María,
Ignacio Quelas Juan,
LópezGarcía Silvina L.,
Lodeiro Aníbal R.
Publication year - 2008
Publication title -
fems microbiology ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.377
H-Index - 155
eISSN - 1574-6941
pISSN - 0168-6496
DOI - 10.1111/j.1574-6941.2008.00467.x
Subject(s) - rhizobium leguminosarum , biology , rhizobia , rhizobium , rhizosphere , red clover , rhizobiaceae , root hair , plasmid , microbiology and biotechnology , adsorption , symbiosis , inoculation , botany , gene , bacteria , biochemistry , horticulture , chemistry , genetics , organic chemistry
The effect of the rhizobium adhesion protein RapA1 on Rhizobium leguminosarum bv. trifolii adsorption to Trifolium pratense (red clover) roots was investigated. We altered RapA1 production by cloning its encoding gene under the p lac promoter into the stable vector pHC60. After introducing this plasmid in R. leguminosarum bv. trifolii , three to four times more RapA1 was produced, and two to five times higher adsorption to red clover roots was obtained, as compared with results for the empty vector. Enhanced adsorption was also observed on soybean and alfalfa roots, not related to R. leguminosarum cross inoculation groups. Although the presence of 1 mM Ca 2+ during rhizobial growth enhanced adsorption, it was unrelated to RapA1 level. Similar effects were obtained when the same plasmid was introduced in Rhizobium etli for its adsorption to bean roots. Although root colonization by the RapA1‐overproducing strain was also higher, nodulation was not enhanced. In addition, in vitro biofilm formation was similar to the wild‐type both on polar and on hydrophobic surfaces. These results suggest that RapA1 receptors are present in root but not on inert surfaces, and that the function of this protein is related to rhizosphere colonization.