N-deacetylation of Sinorhizobium meliloti Nod factors increases their stability in the Medicago sativa rhizosphere and decreases their biological activity.
Nod factors excreted by rhizobia are signal molecules that consist of a chitin oligomer backbone linked with a fatty acid at the nonreducing end. Modifications of the Nod factor structures influence their stability in the rhizosphere and their biological activity. To test the function of N-acetyl groups in Nod factors, NodSm-IV(C16:2,S) from Sinorhizobium meliloti was enzymatically N-deacetylated in vitro with purified chitin deacetylase from Colletotrichum lindemuthianum. A family of partially and completely deacetylated derivatives was produced and purified. The most abundant chemical structures identified by mass spectrometry were GlcN(C16:2)-GlcNAc-GlcNH2-GlcNAc(OH)(S), GlcN(C16,2)-GlcNAc-GlcNH2-GlcNH2(OH)(S), and GlcN(C16:2)-GlcNH2-GlcNH2-GlcNH2(OH)(S). In contrast to NodSm-IV(C16:2,S), the purified N-deacetylated derivatives were stable in the rhizosphere of Medicago sativa, indicating that the N-acetyl groups make the carbohydrate moiety of Nod factors accessible for glycosyl hydrolases of the host plant. The N-deacetylated derivatives displayed only a low level of activity in inducing root hair deformation. Furthermore, the N-deacetylated molecules were not able to stimulate Nod factor degradation by M. sativa roots, a response elicited by active Nod factors. These data show that N-acetyl groups of Nod factors are required for biological activity.
Staehelin
C
C
Institut des Sciences Végétales, Centre National de la Recherche Scientifique, Gif-sur-Yvette, France. Chr.Staehelin@unibas.ch
Schultze
M
M
Tokuyasu
K
K
Poinsot
V
V
Promé
J C
JC
Kondorosi
E
E
Kondorosi
A
A
D000581:Amidohydrolases / Q000737:chemistry; D002240:Carbohydrate Sequence; D002851:Chromatography, High Pressure Liquid; D013058:Mass Spectrometry; D000455:Medicago sativa / Q000378:metabolism* / Q000382:microbiology; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D016962:Sinorhizobium meliloti / Q000378:metabolism*; D013559:Symbiosis
C404399:Nod factor NodSm IV; D009844:Oligosaccharides; D000581:Amidohydrolases; C019866:chitin deacetylase