An apigenin-induced decrease in K-antigen production by Sinorhizobium sp. NGR234 is y4gM- and nodD1-dependent.

Area of Science:

• Microbiology
• Plant-microbe interactions
• Bacterial polysaccharide synthesis

Background:

• Sinorhizobium sp. NGR234 produces abundant capsular polysaccharides (K antigens).
• Apigenin, a nod gene inducer, reduces K-antigen production in cultured cells.
• This modulation is potentially linked to bacteroid differentiation.

Purpose of the Study:

• To investigate the effect of apigenin on K-antigen production in Sinorhizobium sp. NGR234.
• To determine the role of bacteroid differentiation in K-antigen reduction.
• To identify genetic factors involved in flavonoid-induced K-antigen decrease.

Main Methods:

• Culturing Sinorhizobium sp. NGR234 with and without apigenin.
• Extracting polysaccharides from cultured cells and bacteroids.
• Analyzing polysaccharide composition from wild-type and nodulation mutants.
• Recovering bacteroids from Vigna unguiculata root nodules.

Main Results:

• Apigenin significantly reduced K-antigen production in cultured Sinorhizobium sp. NGR234.
• Bacteroid extracts from Vigna unguiculata nodules were nearly devoid of K-antigen.
• The apigenin-induced decrease in K-antigen production was dependent on y4gM and nodD1 genes.

Conclusions:

• Flavonoid-induced K-antigen reduction in Sinorhizobium sp. NGR234 is linked to bacteroid differentiation.
• The genes y4gM and nodD1 are crucial for this flavonoid-inducible decrease in K-antigen production.