Soybean Seed Lectin Prevents the Accumulation of S-Adenosyl Methionine Synthetase And the S1 30S Ribosomal Protein in Bradyrhizobium japonicum Under C and N Starvation

Abstract

Soybean lectin (SBL) participates in the recognitionbetween Bradyrhizobium japonicum and soybeanalthough its role remains unknown. To search for changesin the proteome in response to SBL, B. japonicum USDA110 was incubated for 12 h in a C- and N-free mediumwith or without SBL (10 lg ml -1), and the soluble proteinprofiles were compared. Two polypeptides, S-adenosylmethioninesynthetase (MetK) and the 30S ribosomalprotein S1 (RpsA), were found only in the fractions fromrhizobia incubated without SBL. Transcript levels of metKand rpsA were not correlated with polypeptide levels,indicating that there was regulation at translation. In supportof this proposal, the 50 translation initiation-region ofrpsA mRNA contained folding elements as those involvedin regulation of its translation in other species. Disappearanceof MetK and RpsA from the soluble proteinfractions of SBL-treated rhizobia suggests that SBL mighthave attenuated the nutritional stress response ofB. japonicum.