Feedback regulation of the Bradyrhizobium japonicum nodulation genes

Loh, JT Stacey, G

Jt. Loh et G. Stacey, Feedback regulation of the Bradyrhizobium japonicum nodulation genes, MOL MICROB, 41(6), 2001, pp. 1357-1364

55

INGLESE

Article

Microbiology

MOLECULAR MICROBIOLOGY

0950-382X → ACNP

41

6

2001

1357 - 1364

ISI

0950-382X(200109)41:6<1357:FROTBJ>2.0.ZU;2-B

Lipochitin Nod signals are produced by rhizobia and are required for the es tablishment of a nitrogen-fixing symbiosis with a legume host. The nodulati on genes encode products required for the synthesis of this signal and are induced in response to plant-produced flavonoid compounds. The addition of chitin and lipochitin oligomers to Bradyrhizobium japonicum cultures result ed in a significant reduction in the expression of a nod-lacZ fusion. Intra cellular expression of NodC, encoding a chitin synthase, also reduced nod g ene expression. In contrast, expression of the ChiB chitinase increased nod gene expression. The chain length of the oligosaccharide was important in feedback regulation, with chitotetraose molecules the best modulators of no d gene expression. Feedback regulation is mediated by the induction of noIA by chitin, resulting in elevated levels of the repressor protein, NodD2.