Pea (Pisum sativum) genes involved in symbiosis with nitrogen-fixing bacteria.1.Analysis of the expression of the early nodulin gene ENOD12 using the polymerase chain-reaction

The polymerase chain reaction (PCR) was used to detect the transcription products of the early nodulin gene in the pea. Single-stranded DNA copies were prepared using a primer corresponding to the terminal part of a previously sequenced cDNA clone and a total RNA isolate. The presence of amplification products was detected using Southern hybridization. Expression of the ENOD12 gene was found to occur at the earliest developmental stages of the symbiosis between the pea and nitrogenfixing bacteria, and occurred in root hair cell. Transcription activation required sufficient levels of activity of a limited number of symbiotic bacterial genes, namely nodDABC and nodE. Expression of ENOD12 was inducible by a soluble component excreted into the medium by activated bacteria, and by inhibitors of soluble hormone (auxins) transport. The ENOD12 gene was shown to lack introns