An attempt to isolate nodule-specific cDNA clones from Alnus incana.

Abstract

Here we report on the attempt to isolate nodule-specific cDNA clones from a cDNA library that was derived from an actinorhizal species, Alnus incana, nodule poly A+ enriched RNA. mRNA corresponding to these cDNA clones could be detected in RNA isolated from the actinorhizal nodule but, could not be detected in RNA isolated from the root. The pattern of expression of four genes corresponding to the cDNA clones was investigated at various time points following infection. It appears the nodulin clones could be divided into two categories of expression; one showing a maximal expression prior to the onset of nitrogen fixation, and the other expressing a maximal level after the onset of nitrogen fixation. Sequence characterization of these clones eventually revealed that the cDNA clones were ribosomal in nature of both plant and bacterial origin. However, further analysis revealed that one cDNA clone of bacterial origin had a unique 105 bp region. PCR analysis suggests that it may be possible to survey various bacterial species for the presence or absence of this insert in order to classify and investigate the evolution of 23S rRNA within this region of the gene. (Abstract shortened by UMI.)