Study on the major diazotrophs associated with Norway spruce (Picea abies L. Karst) roots

In this study major diazotrophs associated with medium-coarse roots of Norway spruce (Picea abies L. Karst) in a typical northern hemisphere temperate forest were investigated by applying RNA-based and protein-based methods. NifH transcripts identical to the partial nifH sequence of the grass endophyte Azoarcus sp. BH72 were repeatedly detected in RNA extracts from spruce sampled in different months using broad-range nifH primer sets with both single-stage and nested RT-PCR approaches. The nifH expression level was evaluated with real-time reverse transcriptase-polymerase chain reaction (RT-PCR) using Azoarcus sp. BH72-specific and universal nifH primers. NifH expression profiles showed that the nifH transcript levels changed with season and were highest in summer.