Cloning and characterization of NADPH-dependent double-bond reductases from Alnus sieboldiana that recognize linear diarylheptanoids as substrates.

Diarylheptanoids are secondary metabolites of plants that comprise a C-C-C scaffold. They can be broadly classified into linear-type and cyclic-type diarylheptanoids based on their chemical structures. Actinorhizal trees, such as Casuarina, Alnus, and Myrica, which form nodule symbiosis with actinomycetes Frankia, produce cyclic diarylheptanoids (CDHs); in Alnus sieboldiana Matsum.

Cyclic diarylheptanoids as potential signal compounds during actinorhizal symbiosis between Alnus sieboldiana and Frankia.

The nitrogen-fixing actinomycete Frankia coexists with actinorhizal plants via nodules and supplies nitrogen compounds to the plants. Although communication has been suggested to exist through chemical substances in this nodule symbiosis, the details underlying this mechanism remain elusive. The biphenyl-type diarylheptanoids (BP-CDHs), alnusonol, and alnusdione, previously isolated from the actinorhizal plant A.