The gene encoding the PSST subunit of respiratory chain complex I is present in more than one copy in yellow lupine.

Three copies of the PSST gene were identified in the lupine genomic root library, however, only two transcripts were found in the lupine root cDNA library. The transcript of the third PSST gene was identified in RNA from lupine flowers. The genes are 92% identical in the coding region, while the 5' parts of the reading frames specifying the N-terminal presequences for mitochondrial import show about 87% sequence identity.