Isolation of two distinct cold-inducible cDNAs encoding plant uncoupling proteins from the spadix of skunk cabbage (Symplocarpus foetidus)

To know the involvement of mitochondrial uncoupling protein (UCP) in thermogenesis in plants, cDNA cloning of UCP-like gene was performed using cDNA library prepared from the spadix of skunk cabbage (Symplocarpus foetidus). Two novel cDNAs (SfUCPa and SfUCPb) encoding uncoupling proteins were isolated. The SfUCPa cDNA contained an open reading frame of 303 amino acids (predicted molecular weight 32.6 kDa) while the SfUCPb cDNA encoded 268 amino acids (predicted molecular weight 29.0 kDa). While the SfUCPA protein had six transmembrane domains and three mitochondrial energy-transfer protein signatures that are characteristic of all known UCPs, SfUCPB lacks the fifth transmembrane domain and the third energy-transfer protein signature, suggesting an altered topology in the inner membrane of the mitochondria. The expression of SfUCPa and SJUCPb mRNAs was detected only in the spadix but not in the leaf. Further, the extents of the expression of SfUCPa and SJUCPb mRNAs were induced by low-temperature treatment. These data suggest that SfUCPA and SfUCPB may have an important role in thermogenesis in the spadix; of skunk cabbage. (C) 1999 Published by Elsevier Science Ireland Ltd. All rights reserved.