Abstract
We have previously reported that Klebsormidium flaccidum, a green alga (Charophyceae), which lives in cold regions and belongs to sister group of land plants, increases freezing tolerance during cold acclimation. The increase is associated with increases in the content of sucrose and γ-aminobutyric acid (GABA), both of which are closely associated with in freezing tolerance of land plants. We here isolated genes encoding key enzymes of biosynthetic pathways of sucrose (sucrose phosphate phosphatase, SPP) and GABA (glutamate decarboxylase, GAD) in K. flaccidum by PCR amplification using degenerate primers constructed with information on conserved amino acid sequence segments of SPPs and GADs of land plants. The deduced amino acid sequences of isolated cDNA fragments of KfSPP and KfGAD showed high similarities to those of SPPs and GADs of land plants. KfSPP and KfGAD may be associated with the accumulation of sucrose and GABA during cold acclimation in K. flaccidum.
