A novel alpha-amylase gene is transiently upregulated during low temperature exposure in apple fruit.
An alpha-amylase gene product was isolated from apple fruit by reverse-transcriptase PCR using redundant primers, followed by 5' and 3' RACE. The gene is a member of a small gene family. It encodes a putative 46.9 kDa protein that is most similar to an alpha-amylase gene from potato (GenBank accession M79328). In apple fruit this new gene was expressed at low levels, as detected by reverse-transcriptase PCR, in a number of plant tissues and during fruit development. Highest levels of mRNA for this transcript were observed 3 to 9 days after placing apple fruit at 0.5 degrees C. Phylogenetic analysis of amino acid sequence places the potato and apple proteins as a distinct and separate new subgroup within the plant alpha-amylases, which appears to have diverged prior to the split between monocotyledonous and dicotyledonous plants. These two divergent alpha-amylases lack the standard signal peptide structures found in all other plant alpha-amylases, and have sequence differences within the B-domain and C-domain. However, comparisons with structures of known starch hydrolases suggest that these differences are unlikely to affect the enzymatic alpha-1,4-amylase function of the protein. This is the first report of upregulation of a dicotyledonous alpha-amylase in response to low temperature, and confirms the presence of a new family of alpha-amylases in plants.
Wegrzyn
T
T
The Horticulture and Food Research Institute of New Zealand, Mt. Albert Research Centre, Auckland.
Reilly
K
K
Cipriani
G
G
Murphy
P
P
Newcomb
R
R
Gardner
R
R
MacRae
E
E
D000595:Amino Acid Sequence; D001483:Base Sequence; D003080:Cold Temperature; D018076:DNA, Complementary; D005638:Fruit / Q000201:enzymology*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010802:Phylogeny; D011487:Protein Conformation; D012333:RNA, Messenger / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D015854:Up-Regulation; D000516:alpha-Amylases / Q000235:genetics*
D018076:DNA, Complementary; D012333:RNA, Messenger; D000516:alpha-Amylases