Hybrid 'Sinta' papaya exhibits unique ACC synthase 1 cDNA isoforms.
Five ripening-related ACC synthase cDNA isoforms were cloned from 80% ripe papaya cv. 'Sinta' by reverse transcription-PCR using gene-specific primers. Clone 2 had the longest transcript and contained all common exons and three alternative exons. Clones 3 and 4 contained common exons and one alternative exon each, while clone 1, the most common transcript, contained only the common exons. Clone 5 could be due to cloning artifacts and might not be a unique cDNA fragment. Thus, there are only four isoforms of ACC synthase mRNA. Southern blot analysis indicates that all five clones came from only one gene existing as a single copy in the 'Sinta' papaya genome. Multiple sequence alignment indicates that the four isoforms arise from a single gene, possibly through alternative splicing mechanisms. All the putative alternative exons were present at the 5'-end of the gene comprising the N-terminal region of the protein. 'Sinta' ACC synthase cDNAs were of the capacs 1 type and are most closely related to a 1.4 kb capacs 1-type DNA (AJ277160) from Eksotika papaya. No capacs 2-type cDNAs were cloned from 'Sinta' by RT-PCR. This is the first report of possible alternative splicing mechanism in ripening-related ACC synthase genes in hybrid papaya, possibly to modulate or fine-tune gene expression relevant to fruit ripening.
Hidalgo
Marie-Sol P
MS
Institute of Plant Breeding, College of Agriculture, University of the Philippines Los Baños, College, Laguna 4031, Philippines.
Tecson-Mendoza
Evelyn Mae
EM
Laurena
Antonio C
AC
Botella
Jose Ramon
JR
D000595:Amino Acid Sequence; D001483:Base Sequence; D029441:Carica / Q000145:classification / Q000201:enzymology*; D017931:DNA Primers; D018076:DNA, Complementary / Q000235:genetics; D018744:DNA, Plant / Q000737:chemistry / Q000235:genetics*; D007527:Isoenzymes / Q000235:genetics; D008190:Lyases / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D017931:DNA Primers; D018076:DNA, Complementary; D018744:DNA, Plant; D007527:Isoenzymes; D010940:Plant Proteins; D008190:Lyases; C021773:1-aminocyclopropanecarboxylate synthase