title: A 2.5-kb insert eliminates acid soluble invertase isozyme II transcript in carrot (Daucus carota L.) roots, causing high sucrose accumulation.
abstract: The predominant storage carbohydrates of mature carrot (Daucus carota L.) storage roots typically are the free sugars glucose and fructose. This trait is conditioned by the Rs allele. A naturally occurring recessive mutation, rs/rs, conditions a shift from these reducing sugars to sucrose. RT-PCR and sequencing revealed a unique 2.5 kb insert in the first and largest intron near the 5' end of the acid soluble invertase isozyme II gene of rs/rs carrots. This insert was not totally spliced out during mRNA processing. While the wild-type acid-soluble invertase isozyme II transcript (ca. 2 kb) was detected in Rs/Rs roots and leaves, none was observed in rs/rs roots throughout development. RT-PCR of rs/rs leaves revealed two novel transcripts (2.7 kb and 3.2 kb). A comparison of enzyme activity between the near-isogenic Rs/Rs and rs/rs carrot lines revealed very low acid-soluble invertase activity in rs/rs roots whereas neutral invertase, sucrose synthase and sucrose phosphate synthase levels were comparable. Those results and linkage analysis indicate that Rs is a candidate locus for carrot vacuolar acid-soluble invertase isozyme II. Although the 2.5 kb insert does not occur in the Rs wild-type acid-soluble invertase isozyme II allele, it does occur elsewhere in the genome of Rs/Rs plants.
authors.affiliation: USDA-ARS Vegetable Research Crops Unit, Department of Horticulture, University of Wisconsin-Madison, 1575 Leiden Drive, Madison, WI 53706, USA.
authors.forename: Yuan-Yeu
authors.initials: YY
authors.lastname: Yau
authors.forename: Philipp W
authors.initials: PW
authors.lastname: Simon
mesh_terms: D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D018744:DNA, Plant / Q000737:chemistry / Q000235:genetics; D018552:Daucus carota / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D007527:Isoenzymes / Q000235:genetics; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D018515:Plant Leaves / Q000201:enzymology / Q000235:genetics; D018517:Plant Roots / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D012995:Solubility; D013395:Sucrose / Q000378:metabolism*; D013997:Time Factors; D014158:Transcription, Genetic; D043324:beta-Fructofuranosidase / Q000235:genetics*
chemical_list: D018076:DNA, Complementary; D018744:DNA, Plant; D007527:Isoenzymes; D018749:RNA, Plant; D013395:Sucrose; D043324:beta-Fructofuranosidase