ARS | Publication request: LACK OF ACID SOLUBLE INVERTASE ISOZYME II TRANSCRIPT IS ASSOCIATED WITH HIGH SUCROSE ACCUMULATION IN A NATURALLY OCCURRING INVERTASE MUTANT OF CARROT (DAUCUS CAROTA L.)

Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Abstract Only
Publication Acceptance Date: January 8, 2000
Publication Date: N/A

Technical Abstract: Invertase is an important enzyme controlling sucrose balance in most plants. In carrot (Daucus carota L.) three major isoforms occur: acid soluble invertase isozyme I (ASI-I), acid soluble invertase isozyme II (ASI-II), and insoluble cell wall invertase (CWI). The Rs locus conditions sugar accumulation in the storage roots that plants accumulate glucose and fructose while rs/rs plants predominantly accumulate sucrose. Little is known of this locus. With near-isogenic Rs/Rs and rs/rs lines of carrot inbred line B4367, referred to as B4367Rs and B4367rs respectively, we identified an acid invertase isozyme II mutation. We compare the differential expression of ASI-I, ASI-II and CWI mRNA in B4367Rs and B4367rs using reverse transcription polymerase chain reaction (RT-PCR). ASI-I and CWI mRNA patterns are similar in B4367Rs and B4367rs throughout development, and B4367Rs expressed ASI-II (2.0 Kb), but for B4367rs roots, no ASI-II mRNA could be detected throughout development (week 1 to week 20 post-germination) and at mature state (week 60). In B4367rs leaves, approximately 2.7 Kb and 3.2 Kb, were observed with RT-PCR. RCR amplification of ASI-II from genomic DNA of B4367Rs and B4367rs also revealed two different product sizes,4 Kb and 6 Kb respectively. This is the first report associating high sucrose accumulation with a lack of ASI-II transcript. The characteristics of distinct genomic PCR amplification products distinguishing Rsl- and rs/rs carrots make ASI-II a convenient marker to distinguish high sucrose carrot roots from low sucrose carrot roots in a carrot breeding program.