Biomedical subjects

J Mitchell McGrath

Publications and source records attributed to J Mitchell McGrath.

3 recordsLinked to original sources

PubMed2005

Sugarbeet sucrose synthase genes differ in organ-specific and developmental expression.

A full-length sucrose synthase (SBSS2) cDNA clone was isolated from sugarbeet. Comparison of its composition and organ-specific and developmental expression with a previously isolated sugarbeet sucrose synthase gene (SBSS1) revealed distinct differences between the two genes. The two genes share 80% similarity in deduced amino acid sequence but belong to different sucrose synthase subclasses based on phylogenic analysis. Both sucrose synthases were highly expressed in roots, and had low levels of expression in leaf tissue. Transcript abundance of SBSS2, relative to SBSS1, was greater in young vegetative and floral tissues, and reduced in mature vegetative tissues. The organ-specific and developmental expression of SBSS1 and SBSS2 proteins was similar to SBSS1 and SBSS2 transcript levels, although developmental changes in protein abundance lagged transcriptional changes by many weeks. The similarities and differences in transcript and protein abundance suggest that both transcriptional and post-transcriptional regulatory mechanisms are likely to contribute to sucrose synthase expression in sugarbeet.

Base Sequence↗

PubMed2004

Fluorometric sucrose evaluation for sugar beet.

Sucrose is the economic product from sugar beet. Disease resistance is often available in low-sucrose genotypes and, prior to the deployment of such novel genes as available into the cultivated spectrum, selection for increased sucrose content is required during introgression. The objective of this work was to evaluate a relatively rapid and inexpensive enzymatic-fluorometric microtiter plate assay for sucrose quantification in sugar beet root dry matter, both for progeny testing in the greenhouse and for evaluation of field-grown mother roots. As determined using HPLC, sucrose content in diverse populations of sugar and table beet assayed over various developmental stages ranged from 0.213 to 2.416 mmol g(-1) of dry matter, and these values were used as references for both refractometry and enzymatic-fluorometric assay. As expected, refractometric analysis generally overestimated sucrose content. Enzymatic-fluorometric analyses were reasonably well correlated with HPLC results for young greenhouse-grown root tissues (R2 = 0.976), and less so with older field-grown roots (R2 = 0.605), for unknown reasons. Enzymatic-fluorometric assays may be best deployed for progeny testing of young seedlings.

Beta vulgaris↗

PubMed2003

Cultivar-specific seedling vigor and expression of a putative oxalate oxidase germin-like protein in sugar beet (Beta vulgaris L.).

For genetic screening and breeding purposes, an in vitro germination system that reflects relative field emergence potential was used to screen for germination-enhancing and stress-induced genes from germinating seedlings from two varieties of sugar beet. Three full-length germin-like protein (GLP) gene classes were recovered from stress-germinated seedlings of a superior emerging variety. GLP gene expression, oxalate oxidase protein activity, the H(2)O(2) content of stressed seedlings, but not catalase activity, were induced by stress germination conditions (e.g. excess water, NaCl, mannitol, or oxalate) in a good emerging hybrid and were not induced in a poor emerging variety. Only one of the three germin-like protein genes ( BvGer165) was differentially regulated, and was induced only in the good emerger. Hydrogen peroxide promoted germination and partially compensated solute-depressed germination percentages. Unlike other solute recovery by hydrogen peroxide regimes, recovery in oxalic acid plus H(2)O(2) was cultivar-independent. A block in oxalate metabolism is postulated to contribute to lower germination under stress in the lower emerging variety. Selection for stress-induced germin expression, or for down-stream targets, presents the first direct target to enable breeding for improved field emergence of sugar beet.

Beta vulgaris↗