SUGARBEET SUCROSE SYNTHASE GENE EXPRESSION IS ORGAN-SPECIFIC, DEVELOPMENTALLY REGULATED, AND AFFECTED BY ABIOTIC STRESSES.

Authors: Fugate, Karen; Haagenson, Darrin

Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 6/6/2005
Publication Date: 10/31/2005
Citation: Klotz, K.L., Haagenson, D.M. 2005. Sugarbeet sucrose synthase gene expression is organ-specific, developmentally regulated, and affected by abiotic stresses [abstract]. Annual Meeting Abstracts [CD ROM]. Madison, WI ASA-CSSA-SSSA.

Interpretive Summary:

Technical Abstract: Sucrose synthase is the predominant sucrose degrading activity in sugarbeet (Beta vulgaris L.) root and is believed to have roles in carbohydrate partitioning to the root during production and sucrose loss during storage. Two genes, sugarbeet sucrose synthase 1 (SBSS1) and sugarbeet sucrose synthase 2 (SBSS2), contribute to sucrose synthase activity in sugarbeet root. To improve our understanding of sucrose synthase expression and the factors that control it, the organ-specific and developmental expression of these two genes and their responses to environmental factors were determined. SBSS1 and SBSS2 exhibited high transcriptional expression in roots and low transcriptional expression in leaves. In floral tissues, SBSS1 and SBSS2 exhibited low and moderate levels of expression, respectively. In the root, SBSS1 transcripts were evident at all developmental stages, with greatest transcript abundance during mid-season growth. SBSS2 transcript levels were greatest during early root development and were expressed at very low levels during late season growth. SBSS1 and SBSS2 protein levels generally reflected changes in transcript abundance, although changes in protein abundance were greatly delayed from transcriptional changes. Abiotic stresses had different effects on the steady state transcript levels of the two genes. SBSS1 transcript levels increased in response to anoxia and wounding, were unaffected by cold temperature, and reduced in response to harvest. SBSS2 transcript abundance increased in response to cold temperature and wounding and declined in response to harvest and anoxic conditions. Transcriptional changes in expression due to abiotic stresses did not correspond to similar changes in protein levels or enzyme activity. The differences between transcript abundance, protein abundance and enzyme activity suggest that protein stability and posttranscriptional regulation of expression may be important determinants of sucrose synthase activity in sugarbeet root.