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ARS Home » Midwest Area » Urbana, Illinois » Global Change and Photosynthesis Research » Research » Publications at this Location » Publication #258157
Title: Comparison of a novel tomato sucrose synthase, SISUS4, with previously described SISUS isoforms reveals distinct sequence features and differential expression patterns in association with stem maturation

Author
item GOREN, SHLOMO - Volcani Center (ARO)
item Huber, Steven
item GRANOT, DAVID - Volcani Center (ARO)

Submitted to: Planta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/5/2011
Publication Date: 5/1/2011
Citation: Goren, S., Huber, S.C., Granot, D. 2011. Comparison of a novel tomato sucrose synthase, SISUS4, with previously described SISUS isoforms reveals distinct sequence features and differential expression patterns in association with stem maturation. Planta. 233:1011-1023.

Interpretive Summary: Sucrose synthase is an important enzyme of sucrose metabolism in growing plant organs, including stems, roots and seeds, and channels carbon from sucrose into various metabolic and biosynthetic pathways. The activity of sucrose synthase in a growing organ is thought to be a determinant of growth. In all species studied to date, sucrose synthase is encoded by a small gene family; however, the biological significance of the encoded protein isoforms is not clear in most cases. In the present study, we characterized the sucrose synthase isoforms using tomato as a model system. First, we report the identification of a novel tomato sucrose synthase isoform, designated SlSUS4. At the DNA level, the new gene is very similar in sequence and genomic structure to the other two sucrose synthase genes in tomato (SlSUS1 and SlSUS3), suggesting a common evolutionary origin for all three genes. However, two of the genes show opposing expression gradients along the developmental axis of the tomato stem, suggesting a specific role in vascular bundle development. These results strengthen the notion that sucrose synthase isoforms may play specialized roles in development, and because of the importance of vascular development in plant architecture may provide new approaches to improve crop productivity in the future.

Technical Abstract: Sucrose synthase (SuSy) plays many roles in sugar metabolism, including low oxygen and low-ATP respiration and the synthesis of cellulose. In tomato (Solanum lycopersicum), as in many plants, SuSy is encoded by genes at several independent loci. Here, we report the isolation of a novel tomato SuSy (SlSUS) isoform, SlSUS4, that is homologous to potato SuSy isoform 1 (StSUS1) and also shows greater homology to SuSy isoforms of other plants than to the other tomato SuSy isoforms. All three tomato isoforms are very similar in genomic structure and sequence, yet each is located on a separate chromosome. Real-time expression analysis of the three distinct isoforms revealed widely varying patterns of expression, in terms of both tissue specificity and overall magnitude of expression. Analysis of SlSUS expression along the tomato stem revealed opposing expression gradients for two of the SlSUS isoforms, in apparent correlation with xylem maturation. Western blot analysis of SlSUS protein showed an increasing SISUS expression gradient along the developmental axis of the tomato stem, with the protein concentrated mainly in the xylem tissue of the stem. These expression patterns indicate that each isoform may play a discrete role in the development of tomato plants, most notably in the development of vascular tissue in the stem.