Development- and organ-specific expression of the genes for sucrose synthase and three isoenzymes of acid β-fructofuranosidase in carrot

Abstract

Abstract. The steady-state levels of transcripts for cellwall 13-fructofuranosidase (cwl3F), for isoenzymes I and II of soluble acid 13-fructofuranosidase (sI, slI), and for sucrose synthase (ss) were determined in the sink and source organs of developing carrot (Daucus carota L.) plants. The expression patterns of the four genes clearly differed. The expression of the gene for cwl3F was development-specific but not organ-specific; high transcript levels were only found in plants with primary roots, with about equal amounts in leaf lamina, petioles and roots. The genes for sI and slI were mainly expressed in roots, sI predominating in primary roots and slI in developing tap roots. Transcripts for ss were found at a low level in all developing plant organs and were markedly up-regulated during the development of young leaves and during the transition of primary roots to tap roots. Developing tap roots contained only transcripts for slI and for ss. Marked alterations in the expression of these two genes after manipulation of the source/sink balance of these plants indicates their importance in sucrose partitioning. We suggest that ss regulates sucrose utilization in developing tap roots, whereas slI located in the vacuole controis sucrose storage and sugar composition.

Invertases. Primary Structures, Functions, and Roles in Plant Development and Sucrose Partitioning

“…Comparison of their 5Ј upstream regions showed no common sequence elements, suggesting independent modes of regulation. Analysis of isoformspecific steady-state transcript levels confirmed this finding and showed markedly different organ-and development-stage-specific expression patterns (Sturm et al, 1995). Similar results were obtained in a study of the expression of genes for one vacuolar and four cell wall invertase isoforms from tomato (Godt and Roitsch, 1997).…”

“…Genes for acid invertases have been isolated from tomato (Elliott et al, 1993), Arabidopsis (for summary, see Tymowska-Lalanne and Kreis, 1998), maize (Xu et al, 1995), and carrot (Ramloch-Lorenz et al, 1993;Lorenz et al, 1995;Sturm, 1996). Their structures are fairly similar and contain six to eight exons (Tymowska-Lalanne and Kreis, 1998).…”

Sucrose protects cell wall invertase but not vacuolar invertase against proteinaceous inhibitors

“…Developmental control of gene expression has been observed for different isoforms of VI and CWI [9,10]. Furthermore, CWI has been implicated in the wound response and may be induced by pathogen attack [10].…”

The trans‐tissue pathway and chemical fate of 14C photoassimilate in carrot taproot

“…However, the absence of cell wall invertase in carrot taproot (Sturm et al, 1995) and the absence of sucrose cleavage before uptake (Daie, 1984) have been shown. Accumulation of insoluble "%C began in the cambial region 4 h after "%CO # feeding.…”

“…Movement of the assimilate from the active sieve tubes to the place of their consumption or storage (radial transport) might involve apoplastic and\or symplastic unloading, passage to the storage cells and uptake by those cells (Sturm et al, 1995 ;Hole, 1996 ;Patrick, 1997). The uptake of "%C-sugars from the apoplast was shown for slices of both phloem (Daie, 1984 ;Hole & Dearman, 1994) and xylem (Hole, 1996) parenchyma of the carrot taproot.…”