Temporal and Spatial Expression Pattern of Sucrose Synthase during Tomato Fruit Development

Abstract

Sucrose synthase is proposed to play an important role in the early stages of tomato fruit (Lycopersicon esculentum Mill.) growth. In this work, the temporal and spatial expression patterns of sucrose synthase during tomato fruit development were investigated. Fruit contained the majority of the sucrose synthase protein and mRNA relative to other organs. Only trace levels of sucrose synthase protein and mRNA were detected in the stem, petiole, and roots. Sucrose synthase mRNA was detected in pistils prior to anthesis, reached peak levels in fruit 5 to 7 d after anthesis (DAA), and was not detectable after 35 DAA. Sucrose synthase protein levels reached a maximum at 20 to 25 DAA and then declined to nondetectable levels after 45 DAA. The lack of coordination between protein and mRNA levels suggests that sucrose synthase expression may be controlled at the levels of both transcription and translation. Sucrose synthase mRNA was differentially localized in the fruit, being most abundant in the mesocarp cells adjacent to the placenta, the columella, and the cells surrounding the vascular bundle. Except around the vascular tissue, the localization of sucrose synthase mRNA positively correlates with starch granule accumulation at the cellular level.

Differences in regulation of carbohydrate metabolism during early fruit development between domesticated tomato and two wild relatives

“…The major form of sucrose synthase mRNA in young tomato fruits comes from the sus2 gene and increased dramatically from DAP 5 to DAP 20 in fruits of S. lycopersicum and similarly in S. peruvianum. In contrast to our Wndings, Wang et al (1994) reported that sucrose synthase mRNA reached peak levels in fruits 5-7 days after anthesis. In that case, though, no distinction was made between sus3 and sus2 mRNA, but at that stage in development, sus2 is more highly expressed than sus3.…”

Divergent Fructokinase Genes Are Differentially Expressed in Tomato

“…In addition, the spatial expression of Sue synthase mRNA correlates with starch granule accumulation (Wang et al, 1994). The Frk2 mRNA is also expressed at high levels during this same developmental stage.…”

“…In tomato (Lycopersicon esculentum) starch accumulates during the early stage of fruit development and then decreases during maturation (Yelle et al, 1988). SUC synthase has been proposed to be the primary enzyme in the metabolism of imported Suc during the early developmental stages, and localization of its mRNA suggests a relationship between SUC synthase and starch granule accumulation (Wang et al, 1993(Wang et al, , 1994. In addition, invertase has been identified in the intercellular fraction, and it is suggested that hexose produced by invertase is actively imported across the plasma membrane (Sato et al, 1993;Ruan and Patrick, 1995).…”

Organ-Specific Differential Regulation of a Promoter Subfamily for the Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase Small Subunit Genes in Tomato

“…It is not known, however, whether the different tissues of tomato fruit have different sink status at early stages of development. Wang et al (1994) have analyzed the pattern of SUC synthase mRNA distribution in developing tomato fruit as a marker for sink tissue activity. Interestingly, the highest leve1 of Suc synthase mRNA and the highest concentration of starch were found in the pericarp and columnella tissues.…”