Carbohydrate metabolism of vegetative and reproductive sinks in the late-maturing peach cultivar 'Encore'

Abstract

Activities of NAD(+)-dependent sorbitol dehydrogenase (SDH), sorbitol oxidase (SOX), sucrose synthase (SS), acid invertase (AI), and neutral invertase (NI) in 'Encore' peach (Prunus persica L.) fruits and developing shoot tips were assayed during the growing season to determine whether carbohydrate metabolizing enzymes could serve as indicators of sink strength. In fruit flesh, SS activity was detected during Stage I of growth, when cells were actively dividing, and SDH activity was detected during Stage III, when cells were actively enlarging. Acid invertase activity was detected during Stage I and showed a closer correlation with relative increase in fruit weight during the growing season than SS activity. During seed filling and pit hardening (Stage II), when relative fruit growth rate was slowest, activities of carbohydrate metabolizing enzymes in fruit flesh were not detectable. No SOX activity was detected during Stages I and II. The highest sucrose content occurred near the end of fruit development when the activities of sucrose metabolizing enzymes were low. In developing shoot tips, the sorbitol:sucrose ratio was 2:1 (w/w) and SDH activity was low at the beginning and end of the season when vegetative growth was slowest. The sorbitol:sucrose ratio changed to 1:1 (w/w) along with an increase in SDH activity in shoot tips during the mid-growing season. In 'Nemaguard' peach, SDH exhibited higher activity in root tips than in other organs. Among the sorbitol- and sucrose-metabolizing enzyme activities, only SDH activity was positively correlated with shoot growth in 'Nemaguard' plants.

The high-quality draft genome of peach (Prunus persica) identifies unique patterns of genetic diversity, domestication and genome evolution

“…Accordingly, in Spiraeoideae, a previous study 22 described sorbitol transporters (SOT) that substantially increase sorbitol uptake, and in cherry, two SOT-encoding genes are known to have a major role in sorbitol accumulation 23 . Besides those encoding transporters, other key genes in sorbitol metabolism encode A6PR (aldose 6-P reductase, which is rate limiting for sorbitol biosynthesis) and SDH (sorbitol dehydrogenase), which converts the alcohol into sugars in fruits 24,25 . We found that in contrast to other species with sequenced genomes, apple and peach SDH and SOT are large gene families (Supplementary Table 17).…”

Cloning, Expression, and Characterization of Sorbitol Transporters from Developing Sour Cherry Fruit and Leaf Sink Tissues

“…NADSorDH has been purified and characterized (Yamaguchi et al, 1994), and its cDNA has been cloned (Yamada et al, 1998), but in some fruits there are multiple isoforms (Park et al, 2002). NAD-SorDH activities are sometimes correlated with fruit development and with sugar accumulation (Yamaguchi et al, 1994(Yamaguchi et al, , 1996Lo Bianco et al, 1999); however, such studies may be confounded if there are multiple isoforms. Immunoblot analysis has shown that enzyme protein levels were low in young apple fruit but then increased as fruit matured (Yamaguchi et al, 1996), and mRNA similarly increased during several stages of fruit development (Yamada et al, 1998).…”

“…However, a close relationship between NAD-SorDH activity and relative fruit growth rate could not be established in young apple tissues (Yamaguchi et al, 1996). Similarly, relationships between SorOX and fruit growth depend on stage of development (Lo Bianco et al, 1999). Thus, other enzymes, e.g.…”

Effect of CO₂ Enrichment on Growth and Flowering of <i>Phalaenopsis</i>

“…Temporal competition for carbohydrates appeared between vegetative and reproductive organs. The sucrose synthesis in the developing shoot tips of peaches reached the maximum when growth in fruits was lowest (Lo Bianco et al, 1999). In maize, ovary abortion under stress conditions is often a consequence of carbon starvation rather than a direct effect of these stresses (Mäkelä et al, 2005).…”