Untitled

Abstract

Sucrose synthase, which cleaves sucrose in the presence of uridine diphosphate (UDP) into UDP-glucose and fructose, is thought to be a key determinant of sink strength of heterotrophic plant organs. To determine the roles of the enzyme in carrot, we characterized carrot sucrose synthase at the molecular level. Two genes (Susy*Dc1 and Susy*Dc2) were isolated. The deduced amino acid sequences are 87% identical. However, the sequences upstream of the translation initiation codons are markedly different, as are the expression patterns of the two genes. Susy*Dc2 was exclusively expressed in flowers. Transcripts for Susy*Dc1 were found in stems, in roots at different developmental stages, and in flower buds, flowers and maturing seeds, with the highest levels in strong utilization sinks for sucrose such as growing stems and tap root tips. Expression of Susy*Dc1 was regulated by anaerobiosis but not by sugars or acetate. The carrot sucrose synthase protein is partly membrane-associated and this insoluble form may be directly involved in cellulose biosynthesis. Tap roots of the carrot cultivar used accumulated starch in the vicinity of the vascular bundles, which correlated with high sucrose synthase transcript levels. This finding suggests that soluble sucrose synthase in tap roots channels sucrose towards starch biosynthesis. Starch accumulation appears to be transient and may be involved in sucrose partitioning to developing tap roots.

Analyses of the sucrose synthase gene family in cotton: structure, phylogeny and expression patterns

“…Unrooted phylogenetic tree of plant Sus proteins constructed using the neighbor-joining method with MEGA 5.0 program. Isozymes and corresponding plant species are: cotton, GaSus1 to 7 (this study); Potato, StSus1 to 4 [9]; Pea, PeaSus1 to 3 [13]; Wheat, TaSus1 and TaSus2 [15]; Arabidopsis thaliana , AtSus1 to 6 [23]; Rice, OsSus1 to 6 [24]; Lotus japonicus , LjSus1 to 6 [25]; Citrus, CitSus1, CitSus2 and CitSusA [29]; Bamboo, BoSus1 to 4 [37]; Tomato, LeSus1 and LeSus2 [38]; Carrot, DcSus1 and DcSus2 [39]; Maize, ZmSh1, ZmSus1 and ZmSus3 [40]; Barley, HvSus1 and HvSus2 [41]; Sugarbeet, SbSS1 [42]; Sorghum, SbSus2 (accession no. FJ513325); Sugarcane, SoSus2 (accession no.…”

Exploring the neutral invertase–oxidative stress defence connection in Arabidopsis thaliana

“…At-A/N-InvA, At1g56560; At-A/N-InvG, At1g35580 (Qi et al , 2007; Lou et al , 2007); At-A/N-InvF, At1g72000; At-A/N-InvH, At3g05820; At-A/N-InvC, At4g06500; At-A/N-InvI, At4g09510 (Barratt et al , 2009); At-A/N-InvE, At5g22510 (Vargas et al , 2008); At-A/N-InvD, At1g22650; At-A/N-InvB, At4g34860; AsinvA, Anabaena sp. PCC 7120 (Vargas et al , 2003); BvINV, Beta vulgaris (González and Cejudo, 2007); DcINV, Daucus carota (Sturm et al , 1999); LjInv1, Lotus japonicus (Flemetakis et al , 2006); LtINV, Lolium temulentum (Gallagher and Pollock, 1998); OsNIN1 and OsNIN3, Oryza sativa (Murayama and Handa, 2007; Jia et al , 2008); Ta-A/N-INV, Triticum aestivum (Vargas et al , 2007). Referring to the (putative) subcellular localization of the enzymes, the confidence levels generated by target P are indicated.…”

“…Possibly, TRIS mimicks a so far unidentified inhibitor acting in planta . A/N-Inv genes have been studied in Arabidopsis thaliana (Ji et al , 2005), Lolium temulentum (Gallagher and Pollock, 1998), Daucus carota (Sturm et al , 1999), Beta vulgaris (Gonzalez and Cejudo, 2007), Oryza sativa (Murayama and Handa, 2007), and Anabaena cyanobacterium (Vargas et al , 2003). …”

Cold Treatment Breaks Dormancy but Jeopardizes Flower Quality in Camellia japonica L.

“…Accordingly, the strong decrease of CjSuSy in flower bud and leaf tissues during the treatment could indicate a down-regulation caused by sucrose depletion ( Koch et al, 1992 ). The successfully isolated partial gene CjSuSy had the highest similarity with the Daucus carota SuSy isoform 1 that encodes for a sucrose-cleaving enzyme that provides UDP-glucose and fructose and is expressed in several tissues, including flower buds ( Sebková et al, 1995 ; Sturm et al, 1999 ). In Arabidopsis , the induction of several SuSy isoforms has been found under conditions of increased demand for translocation of carbohydrates such as O 2 deficiency, dehydration, osmotic stress, and cold treatment ( Baud et al, 2004 ).…”

“…When dormancy requirements are fulfilled, the flower bud becomes a strong sink for assimilates. Sucrose synthase (SuSy) gene family has been found to encode for primary metabolism sucrose-cleaving enzymes whose up-regulation is expected in strong utilization sinks for sucrose ( Sturm et al, 1999 ; Baud et al, 2004 ). In Camellia , the anthocyanin pathway will be up-regulated for flower pigmentation.…”