Structure and Expression Analysis of Sucrose Phosphate Synthase, Sucrose Synthase and Invertase Gene Families in Solanum lycopersicum

Sucrose phosphate synthase (SPS), sucrose synthase (SUS) and invertase (INV) are all encoded by multigene families. In tomato (Solanum lycopersicum), a comprehensive analysis of structure characteristics of these family genes is still lacking, and the functions of individual isoforms of these families are mostly unclear under stress. Here, the structure characteristics of the three families in tomato were analyzed; moreover, as a first step toward understanding the functions of isoforms of these proteins under stress, the tissue expression pattern and stress response of these genes were also investigated. The results showed that four SPS genes, six SUS genes and nineteen INV genes were identified in tomato. The subfamily differentiation of SlSPS and SlSUS might have completed before the split of monocotyledons and dicotyledons. The conserved motifs were mostly consistent within each protein family/subfamily. These genes demonstrated differential expressions among family members and tissues, and in response to polyethylene glycerol, NaCl, H2O2, abscisic acid or salicylic acid treatment. Our results suggest that each isoform of these families may have different functions in different tissues and under environmental stimuli. SlSPS1, SlSPS3, SlSUS1, SlSUS3, SlSUS4, SlINVAN5 and SlINVAN7 demonstrated consistent expression responses and may be the major genes responding to exogenous stimuli.

Primer Design for Isolation of Sucrose:Sucrose 1-Fructosyltransferase (1-SST) Gene from Gembili (Dioscorea esculenta)

Recent studies have reported the presence of inulin, a prebiotic polysaccharide, in gembili (Dioscorea esculenta). Sucrose:sucrose 1-fructosyltransferase (1-SST) is an enzyme that catalyzes the first step of inulin biosynthesis. The identification of this enzyme would be the foundation to improve the yield of inulin in gembili; to modify 1-SST gene for this purpose, its sequence must first be determined. This study aimed to design primers to isolate 1-SST gene from D. esculenta. The primers were designed by using the whole-genome sequence of Dioscorea rotundata due to the lack of genomic information on D. esculenta. Sequences from chromosome 6 and 11 were used as the template of primer design in which four pairs of primers were selected. Amplification products with expected size were gel-purified, then the targets were sequenced and analyzed in-silico. As a result, one of the primer pairs had successfully isolated vacuolar invertase gene, which is closely related to 1-SST gene. On the other hand, the other primer pairs showed either negative or false-positive result. Using the current strategy, 1-SST gene sequence from D. esculenta has not been successfully isolated, thus other approaches in primer design should be considered in further studies. Keywords: 1-SST, Dioscorea esculenta, Gembili, Inulin, Primer design

Deletion of beta-fructofuranosidase (invertase) genes is associated with sucrose content in Date Palm fruit

The fruit of date palm trees are an important part of the diet for a large portion of the Middle East and North Africa. The fruit is consumed both fresh and dry and can be stored dry for extended periods of time. Date fruits vary significantly across hundreds of cultivars identified in the main regions of cultivation. Most dried date fruit are low in sucrose but high in glucose and fructose. However, high sucrose content is a distinctive feature of some date fruit and affects flavor as well as texture and water retention. To identify the genes controlling high sucrose content we analyzed date fruit metabolomics for association with genotype data from 121 date fruits. We found significant association of dried date sucrose content and a genomic region that contains 3 tandem copies of the beta-fructofuranosidase (invertase) gene in the reference Khalas genome, a low sucrose fruit. High sucrose cultivars including the popular Deglet Noor had a homozygous deletion of two of the 3 copies of the invertase gene. We show the deletion allele is derived when compared to the ancestral allele that retains the all copies of the gene in 3 other species of Phoenix. The fact that 2 of the 3 tandem invertase copies are associated with dry fruit sucrose content will assist in better understanding the distinct roles of multiple date palm invertases in plant physiology. Identification of the recessive alleles associated with end-point sucrose content in date fruit may be used in selective breeding in the future.