Abstract
BackgroundSucrose phosphate synthase (SPS) is an important component of the plant sucrose biosynthesis pathway. In the monocotyledonous Poaceae, five SPS genes have been identified. Here we present a detailed analysis of the wheat SPSII family in wheat. A set of homoeologue-specific primers was developed in order to permit both the detection of sequence variation, and the dissection of the individual contribution of each homoeologue to the global expression of SPSII.ResultsThe expression in bread wheat over the course of development of various sucrose biosynthesis genes monitored on an Affymetrix array showed that the SPS genes were regulated over time and space. SPSII homoeologue-specific assays were used to show that the three homoeologues contributed differentially to the global expression of SPSII. Genetic mapping placed the set of homoeoloci on the short arms of the homoeologous group 3 chromosomes. A resequencing of the A and B genome copies allowed the detection of four haplotypes at each locus. The 3B copy includes an unspliced intron. A comparison of the sequences of the wheat SPSII orthologues present in the diploid progenitors einkorn, goatgrass and Triticum speltoides, as well as in the more distantly related species barley, rice, sorghum and purple false brome demonstrated that intronic sequence was less well conserved than exonic. Comparative sequence and phylogenetic analysis of SPSII gene showed that false purple brome was more similar to Triticeae than to rice. Wheat - rice synteny was found to be perturbed at the SPS region.ConclusionThe homoeologue-specific assays will be suitable to derive associations between SPS functionality and key phenotypic traits. The amplicon sequences derived from the homoeologue-specific primers are informative regarding the evolution of SPSII in a polyploid context.
Highlights
Sucrose phosphate synthase (SPS) is an important component of the plant sucrose biosynthesis pathway
Except for SPPIII, the sucrose phosphate phosphatase (SPP) genes were expressed throughout plant development, their level tended to be highest in the developing anther and developing caryopsis (Figure 1)
Note that in the Arabidopsis thaliana mutant kns2-1, an altered SPS glycosyltransferase I domain disrupts the function of sucrose synthesis, and this leads to changes in the synthesis of the pollen primexine or callose [20]
Summary
Sucrose phosphate synthase (SPS) is an important component of the plant sucrose biosynthesis pathway. Under stressful conditions (e.g, low temperature or drought ), In important crop plants like maize, rice and sugarcane, plant growth and productivity have been correlated with SPS activity. SPS activity has been correlated with sucrose accumulation in sugarcane stems [6,7,8], while in maize, correlations have been demonstarted with vigour and biomass yield [9,10]. In tobaccco lines engineered to over-express SPS, UDP- glucose pyrophosphorylase and sucrose synthase, plant height was increased and flowering time delayed [15], while the heterologous expression of AtSPS induced longer stems and greater biomass [16]. The over-expression of ZmSPS in potato was shown to improve a number of yield-realted characters [17], while in tomato, it altered the pattern of carbohydrate partitioning in the leaf [18]
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