Identification and expression profile analysis of the sucrose phosphate synthase gene family inLitchi chinensisSonn.

Sucrose phosphate synthase (SPS, EC 2.4.1.14) is a key enzyme that regulates sucrose biosynthesis in plants. SPS is encoded by different gene families which display differential expression patterns and functional divergence. Genome-wide identification and expression analyses ofSPSgene families have been performed in Arabidopsis, rice, and sugarcane, but a comprehensive analysis of theSPSgene family inLitchi chinensisSonn. has not yet been reported. In the current study, fourSPSgene (LcSPS1,LcSPS2,LcSPS3, andLcSPS4) were isolated from litchi. The genomic organization analysis indicated the four litchiSPSgenes have very similar exon-intron structures. Phylogenetic tree showedLcSPS1-4were grouped into different SPS families (LcSPS1andLcSPS2in A family,LcSPS3in B family, andLcSPS4in C family).LcSPS1andLcSPS4were strongly expressed in the flowers, whileLcSPS3most expressed in mature leaves. RT-qPCR results showed thatLcSPSgenes expressed differentially during aril development between cultivars with different hexose/sucrose ratios. A higher level of expression ofLcSPSgenes was detected in Wuheli, which accumulates higher sucrose in the aril at mature. The tissue- and developmental stage-specific expression ofLcSPS1-4genes uncovered in this study increase our understanding of the important roles played by these genes in litchi fruits.