Identification and expression profile analysis of the sucrose phosphate synthase gene family in Litchi chinensis Sonn.

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 of SPS gene families have been performed in Arabidopsis, rice, and sugarcane, but a comprehensive analysis of the SPS gene family in Litchi chinensis Sonn. has not yet been reported. In the current study, four SPS gene ( LcSPS1 , LcSPS2 , LcSPS3 , and LcSPS4 ) were isolated from litchi. The genomic organization analysis indicated the four litchi SPS genes have very similar exon-intron structures. Phylogenetic tree showed LcSPS1 - 4 were grouped into different SPS families ( LcSPS1 and LcSPS2 in A family, LcSPS3 in B family, and LcSPS4 in C family). LcSPS1 and LcSPS4 were strongly expressed in the flowers, while LcSPS3 most expressed in mature leaves. RT-qPCR results showed that LcSPS genes expressed differentially during aril development between cultivars with different hexose/sucrose ratios. A higher level of expression of LcSPS genes was detected in Wuheli, which accumulates higher sucrose in the aril at mature. The tissue- and developmental stage-specific expression of LcSPS1 - 4 genes uncovered in this study increase our understanding of the important roles played by these genes in litchi fruits.