Abstract: In order to explore the characteristics of citrus sucrose-phosphate synthase（SPS）genes and their expression patterns during fruit development and ripening，four SPS genes（CsSPS1–CsSPS4）were identified in sweet orange genome. CsSPSs are distributed on different chromosomes and can be classified into three subfamilies，which also contain functional domains common in SPS family. Quantitative PCR revealed that CsSPSs were expressed in all tested tissues，and CsSPS4 preferentially expressed in fruit. Further study found that the expression levels of CsSPS3 and CsCSPS4 in‘Rongan’and‘Huapi’kumquat were higher than those of CsSPS1 and CsCSPS2 during the fruit development. In addition，the expression levels of CsSPS4 in the peel and pulp of two kumquats increased sharply with fruit development，suggesting its key functions in regulating sucrose synthesis and accumulation in kumquat fruit.

Key words: citrus, sucrose-phosphate synthase, sequence analysis, gene expression