Objective  CwSBEII in Eleocharis tuberosa was cloned to understand the functions and expressions of the gene in various tissues and corms at different expansion stages.

  Methods   The cDNA sequence of CwSBEII of Chinese water chestnut was cloned by RT-PCR, functions deciphered by bioinformatics, and spatiotemporal expressions in tissues and corms determined by fluorescence quantitative PCR.

  Results   CwSBEII had an ORF length of 2 547 bp encoding 848 amino acids. The molecular weight of this unstable hydrophilic protein was 96 100.52 Da with a theoretical pI of 5.24, an instability index of 41.07, and a GRAVY reading at −0.473. It was closely related to and clustered with the SBEIIs of wheat (Triticum aestivum), rice (Oryza sativa), and maize (Zea Mays) of the grass family. Although found in the roots, leaves, peels as well as corm, CwSBEII was most highly expressed in the leaves and significantly upregulated in the early stage of corm expansion of Chinese water chestnut.

  Conclusion  CwSBEII was specifically expressed in various tissues of Chinese water chestnut and most highly in the leaves. It was significantly upregulated during the early stage of corm expansion and might play an important role in the starch synthesis of E. tuberosa.