Objective  This study explored the key genes of sweet corn sweetness formation and the possible molecular mechanism of heterosis.

  Method  Genotypes and expressions of sucrose synthase gene family of a super-sweet corn variety, Minshuangse No.6, and its parents were analyzed using bioinformatics, resequencing, transcriptome, and other techniques to unveil the underlining basis of the sweet taste of corns.

  Result  Eighteen sucrose synthase genes were isolated from the corn kernels. Among them, Zm0001d029087 was found to belong to the same subfamily as Sh1, Sus1, and Sus2/3 with close evolution relationships. It might play a role in the sugar metabolism of the corn. Comparing both parents with B73, mutations were found in Sh1, Sus1, and Sus2/3. Of the 18 genes, only Zm0001d029087 and those 4 genes expresses in the kernels. Further analyses showed the 4 genes, except Sh1, had significantly lower expressions in Minshuangse No.6 than in both or one of the parents.

  Conclusion  The genetic variations in the super-sweet Minshuangse No.6 revealed a unique characteristic of Zm0001d029087 that might relate to the sweetness of the corn kernels. A preliminary role of heterosis in sugar formation by that gene was proposed for further investigation.