Ibα-XYL1 Interfered Expression Decreases Starch Granule Size and Increases Soluble Sugar Content to Improve Steamed Sweetpotato Storage Root Taste

As an important characteristic and horticultural crop in China, sweetpotato can be used as food, industrial raw material, vegetable, and ornamental material. Purple sweetpotato for table use is rich in anthocyanin, which leads to some bitter taste, so it needs further quality improvement. Genetic engineering technology is an effective method to improve crop traits, but there are few reports on genes that can improve sweetpotato sweetness and taste. A xylosidase gene (<i>Ibα-XYL1</i>) was cloned from sweetpotato variety 'Yanshu 25' with a fragment size of 2796 bp and encoding 932 amino acid sequences. It has a typical transmembrane domain and three functional domains, which are localized at cell membrane. Reduction in <i>Ibα-XYL1</i> gene expression had no significant effect on the expansion characteristics and anthocyanin content of sweetpotato storage root (SPSR), but it could up-regulate the expression of sucrose synthesis related genes (<i>SuS</i>, <i>SuPS</i>) and promote the accumulation of soluble sugar in fresh transgenic SPSR. At the same time, it could up-regulate the expression of genes related to starch synthesis modifications (<i>GASS</i>, <i>SBE</i>) and starch decomposition (<i>AMY</i> and <i>BAM</i>), reduce the starch granule size and the starch pasting temperature, promote the conversion of starch to maltose, increase the soluble sugar content, and improve the sweetness and taste of steamed transgenic SPSR. The results are of great significance for quality improvement of sweetpotato.