ROLES FOR SUGAR SIGNAL DURING TUBEROUS ROOT DEVELOPMENT AND REGULATION OF SUGAR SIGNAL BY INVERTASE IN SWEET POTATO.

为了研究细胞壁结合转化酶在甘薯中的作用，作者从甘薯块根中克隆了一个细胞壁结合转化酶的cDNA，命名为IbCIN1。IbCIN1包含一个1746 bp的开放阅读框，编码577个氨基酸残基的多肽。推导出的氨基酸序列显示了细胞壁结合转化酶的典型特征，包括一个果糖苷酶基序和一个晶体氨酸催化位点。IbCIN1在幼根、块根和离块根中均有表达，而在发育叶片、成熟叶片、叶柄和匍匐茎中均无表达。在块根发育过程中，IbCIN1表达减少。6-苄基氨基嘌呤使IbCIN1 mRNA水平升高，糖对其影响不大。mRNA原位定位显示，IbCIN1优先表达于块根黄柏层。这些结果表明，IbCIN1在向块根黄柏层提供碳源或黄柏层分化中起重要作用。

To study roles of cell wall-bound invertase in sweet potato, I cloned a cDNA for cell wall-bound invertase, designated IbCIN1, from tuberous root of sweet potato. IbCIN1 contained an open reading frame of 1746 bp encoding a polypeptide of 577 amino acid residues. The deduced amino acid sequence showed typical features of the cell wall-bound invertases, including a fructosidase motif and a crysteine catalytic site. IbCIN1 was expressed in young root, tuberous root and root from tuberous root whereas no expression was observed in developing leaf blade, mature leaf blade, petiole and stolon. Expression of IbCIN1 decreased during developing of tuberous root. The level of mRNA for IbCIN1 was elevated by 6-benzylaminopurine, but was little affected by sugar. In situ localization of the mRNA revealed that, IbCIN1 is expressed preferentially in the phelloderm of tuberous root. These results suggest that IbCIN1 is important for supplying a carbon source to the phelloderm of tuberous root or differentiation of the phelloderm.