A storage protein gene from taro shows tuber‐specific expression in transgenic potato

Abstract

Tarin is a family of storage proteins of Mr 12 500 that accounts for approximately 40% of the total soluble proteins in taro (Colocasia esculenta) corms. Besides its role as storage reserve, tarin may also act in defense responses. tar1, a gene encoding an isoform of tarin, was previously identified and it was shown to be expressed during corm development. To investigate the mechanisms involved in the regulation of tar1, transgenic tobacco and potato plants were produced. High levels of transcripts were found only in tubers of plants grown in the greenhouse. However, in vitro grown plants accumulated mRNA in both tubers and stems. It was also found that sucrose influenced tar1 expression in in vitro plants. Temporal expression of the tar1 gene varied, transcripts were not observed in stolons, but in all subsequent stages of potato development. These results suggest that the regulation of tar1 gene in potato mimics the regulation of potato storage protein genes. The tar1 promoter showed homology with patatin (potato storage protein) promoters. However, in transgenic tobacco, no expression was detected, indicating tuber specificity.