Molecular cloning and expression analysis of a gene for a sucrose transporter maize (Zea mays L.)

Here we report the cloning of a sucrose transporter cDNA from maize (Zea ma ys L.) and an analysis of the expression of the gene. A cDNA clone (ZmSUT1) was identified as a sucrose transporter cDNA from its sequence homology at the amino acid level to sucrose transporters that have been cloned from ot her higher plant species. Based on the results of genomic Southern hybridiz ation, ZmSUT1 appears to be a single copy gene. A Northern blot analysis of seedlings and leaf blades suggests that the sucrose transporter is involve d in the export of accumulated carbohydrates from source leaf blades. From the measurements of transcript levels and carbohydrate contents in mature l eaf blades, we propose that the expression of the gene for the maize sucros e transporter is positively regulated by the amounts of soluble sugars such as sucrose and glucose in source leaves of maize. In addition, based on th e tissue specificity of the expression of the gene in maize plants at the r eproductive stage, it is possible that the sucrose transporter acts in sink tissues such as pedicels as well as in source tissues such as leaf blades.