Analysis of promoter activity of cotton lipid transfer protein gene LTP6 in transgenic tobacco plants

A cotton (Gossypium hirsutum) genomic clone (1.7-kb DNA insert) harboring t he lipid transfer gene Ltp6 specifically expressed in fiber cells had been previously isolated and characterized. By using PCR amplification, the 447 bp Ltp6 promoter and a series of 5' deletions of the promoter were generate d and cloned into a pBI101 plasmid upstream of the GUS (beta-glucuronidase) reporter gene. These constructs were introduced into Agrobacterium tumefac iens LBA4404, and leaf disks of tobacco (Nicotiana tabacum L.) were transfo rmed with A. tumefaciens LBA4404 carrying various promoter-GUS pBI101 plasm ids, Histochemical analyses of the transgenic tobacco seedlings indicated t hat the Ltp6 promoter (from nt - 447 to - 1, undeleted) directed GUS expres sion only in trichomes (hair cells). Fluorometric GUS assays showed that th e promoter activity of the undeleted Ltp6 promoter was at least 1000 times weaker than that of the 35S promoter of cauliflower mosaic virus (CaMV). Se quential deletions of the promoter gradually decreased the expression level of the GUS gene. No GUS activity was observed when the 5' deletion of the Ltp6 promoter reached to nt - 86, which removed the putative CAAT and TATA promoter elements. (C) 1999 Elsevier Science Ireland Ltd. All rights reserv ed.