GUS expression in Arabidopsis directed by 5' regions of the pea metallothionein-like gene PsMTA

Upstream sequences (including the first seven codons) of a metallothionein (MT)-like gene from pea, PsMTA, were fused to GUS and introduced into Arabidopsis. High-level GUS expression was detected in the roots of plants grown on MS medium, except in regions proximal to the root apex. There was precise delineation of the root-shoot boundary. In soil-grown plants there was low GUS expression and this was absent from the more mature regions of the roots. In the aerial tissues of soil-grown plants, GUS expression was restricted to hydathodes, stipules, expanding cotyledons and the following senescent tissues: leaves, cotyledons, petals, sepals, filaments, stigmas, nectaries and siliques. A 298 bp region was shown to be required for GUS expression in roots but not for expression in vegetative aerial tissues of plants grown on MS medium. This region contains predicted ethylene-responsive elements (EREs) but similar patterns of GUS expression were detected in etr1 seedlings. GUS expression was significantly higher in roots exposed to 500 nM copper, but this increase was small in proportion to expression in roots exposed to 50 nM copper.