Effects of BOR1 5′-UTR on the expression of the BOR1 ORF. Relative GUS activity (A) and GUS mRNA (B) are shown in roots of transgenic plants under toxic B conditions compared with those under low-B conditions. Schematic representations of the DNA constructs used for plant transformation are shown at left. Eight- or 9-d-old plants were transferred and incubated under 0.3 or 3,000 μm boric acid for 3 d. The values are those relative to the values at 0.3 μm boric acid, which was defined as 1 in each transgenic line. Means and medians were calculated with log-transformed values. Box plots show the distribution among six and four independent lines for UTRWT and UTR356-251, respectively. Diamonds indicate mean values. Asterisks indicate a significant difference compared with that resulting from the wild-type 5′-UTR (***, P < 0.001, Student’s t test).