Figure 9.

Effect of osmotic stress on BAM mRNA and activity and reducing sugars in crude leaf extracts from 5-week-old Arabidopsis plants. A and B, RT-PCR analysis of total RNA isolated from wild-type plants watered with 200 mL of nutrient solution alone or nutrient solution supplemented with 200 mm mannitol (+) and examined after 2 (A) or 4 (B) d. RNA was probed with primers specific for BAM1 or BAM3 mRNA (expected sizes for respective amplicon bands are indicated at the side of the gel). Hsp70 mRNA was also probed as a positive control for osmotic stress. Arrowheads indicate the internal control. C and D, Total BAM activity in bam5, bam5/1, and bam5/3 leaves from similarly treated plants. Assays were conducted at 22°C with soluble starch as the substrate. E and F, Total reducing sugars in the same leaf extracts used for the BAM assays. Black bars represent control plants, and gray bars represent treated plants. Each graph represents developmentally matched plants, but the 2- and 4-d experiments were conducted with different sets of plants. Each replicate included all of the leaves from three plants. Values are means ± sd (n = 3).