Figure 1.
Reduced ABA accumulation of Sha relative to Ler is controlled by a single QTL that includes NCED3 alleles of differing function. A, Time course of ABA accumulation after transfer of 7-d-old Ler and Sha seedlings from control media (−0.25 MPa) to low-ψw stress (−1.2 MPa). Data are means ± se (n = 6–9) combined from two independent experiments. Sha ABA levels were significantly lower than those of Ler (Student’s t test, P ≤ 0.05) at each time point except time 0 (unstressed control). The inset shows the ABA contents of Ler and Sha at 96 h after transfer to low ψw. B, ABA accumulation of Ler and Sha 96 h after transfer to moderate-severity low ψw (–0.7 MPa). Data are means ± se (n = 6–12) combined from three independent experiments. ABA contents of Ler and Sha were significantly different (Student’s t test, P ≤ 0.001). C, LOD plot of QTL mapping results. A single QTL was detected at the top of chromosome 3. The red chromosome diagram shows the positions of NCED3 and flanking markers within the QTL interval. D, F1 ABA analysis from Ler, Sha, and nced3 crosses. F1 seedlings from reciprocal crosses of Ler and Sha to nced3 were transferred to –1.2 MPa, and ABA was measured 24 h later. Boxes encompass the 25th to 75th percentiles, with the solid line indicating the median and the dashed line indicating the mean. Whiskers show the 10th and 90th percentiles, and dots indicate outliers. n = 16 for all genotypes. Significant differences (Student’s t test, P ≤ 0.05) are indicated by asterisks. E, ABA contents of transgenic lines expressing the Ler or Sha NCED3 genomic fragment (promoter, 5′ UTR, and coding region) in the nced3 mutant or Sha background. NCED3 was expressed either as untagged protein or with a C-terminal hemagglutinin (HA) tag. ABA was assayed 96 h after transfer to −1.2 MPa. Data are means ± se (n = 14) combined from three independent experiments. Immunoblots verifying the NCED3 expression level in each transgenic line are shown in Supplemental Figure S1. FW, Fresh weight.