Figure 1.

gtl1 T-DNA Insertional Mutations Enhance Survival and Maintenance of Leaf RWC under Water Deficit Stress.

(A) The schematic illustrates T-DNA locations in the first exon (black bar) and the first intron (black line) in GTL1 for gtl1-4 and gtl1-5, respectively. Hatched bars indicate 5′- and 3′-untranslated regions. Arrows indicate the positions of primers used in (B).

(B) Homozygosity of the T-DNA insertion in glt1-4 and gtl1-5 was determined by PCR analysis of the GTL1 genomic fragment using left primers (LP) and right primers (RP) and the T-DNA insertion using a T-DNA–specific left border primer (LB) with LP for gtl1-4 and LB with RP for gtl1-5. Col-0 is the wild type.

(C) GTL1 expression level in wild-type, gtl1-4, and gtl1-5 plants was determined by RT-PCR analysis with forward and reverse primers (GTL1F and GTL1R) and ACTIN2 (ACT2; reference standard).

(D) and (E) Plant water stress responses were analyzed in 3-week-old wild-type and gtl1 (gtl1-4 and gtl1-5) plants grown under a long-day photoperiod (16 h light/8 h dark, 30% relative humidity). Five containers of each genotype (20 plants/container) were evaluated in three independent experiments. Relative SWC is the soil water relative to the soil water at day 0 of withholding water and is the average of five containers (see Supplemental Figure 1B online). The photograph in (D) illustrates results of one replicate from one experiment. Plant survival (E) was determined 4 d after rewatering (mean ± se, n = 5).

(F) In a separate experiment, 4-week-old wild-type and gtl1 plants were grown under a short-day photoperiod (8 h light/16 h dark, 60% relative humidity) and exposed to water deficit stress by withholding water. Leaf RWC (mean ± se, n = 3 to 4) and relative SWC (see Supplemental Figure 1C online) were determined. In (E) and (F), mean values of gtl1-4 and gtl1-5 plants are significantly different from the wild type at *P < 0.05 and **P < 0.01.