Figure 4: NatA-depleted Arabidopsis plants display drought tolerance.

Wild-type (same age) and NatA-depleted plants were grown for 42 days on soil under short-day conditions and subsequently challenged with drought for 20 days. Twety-eight-day-old wild-type plants (same size) served as an additional control to test the impact of developmental stage on the tolerance against drought. (a) Growth phenotype of wild-type and NatA-depleted plants grown under control conditions or drought stress for 20 days (Scale bar, 4 cm). (b) RWC in leaves of wild-type, amiNaa10 and amiNaa15 plants during application of drought stress. Data are represented as mean±s.d. (N=4). (c) Transpiration of leaves from 6-week-old wild-type and NatA-depleted plants. Data are represented as mean±s.d. (N=3). (d) Top view on single stomata from wild-type and NatA-depleted plants (Scale bar, 20 μm). (e) Fluorescent staining of hydrogen peroxide in guard cells of wild-type and NatA-depleted plants (Scale bar, 40 μm). (f) Quantification of hydrogen peroxide-dependent fluorescence by confocal laser scanning microscopy in guard cells of wild type and NatA depleted in absence or presence of 50 μM ABA. Wild type and NatA depleted were grown on soil under short-day condition with regular water supply for 6 weeks before analysis. Data are represented as mean±s.e. Asterisks indicate significant differences to wild type. (P<0.05, N=10–80, Student’s t-test) (g) Root-to-shoot ratio of wild-type, naa20 and NatA-depleted plants grown hydroponically on ½ Hoagland medium for 6 weeks under short-day conditions. Asterisks indicate significant differences to wild type determined by Student’s t-test. Data are represented as mean±s.d. (P<0.05, N=30–35), Student’s t-test). (h) Root phenotype of 2-week-old wild-type and NatA-depleted plants grown under short-day conditions on solid ½ MS-medium (Scale bar, 0.5 cm). Arrows indicate lateral roots.