Plants face many environmental stresses. Among them, UV-B radiation can cause damage, thus decreasing growth and productivity. Genetic manipulation could improve the UV-B tolerance of plants.
Roots are essential for resource capture, plant stability, and anchorage, so the enhancement of root growth should increase yield. To identify rice genes that confer resistance to UV-B or promote root growth in rice FOX Arabidopsis lines, we screened several long-root mutants from ca. 7000 lines in the rice FOX Arabidopsis library by root-bending assay.
The root-bending assay was performed as described (1, 2) with modification. Seedlings were grown vertically on nutritive agar plates (1.2% [w/v] agar, 1x Gamborg”Ēs vitamin mixture, and 0.46% [w/v] MS salts) under continuous light (~40 µmol m-2 s-1) at 22 °C for 3 days. For analysis of UV-B sensitivity, seedlings were exposed to 7-8 kJ m-2 UV-B and then incubated under continuous white light for a further 3 d. After incubation, lines that had longer roots than the wild type (Columbia) were selected as candidate mutant lines. Candidates were screened a total of 3 times.
At the third screening, photographs were taken and root lengths were measured with Image J software (version 1.34, National Institutes of Health, USA). UV-B-tolerant and long-root mutants were identified as those with longer roots than the wild type.
1. Sakamoto et al. (2003) Plant Cell 15, 2042-2057
2. Takahashi et al. (2005) Plant Physiology 138, 870-881