Figure 1.

Isolation of a temperature-sensitive root hair growth defect mutant. (A), Seven day-old seedlings were grown vertically in 1/4 MS media under 20°C and transferred to 30°C for 6 h, followed by 24 h recovery at 20°C. Bright field images were collected with a Nikon Eclipse E600 wide-field microscope with a 10× Plan Apo DIC (0.75 NA) lens. Dashed lines indicate root tip positions when seedling plants were transferred to 30°C for 6 h, and again when they were transferred back to 20°C. Scale bars = 200 µm. B, Localization of EYFP-RabA4b protein in growing root hair cells of fer-ts mutants at 20°C and 30°C. Medial root hair sections were collected using spinning-disk confocal microscopy from growing root hair cells of 7-d-old seedlings stably expressing EYFP-RabA4b in the fer-ts mutant in 20°C (left) or 30°C (right) using a Zeiss 40× Plan-Apochromat (1.3 NA) lens and appropriate EYFP fluorescence filter sets. Scale bars = 10 µm. Insets, magnified images to show details of EYFP-RabA4b subcellular localization in root hair tips. Scale bars = 2 µm. C, Quantification of root hair length in WT and fer-ts mutants under 20°C [WT {n = 392}, fer-ts {n = 454}] and 30°C [WT {n = 185}, fer-ts {n = 23}] conditions. D, Calculation of root hair densities in WT and fer-ts mutants at 20°C [WT {n = 392}, fer-ts {n = 454}] and 30°C [WT {n = 185}, fer-ts {n = 23}] in fully expanded primary roots of 7-d old plants. In each case, root hair lengths and densities were measured from n = 20 individual seedlings. Error bars represent sd. **P < 0.001 by Student’s t test.