RNA gel-blot analysis to study the kinetics of UV-B induction of gene expression in 14-day-old roots. Lanes contained 10 μg total RNA extracted from roots after 2, 4, 6 or 8 h of UV-B (+) and no UV-B (-) treatments. Several identical gels were prepared and blotted. Each blot was hybridized with 32P-labeled membrane protein Mlo5 (a), receptor kinase (b) or transmembrane protein (c) probes. (d) Ethidium-bromide-stained gel as a check for equal loading. Bars in gray indicate light treatment without UV-B; bars in white indicate light treatment with UV-B supplementation for the time indicated in the figure.