Fig. 2. Cell cycle marker activity in csn mutants. (A) CYCB1;1:GUS expression in primary roots (upper row) and root tips (lower row) of 7-day-old light-grown wild-type and csn3, csn4 and csn5ab Arabidopsis seedlings. (B,C) CYCB1;1:GUS expression in primary roots (upper row) and root tips (lower row) following 24 hours and 48 hours of treatment, respectively, with the synthetic auxin 2,4D. Arrowheads indicate lateral root primordia. (D) KN and CDKB1;1 accumulation in protein extracts (20 µg) of 2-day-old wild-type seedlings and 7-day-old csn3, csn4 and csn5ab mutant seedlings. A cross-reacting band was used as a loading control. Relevant bands are indicated by arrowheads. Wild-type and mutant plants of different ages were used for this analysis because 2-day-old wild-type and 7-day-old mutant seedlings are comparable in size and contain a comparable number of dividing cells. Scale bars: 1 mm in wild type; 0.5 mm in csn3, csn4 and csn5ab.