Figure 4. Metazachlor alters root gravitropism and targets KCS9 KCS2 and KCS20.

(a) Root angle curvature towards the new gravity vector 24 h following a gravistimulation (turn the plate of 90°) is calculated, we then ranked the effective (n) into classes of 15° angles (0° was the exact direction of the new gravity vector) and represented each class of angles in a circular chart. (b) In untreated roots, reorientation of roots 24 h after a gravistimulation is very close to the gravity vector, whereas in 50 nM metazachlor-treated roots (c) this reorientation is much less efficient (n=110 roots per experiment). (d–i) As compared with untreated roots (d), the kcs2,20 double mutant (f) and kcs9 single mutant (h) do not display gravitropism phenotype. On 25 nM metazachlor treatment, kcs2,20 double mutant (g) and kcs9 single mutant (i) display obvious root gravitropism phenotype, whereas wild-type roots treated with 25 nM of metazachlor (e) do not react. Hence, kcs2,20 double mutant (f,g) and kcs9 single mutant (h,i) are hypersensitive to metazachlor in respect to root gravitropism (n=55 roots per experiment).