juurekübara rakkudest sekreteeritav valk, mis inhibeerib rakkude diferentseerumist juure tipumeristeemis, reguleerides auksiinidest ja tsütokiniinidest sõltuvate signaaliradade geenide aktiivsust, CLE genes encode the development of roots and shoots, size and form of leaves in Arabidopsis and belong to the signal protein family. CLE40 is a protein secreted in the root cap cells that inhibits cell differentiation in the root apical meristem by regulating the activity of the genes controlled by auxins and cytokinins.