The ASYMMETRIC LEAVES1 and ASYMMETRIC LEAVES2 genes regulate true leaf development through the repression of class 1 KNOX genes in Arabidopsis

Abstract

Leaves are developed from SAM as symmetrical and flat organs. To understand the process of the development of leaves at higher plants, we have analyzed phenotypes of two Arabidopsis thaliana mutant, asymmetric leaves1 (as1) and asymmetric leaves2 (as2). Mutant plants of as1 and as2 generate asymmetrical and downwardly curled leaves with aberrant mid veins and short petioles. Leaves of both mutants can regenerate ectopic shoot on the phytohormone-free medium. Furthermore the class 1 KNOX genes are ectopicaly expressed in leaves of these mutants. These suggest that AS1 and AS2 regulates the expression of class 1 KNOX genes negatively in leaves. To investigate the relationship between true leaf development and repression of class 1 KNOX by AS1 and AS2, we analyzed the phenotypes of the mutants that had various combinations of mutations in class 1 KNOX genes in addition to AS1 gene or AS2 gene.