Genetic Analysis Of Krt1, An As2 Enhancer, And The Molecular Cloning Of KRT1

The polarity development of leaves is important for their normal functions. There are three main polarity axes: adaxial-abaxial axis, proximal-distal axis, medial-lateral axis. Among these the adaxial-abaxial polarity plays the most prominent role. The ASYMMETRIC LEAVES2 (AS2) gene in Arabidopsis promotes adaxial development and the leaves of as2 mutants are abaxialized. In order to further elucidate the molecular mechanism AS2 uses in shaping the polarity of leaves, we carried out EMS mutagenesis of as2 mutants and screened for modifiers that would change the phenotype of as2. Here we report an as2 enhancer, krt1, which aggravated the leaf polarity defects of as2. krt1 as2 double mutants produced more severely abaxialized leaves than as2 single muants. KRT1 encodes the RPN2a subunit of the 26S proteasome, which means that krt1 may interfere with the normal proteolytic functions of the 26S proteasome. The identification of krt1 as an as2 enhancer demonstrates that leaf polarity development has another level of post-translational regulation that previously has not been much studied.Besides interacting with as2, krt1 can also enhance the phenotypes...