ASYMMETRIC LEAVES2 and FASCIATA2 cooperatively regulate the formation of leaf adaxial-abaxial polarity in Arabidopsis thaliana.

摘要

The establishment of adaxial-abaxial polarity in the early stage of leaf development is important for the expansion of lamina. In Arabidopsis thaliana, asymmetric leaves2 (as2) and as1 mutations cause defects in the leaf adaxial-abaxial polarity, which are exhibited as abaxialized filamentous leaves in the various modifier mutant backgrounds. Several modifier single mutants generate pointed leaves in common. Mutations in FASCIATA2 (FAS2) also cause pointed leaves. The FAS2 gene encodes a component of Chromatin Assembly Factor-1 (CAF-1), a histone chaperone, which affects mRNA levels of various genes through the regulation of chromatin states. In the present study, we demonstrate that as2 fas2 double mutants frequently generate abaxialized filamentous leaves and show increased mRNA levels of genes for leaf abaxialization, KANADI1 (KAN1), KAN2, YABBY5 (YAB5), ETTIN/AUXIN RESPONSE FACTOR3 (ETT/ARF3) and ARF4. In addition, the transcript levels of all four class 1 KNOTTED1-like homeobox genes that are involved in the maintenance of shoot apical meristem and the Kip-related Protein2 (KRP2) and KRP5 genes that are involved in the cell cycle progression are elevated in the as2 fas2. The mRNA levels of all genes other than YAB5, whose transcript levels rise in as2 fas2, were increased in the fas2 single mutants. Our data suggest that FAS2 participates in the establishment of leaf adaxial-abaxial polarity through the repression of the transcript levels of these genes on the as2 background.