Common and distinct mechanisms underlying the establishment of adaxial and abaxial polarity in stamen and leaf development

Establishment of adaxial-abaxial polarity is essential for lateral organ development. A stamen consists of a bilaterally symmetrical anther and a radial filament. Using a rice mutant, rod-like lemma, in which establishment of adaxial-abaxial polarity is compromised, we found that stamen patterning is likely to be achieved by a unique regulatory mechanism: rearrangement of adaxial-abaxial polarity in the anther, and abaxialization in the flament. These regulations are not found in leaf development. Here, we discuss similarities and differences between the stamen and the leaf in the mechanisms underlying the establishment of adaxial-abaxial polarity. In addition, we propose the idea that the process of establishing adaxial-abaxial polarity in lateral organs is likely to be divided into two phases: a meristem-dependent, followed by a meristem-independent phase. In stamen development, the transition between these two phases is clearly observed as the rearrangement of expression patterns of the adaxial and abaxial marker genes.