Abstract
Land plants are of monophyletic origin from a charophycean green algae, whose plant body is gametophytic, except for a unicellular zygote, indicating that gametophytic and/or zygote-specific developmental genes are likely ancestral. One of the possible hypotheses for the evolution of genes involved in sporophyte development is that they were involved in unknown functions in gametophytes and/or zygotes, and were subsequently recruited for sporophyte development during the course of land plant evolution as the sporophyte came to dominate the gametophyte. We will discuss on this hypothesis based on (1) origin of MADS-box genes was in egg and sperm differentiation in haploid generation, (2) expression analyses of all Arabidopsis MADS-box genes in both hapoloid and diploid generations, (3) comparison of the moss Physcomitrella patens transcriptome to Arabidopsis genome, and (4) functional comparisons of SHOOT MERISTEMLESS gene and auxin polar transport between diploid shoot of angiosperms and haploid shoot of mosses.
