Sex and the single fern

摘要

Unlike animals, plants have two alternating generations: a diploid sporo-phyte and a haploid gametophyte. Through meiosis, the sporophyte produces haploid spores, which then give rise to gametophytes, a multi-cellular haploid structure that produees. gametes for sexual reproduction. All seed plants and some non-seed plants are hetero-sporous, producing spores of different sizes: large female spores and small male spores. Most ferns, on the other hand, are homo-sporous; they produce a single type of spore. After germination, each fern spore has the potential to develop into a male, female, or hermaphrodite gametophyte. The developmental decision that determines the sex of a particular gametophyte depends on an in-terplant communication system mediated by chemical signals, termed antheridiogens (7, 2). On page 469 of this issue, Tanaka et al. (3) show that an antheridiogen in the Japanese climbing fern (Lygodium japonicum) functions as more than a simple chemical signal. Covalent modification of the antheridiogen is required to trigger the fern's response to form male gametophytes. Temporal and spatial separation of the biosynthetic pathway between the early- and late-maturing gametophytes ensures the production of the antheridiogen, and the active male-inducing chemically modified form, at just the right time and place.