title: Spermidine is a morphogenetic determinant for cell fate specification in the male gametophyte of the water fern Marsilea vestita.
abstract: Here, we show that the polyamine spermidine plays a key role as a morphogenetic determinant during spermatid development in the water fern Marsilea vestita. Spermidine levels rise first in sterile jacket cells and then increase dramatically in spermatogenous cells as the spermatids mature. RNA interference and drug treatments were employed to deplete spermidine in the gametophyte at different stages of gametogenesis. Development in spermidine-depleted gametophytes was arrested before the completion of the last round of cell divisions. In spermidine-depleted spermatogenous cells, chromatin failed to condense properly, basal body positioning was altered, and the microtubule ribbon was in disarray. When cyclohexylamine, a spermidine synthase (SPDS) inhibitor, was added at the start of spermatid differentiation, the spermatid nuclei remained round, centrin failed to localize into basal bodies, thus blocking basal body formation, and the microtubule ribbon was completely abolished. In untreated gametophytes, spermidine made in the jacket cells moves into the spermatids, where it is involved in the unmasking of stored SPDS mRNAs, leading to substantial spermidine synthesis in the spermatids. We found that treating spores directly with spermidine or other polyamines was sufficient to unmask a variety of stored mRNAs in gametophytes and arrest development. Differences in patterns of transcript distribution after these treatments suggest that specific transcripts reside in different locations in the dry spore; these differences may be linked to the timing of unmasking and translation for that mRNA during development.
authors.affiliation: Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland 20742, USA.
authors.forename: Faten
authors.initials: F
authors.lastname: Deeb
authors.forename: Corine M
authors.initials: CM
authors.lastname: van der Weele
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Wolniak
mesh_terms: D002454:Cell Differentiation / Q000502:physiology*; D003514:Cyclohexylamines / Q000378:metabolism; D020868:Gene Silencing; D043964:Marsileaceae / Q000166:cytology* / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D009024:Morphogenesis / Q000502:physiology*; D011058:Pollen / Q000166:cytology* / Q000502:physiology*; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013095:Spermidine / Q000378:metabolism*; D011436:Spermidine Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D003514:Cyclohexylamines; D012333:RNA, Messenger; D011436:Spermidine Synthase; D013095:Spermidine