title: Morphology and ploidy level determination of Pteris vittata callus during induction and regeneration.
abstract: BACKGROUND
  Morphological and ploidy changes of the arsenic hyperaccumulator, Chinese brake fern (Pteris vittata) callus tissue are described here to provide insight into fern life cycle biology and for possible biotechnology applications. Pteris vittata callus was studied using transmission and scanning electron microscopy, and flow cytometry.
  
  
  RESULTS
  Callus induction occurred both in light and dark culture conditions from prothallus tissues, whereas rhizoid formation occurred only in dark culture conditions. Callus tissues contained two types of cells: one actively dividing and the other containing a single large vacuole undergoing exocytosis. Sporophytes regenerated from callus asynchronously form clusters of cells in a manner apparently analogous to direct organogenesis. Extracellular matrices were observed in actively-growing callus and at the base of regenerating sporophytes. Callus tissue nuclei were found to be primarily diploid at induction and throughout maintenance of cultures indicating that callus cell fate is determined at induction, which closely follows apogamous sporophyte development. Presence of a dense extracellular matrix in conjunction with sporophyte development suggests a link between the suspensor-like activity of the embryonic foot during normal fern embryo development and the suspected functions of extracellular matrices in angiosperms.
  
  
  CONCLUSIONS
  Further investigation could lead to a better understanding of genes involved in P. vittata embryo development and apogamous sporophyte development. The methodology could be useful for in vitro propagation of rare and valuable fern germplasm.
authors.affiliation: Department of Plant Sciences, The University of Tennessee, Knoxville, Tennessee, 37996, USA. bjoyce3@gmail.com.
authors.forename: Blake L
authors.initials: BL
authors.lastname: Joyce
authors.affiliation: Center for Wildlife Health, Department of Forestry, Wildlife and Fisheries, the University of Tennessee, Knoxville, Tennessee, 37996, USA. seda@utk.edu.
authors.forename: Shigetoshi
authors.initials: S
authors.lastname: Eda
authors.affiliation: Advanced Microscopy and Imaging Center, The University of Tennessee, Knoxville, TN, 37996, USA. jrdunlap@utk.edu.
authors.forename: John
authors.initials: J
authors.lastname: Dunlap
authors.affiliation: Department of Plant Sciences, The University of Tennessee, Knoxville, Tennessee, 37996, USA. nealstewart@utk.edu.
authors.forename: C Neal
authors.initials: CN
authors.lastname: Stewart
mesh_terms: D001151:Arsenic / Q000378:metabolism; D018929:Cell Culture Techniques; D011003:Ploidies; D032495:Pteris / Q000235:genetics* / Q000254:growth & development* / Q000502:physiology; D012038:Regeneration
chemical_list: D001151:Arsenic