Effects of silicon-limitation on growth and morphology of Triparma laevis NIES-2565 (Parmales, Heterokontophyta)

PLoS One. 2014 Jul 23;9(7):e103289. doi: 10.1371/journal.pone.0103289. eCollection 2014.

Abstract

The order Parmales (Heterokontophyta) is a group of small-sized unicellular marine phytoplankton, which is distributed widely from tropical to polar waters. The cells of Parmales are surrounded by a distinctive cell wall, which consists of several siliceous plates fitting edge to edge. Phylogenetic and morphological analyses suggest that Parmales is one of the key organisms for elucidating the evolutionary origin of Bacillariophyceae (diatoms), the most successful heterokontophyta. The effects of silicon-limitation on growth and morphogenesis of plates were studied using a strain of Triparma laevis NIES-2565, which was cultured for the first time in artificial sea water. The cells of T. laevis were surrounded by eight plates when grown with sufficient silicon. However, plate formation became incomplete when cells were cultured in a medium containing low silicate (ca. <10 µM). Cells finally lost almost all plates in a medium containing silicate concentrations lower than ca. 1 µM. However, silicon-limitation did not affect growth rate; cells continued to divide without changing their growth rate, even after all plates were lost. Loss of plates was reversible; when cells without plates were transferred to a medium containing sufficient silicate, regeneration of shield and ventral plates was followed by the formation of girdle and triradiate plates. The results indicate that the response to silicon-limitation of T. laevis is different from that of diatoms, where cell division becomes inhibited under such conditions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Wall / metabolism
  • Cell Wall / ultrastructure
  • Diatoms / cytology
  • Diatoms / growth & development*
  • Diatoms / ultrastructure
  • Phytoplankton / cytology
  • Phytoplankton / growth & development*
  • Phytoplankton / ultrastructure
  • Silicon / metabolism*

Substances

  • Silicon

Grants and funding

A part of this study was supported by Grant-in-Aid for Scientific Research 23370046 (A. K.), the Canon Foundation (A. K.), and the Sasakawa Scientific Research Grant from the Japan Science Society (K. Y.). The data collection in this study was partially supported by above funders. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.