The negative effect of nitrate on gametogenesis is independent of nitrate assimilation in Chlamydomonas reinhardtii

Planta. 2000 Jul;211(2):287-92. doi: 10.1007/s004250000291.

Abstract

The effect of nitrate on gamete differentiation as well as on the expression of genes involved in gametogenesis, nitrogen scavenging, and nitrate assimilation has been analyzed in wild-type and mutant strains of Chlamydomonas reinhardtii. Nitrate prevented gamete formation from wild-type strains and caused a strong reduction in the number of zygotes recovered in genetic crosses between nitrate-assimilation-deficient mutants, thus suggesting that nitrate by itself is providing a negative regulatory signal for the sexual differentiation of the alga. Addition of nitrate at low concentrations to wild-type cells, after an initial period of nitrogen starvation, resulted in a drastic decrease in transcript levels of both nitrate-assimilation genes (NIA1 and NRT2;1) and genes induced after N-starvation (NCG2 and NCG4). This strong effect of nitrate was due to its assimilation products since it was not evident in nitrate-assimilation mutants. A slight negative effect of nitrate on NCG4 expression was only observed in the mutant. Nitrate by itself was also found to provide a negative signal for the expression of gamete-specific genes (GAS3 and GAS18) in mutants incapable of assimilating nitrate.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Chlamydomonas reinhardtii / drug effects
  • Chlamydomonas reinhardtii / genetics
  • Chlamydomonas reinhardtii / physiology*
  • Crosses, Genetic
  • Gene Deletion
  • Gene Expression Regulation / drug effects
  • Gene Expression Regulation, Plant / drug effects
  • Genes, Plant
  • Genes, Protozoan
  • Germ Cells / physiology
  • Mutagenesis
  • Nitrates / metabolism*
  • Nitrates / pharmacology*
  • Zygote / drug effects
  • Zygote / physiology

Substances

  • Nitrates