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.
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Received: 21 July 1999 / Accepted: 13 December 1999
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Pozuelo, M., Merchán, F., Macías, M. et al. The negative effect of nitrate on gametogenesis is independent of nitrate assimilation in Chlamydomonas reinhardtii . Planta 211, 287–292 (2000). https://doi.org/10.1007/s004250000291
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DOI: https://doi.org/10.1007/s004250000291