Abstract

In the green alga Chlamydomonas reinhardtii Dangeard a shift in nitrogen source from ammonium to nitrate results in the rapid induction of the mitochondrial alternative oxidase (AOX). It has been hypothesized that this induction compensates for the increased generation of ATP in the chloroplast. Based upon light response curves of oxygen evolution, a shift from ammonium to nitrate resulted in a significant increase in both apparent quantum yield of oxygen evolution and photosynthetic capacity. Changes in chlorophyll a fluorescence including a decrease in both excitation pressure and nonphotochemical quenching were also observed over a 12 h nitrate shift. To investigate whether changes in chloroplast ATP generation were behind the nitrate-dependent induction of AOX, transcript and protein accumulation were monitored in cells grown under high, moderate and low irradiances. No major differences in Aox1 gene expression or AOX accumulation were found among the different light regimes. These data do not support the hypothesis that an increase in AOX within the mitochondrion in response to nitrate is tied to changes in photosynthesis occurring within the chloroplast.

Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call