RRC ID 74022
Author Giordano M, Goodman CA, Huang F, Raven JA, Ruan Z.
Title A mechanistic study of the influence of nitrogen and energy availability on the NH4+ sensitivity of nitrogen assimilation in Synechococcus.
Journal J Exp Bot
Abstract In most algae, NO3- assimilation is tightly controlled and is often inhibited by the presence of NH4+. In the marine, non-colonial, non-diazotrophic cyanobacterium Synechococcus UTEX 2380, NO3- assimilation is sensitive to NH4+ only when N does not limit growth. We sequenced the genome of Synechococcus UTEX 2380, studied the genetic organization of the nitrate assimilation related (NAR) genes, and investigated expression and kinetics of the main NAR enzymes, under N or light limitation. We found that Synechococcus UTEX 2380 is a β-cyanobacterium with a full complement of N uptake and assimilation genes and NAR regulatory elements. The nitrate reductase of our strain showed biphasic kinetics, previously observed only in freshwater or soil diazotrophic Synechococcus strains. Nitrite reductase and glutamine synthetase showed little response to our growth treatments, and their activity was usually much higher than that of nitrate reductase. NH4+ insensitivity of NAR genes may be associated with the stimulation of the binding of the regulator NtcA to NAR gene promoters by the high 2-oxoglutarate concentrations produced under N limitation. NH4+ sensitivity in energy-limited cells fits with the fact that, under these conditions, the use of NH4+ rather than NO3- decreases N-assimilation cost, whereas it would exacerbate N shortage under N limitation.
Volume 73(16)
Pages 5596-5611
Published 2022-9-12
DOI 10.1093/jxb/erac219
PII 6590035
PMID 35595516
PMC PMC9467657
MeSH Bacterial Proteins / genetics Bacterial Proteins / metabolism Nitrate Reductase / genetics Nitrate Reductase / metabolism Nitrates / metabolism Nitrogen / metabolism Synechococcus* / genetics Synechococcus* / metabolism
IF 5.908
Algae NIES-843 NIES-970 NIES-981 NIES-2107 NIES-2134 NIES-2135 NIES-2481 NIES-2549 NIES-3709 NIES-3754 NIES-3756 NIES-3757 NIES-4074 NIES-25 NIES-50 NIES-204 NIES-267