Developmental gene expression in Gaspe in response to nitrate. Zea mays

Elucidation of the gene networks underlying the response to N supply and demand should facilitate the improvement of the N uptake efficiency of plants. We undertook a transcriptomic analysis of maize to identify genes responding to both NO3- provision and to development-based N demand changes across the entire lifecycle. Gene co-expression networks were derived by cluster analysis of the transcript profiles. The majority of NO3--responsive transcription occurred at 11 (D11), 18 (D18) and 29 (D29) days after emergence, with differential expression predominating in the root at D11 and D29 and in the leaf at D18. A cluster of 98 probe sets was identified, the expression pattern of which is similar to that of the high-affinity NO3- transporter (NRT2) genes across the lifecycle. The cluster is enriched with genes encoding enzymes and proteins of lipid metabolism and transport, respectively. These are candidate genes for the response of maize to N supply and demand. Only a few patterns of differential gene expression were observed over the entire lifecycle, however the composition of the classes of the genes differentially regulated at individual time points was unique, suggesting tightly controlled regulation of NO3- responsive gene expression. Overall design: Gaspe Flint maize was grown hydroponically for the entire lifecycle on 0.5 or 2.5 mM NO3-. Shoot and root tissues were harvested from three biological replicates at seven time points during the lifecycle, RNA was extracted, fluorescently labled cRNA was synthesised and hybridised to a 4x44K microarray.