Systemic Signaling of the Plant Nitrogen Status Triggers Specific Transcriptome Responses Depending on the Nitrogen Source in Medicago truncatula
- 20 February 2008
- journal article
- Published by Oxford University Press (OUP) in Plant Physiology
- Vol. 146 (4), 2020-2035
- https://doi.org/10.1104/pp.107.115667
Abstract
Legumes can acquire nitrogen (N) from NO3 −, NH4 +, and N2 (through symbiosis with Rhizobium bacteria); however, the mechanisms by which uptake and assimilation of these N forms are coordinately regulated to match the N demand of the plant are currently unknown. Here, we find by use of the split-root approach in Medicago truncatula plants that NO3 − uptake, NH4 + uptake, and N2 fixation are under general control by systemic signaling of plant N status. Indeed, irrespective of the nature of the N source, N acquisition by one side of the root system is repressed by high N supply to the other side. Transcriptome analysis facilitated the identification of over 3,000 genes that were regulated by systemic signaling of the plant N status. However, detailed scrutiny of the data revealed that the observation of differential gene expression was highly dependent on the N source. Localized N starvation results, in the unstarved roots of the same plant, in a strong compensatory up-regulation of NO3 − uptake but not of either NH4 + uptake or N2 fixation. This indicates that the three N acquisition pathways do not always respond similarly to a change in plant N status. When taken together, these data indicate that although systemic signals of N status control root N acquisition, the regulatory gene networks targeted by these signals, as well as the functional response of the N acquisition systems, are predominantly determined by the nature of the N source.Keywords
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