The interaction of Carbon and Nitrogen signalling within Arabidopsis thaliana and the effect on root foraging response phenotypes.

Abstract

Plants are sessile and must display phenotypic plasticity to adapt to specific environmental conditions. This includes the well-studied root foraging response in Arabidopsis thaliana which induces lateral root growth in response to a shortage of nitrogen during growth. This report studied this response in a more complex environment where varying amounts of sucrose and nitrate are supplied through growth media to study biomass investment decisions within A. thaliana. Within varying C/N balances, an interaction phenotype was observed, where sucrose induces more root system architecture (RSA) growth in high nitrate-grown plants than low nitrate-grown plants, even though low nitrate plants display the expected foraging response even within low sucrose. It was then investigated how this phenotype reflects upon auxin and cytokinin accumulation amounts in the main root of treated plants. It was found that both auxin and cytokinin accumulate within high nitrogen-grown plants independently of sucrose conditions wherein plants were grown. Lastly, an NRT1.1 mutant which was theorized to affect the phenotype observed was subjected to similar C/N balance conditions. However, the results of the experiment could not be reliably quantified due to plant growth during this experiment being largely affected by an unknown factor. Ultimately, it is theorized that the observed interaction phenotype is mediated through various signalling cascades regulated by the SnRK1/TOR, NRT1.1, NLP7, PINs and AUX1/LAX complexes intersecting with one another, which results in highly adaptable changes to the RSA.