Plasticity Regulators Modulate Specific Root Traits in Discrete Nitrogen Environments

Abstract

Plant development is remarkably plastic but how precisely can the plant customize its form to specific environments? When the plant adjusts its development to different environments, related traits can change in a coordinated fashion, such that two traits co-vary across many genotypes. Alternatively, traits can vary independently, such that a change in one trait has little predictive value for the change in a second trait. To characterize such “tunability” in developmental plasticity, we carried out a detailed phenotypic characterization of complex root traits among 96 accessions of the model Arabidopsis thaliana in two nitrogen environments. The results revealed a surprising level of independence in the control of traits to environment – a highly tunable form of plasticity. We mapped genetic architecture of plasticity using genome-wide association studies and further used gene expression analysis to narrow down gene candidates in mapped regions. Mutants in genes implicated by association and expression analysis showed precise defects in the predicted traits in the predicted environment, corroborating the independent control of plasticity traits. The overall results suggest that there is a pool of genetic variability in plants that controls traits in specific environments, with opportunity to tune crop plants to a given environment.

Auxin and Strigolactone Signaling Are Required for Modulation of Arabidopsis Shoot Branching by Nitrogen Supply

“…To date, four such genes are known: MAX1, MAX3, MAX4, and DWARF27. Among six experiments examining the effects of NO 3 2 supply or resupply after NO 3 2 deprivation (Wang et al, 2003;Scheible et al, 2004;Gifford et al, 2008Gifford et al, , 2013Patterson et al, 2010;Krapp et al, 2011), we found no evidence of a consistent effect of N supply on the transcription of any of these genes (Supplemental Table S1). The transcript abundance of core genes in the SL signaling pathway, DWARF14 and MAX2, was also not affected (Supplemental Table S1).…”

Changes in Gene Expression in Space and Time Orchestrate Environmentally Mediated Shaping of Root Architecture

“…Furthermore, networks can identify control hubs and enable prediction of the effect of genetic perturbations . In the case of root environmental responses, nitrogen responses have been studied at the whole root level over the first minutes of nitrate influx at 2 h in isolated root cell types (Gifford et al, 2008) and at the phenotypic level to look at longer-term effects of nitrogen on root development (Gifford et al, 2013). A number of previous network inference studies have investigated the response of Arabidopsis thaliana to nitrogen and have helped to identify major nitrogen-responsive sensors and hubs.…”

Environmental nitrate signals through abscisic acid in the root tip

“…[1][2][3][4][5] For plants that do not form a nitrogenfixing symbiosis, nitrate is a major source of nitrogen nutrition, and thus nitrate sensing and response is a core signaling module that intersects with many hormone signaling pathways, especially that of auxin, cytokinin and gibberellin. 6,7 More recently, the intersection of nitrate signaling with abscisic acid signaling has begun to be resolved.…”