Diverse phosphate and auxin transport loci distinguish phosphate tolerant from sensitive Arabidopsis accessions
journal contributionposted on 2021-11-08, 22:51 authored by Changyu YiChangyu Yi, Xinchao Wang, Qian Chen, Damien L Callahan, Alexandre Fournier-Level, James WhelanJames Whelan, Ricarda JostRicarda Jost
Phosphorus is an essential element for plant growth often limiting agroecosystems. To identify genetic determinants of performance under variable phosphate supply, we conducted genome-wide-association studies on five highly predictive phosphate starvation response traits in 200 Arabidopsis (Arabidopsis thaliana) accessions. Phosphate concentration in phosphate-limited organs had the strongest, and primary root length had the weakest genetic component. Of 70 trait-associated candidate genes, 17 responded to phosphate withdrawal. The PHOSPHATE TRANSPORTER1 gene cluster on chromosome 5 comprised PHT1;1, PHT1;2 and PHT1;3 with known impact on phosphorus status. A second locus featured uncharacterized endomembrane-associated auxin efflux carrier encoding PIN-LIKES7 (PILS7) which was more strongly suppressed in phosphate-limited roots of phosphate-starvation sensitive accessions. In the Col-0 background, phosphate uptake and organ growth were impaired in both phosphate-limited pht1;1 and two pils7 T-DNA insertion mutants, while phosphate-limited pht1;2 had higher biomass and pht1;3 was indistinguishable from wild type. Copy number variation at the PHT1 locus with loss of the PHT1;3 gene and smaller scale deletions in PHT1;1 and PHT1;2 predicted to alter both protein structure and function suggest diversification of PHT1 is a key driver for adaptation to phosphorus limitation. Haplogroup analysis revealed a phosphorylation site in the protein encoded by the PILS7 allele from stress-sensitive accessions as well as additional auxin-responsive elements in the promoter of the ‘stress tolerant’ allele. The former allele’s inability to complement the pils7-1 mutant in the Col-0 background implies the presence of a kinase signaling loop controlling PILS7 activity in accessions from phosphorus-rich environments, while survival in phosphorus-poor environments requires fine-tuning of stress-responsive root auxin signaling.