Phosphate transporter PHT1;1 as a key determinant of phosphorus acquisition in Arabidopsis natural accessions
To understand the genetic basis in governing phosphorus (P) acquisition, we performed genome-wide association studies (GWAS) on a diversity panel of Arabidopsis thaliana by two primary determinants of P acquisition, phosphate (Pi)-uptake activity and PHOSPHATE TRANSPORTER 1 (PHT1) protein abundance. Association mapping revealed a shared significant peak on chromosome 5 (Chr5) where the PHT1;1/2/3 genes reside, suggesting a strong correlation between the regulation of Pi-uptake activity and PHT1 protein abundance. Genes encoding transcription factors, kinases, and a metalloprotease associated with both traits were also identified. Conditional GWAS followed by statistical analysis of genotype-dependent expression of PHT1;1 and transcription activity assays revealed an epistatic interaction between PHT1;1 and MYB DOMAIN PROTEIN 52 (MYB52) on Chr1. Analyses of F1 hybrids generated by crossing two subgroups of natural accessions carrying specific SNPs associated with PHT1;1 and MYB52 further revealed the strong effects of potential variants on PHT1;1 expression and Pi uptake activity. Notably, the soil P contents in A. thaliana habitats were found to coincide with PHT1;1 haplotype, underscoring how fine-tuning of the activity of P acquisition by natural variants allows plants to adapt to their environments. This study sheds light on the complex regulation of P acquisition and offers a framework to systematically assess the effectiveness of GWAS approaches in the study of quantitative traits.