Gene Type And Mutation Position Influence Responses In Root Traits Across Nutrient Environments

Premise of research. Root traits are influenced by a large number of genes, many of which are environmentally sensitive. Despite a growing body of knowledge on root architecture, we have limited understanding of how mutations in genes affecting root traits at the seedling stage influence root traits and performance of ruderal species across nutrient soil environments at mature plant stages. We tested whether insertion mutants (knockouts) in distinct gene types or the position of the mutation within the gene (exon, promoter) differentially influenced root and shoot architecture and size phenotypes. Methodology. Following synthesis of the literature and publicly available expression data sets for Arabidopsis thaliana, we examined knockouts in three categories of genes: genes with previous evidence of influence on root phenotype, genes with previous evidence of influence on root-shoot interactions, and genes with previously no evidence of root function (PNERFs). Using 97 confirmed-homozygous single-insert Salk T-DNA lines with insertion mutations in either the exon or the promoter, we examined how mutation affected root phenotypes. We grew mutant lines, wild-type Col-0 (also known as Columbia), and 10 natural accessions across three nutrient treatments. We phenotyped plants for above- and belowground traits at maturity. Pivotal results. We detected significant phenotypic plasticity for root phenotypes at the adult stage across mutant gene types. Gene types differed in mean performance and trait relationships. Consistent with our prediction, we found that root gene exon mutants respond substantially across environments. A higher proportion of mutant lines outperformed wild-type Col-0 than underperformed, yet this proportion varied by trait and treatment. Conclusions. These data support the ideas that mutational effects are dependent on environmental conditions and that mutations increase or decrease function in stressful low-nutrient environments. Screens at adult life stages uncover new mutant effects for root phenotypes and fruit production.