The auxin efflux carrier PIN1a regulates vascular patterning in cereal roots

• DOI: 10.1111/nph.19777
• Publication Date: 2024-04-26T08:29:42Z
• Authors: Riccardo Fusi; Sara Giulia Milner; Serena Rosignoli; Riccardo Bovina; Cristovão De Jesu...; Haoyu Lou; Brian S. Atkinson; Aditi N. Borkar; Larry M. York; Dylan H. Jones; Craig J. Sturrock; Nils Stein; Martin Mascher; Roberto Tuberosa; Devin O'Connor; Malcolm J. Bennett; Anthony Bishopp; Silvio Salvi; Rahul Bhosale
• Keywords: 580; 570; auxin efflux carrier; Indoleacetic Acids; Meristem; Cereals; barley; Membrane Transport Proteins; Hordeum; root; Genes, Plant; Plant Roots; vascular development; PIN1; auxin efflux carrier; barley; root; vascular development; auxin efflux carrier ; PIN1 ; root ; barley ; vascular development; PIN1; Phenotype; Gene Expression Regulation, Plant; Mutation; Plant Vascular Bundle; Edible Grain; Alleles; Plant Proteins; Brachypodium; Body Patterning

Summary

Barley (Hordeum vulgare) is an important global cereal crop and a model in genetic studies. Despite advances in characterising barley genomic resources, few mutant studies have identified genes controlling root architecture and anatomy, which plays a critical role in capturing soil resources. Our phenotypic screening of a TILLING mutant collection identified line TM5992 exhibiting a short‐root phenotype compared with wild‐type (WT) Morex background. Outcrossing TM5992 with barley variety Proctor and subsequent SNP array‐based bulk segregant analysis, fine mapped the mutation to a cM scale. Exome sequencing pinpointed a mutation in the candidate gene HvPIN1a, further confirming this by analysing independent mutant alleles. Detailed analysis of root growth and anatomy in Hvpin1a mutant alleles exhibited a slower growth rate, shorter apical meristem and striking vascular patterning defects compared to WT. Expression and mutant analyses of PIN1 members in the closely related cereal brachypodium (Brachypodium distachyon) revealed that BdPIN1a and BdPIN1b were redundantly expressed in root vascular tissues but only Bdpin1a mutant allele displayed root vascular defects similar to Hvpin1a. We conclude that barley PIN1 genes have sub‐functionalised in cereals, compared to Arabidopsis (Arabidopsis thaliana), where PIN1a sequences control root vascular patterning.