Transcription factor bHLH121 regulates root cortical aerenchyma formation in maize

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 120; no. 12; p. e2219668120
• Main Authors: Schneider, Hannah M., Lor, Vai S., Zhang, Xia, Saengwilai, Patompong, Hanlon, Meredith T., Klein, Stephanie P., Davis, Jayne L., Borkar, Aditi N., Depew, Cody L., Bennett, Malcolm J., Kaeppler, Shawn M., Brown, Kathleen M., Bhosale, Rahul, Lynch, Jonathan P.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 21.03.2023
• Subjects: abiotic stress; aerenchyma; anatomy; BASIC BIOLOGICAL SCIENCES; Biological Sciences; climate; Climate adaptation; Corn; cortex; CRISPR; CRISPR-Cas systems; Crop resilience; Exploration; Gene mapping; genes; Genome-wide association studies; Genome-Wide Association Study; Genomes; Laser ablation; loss-of-function mutation; maize; Mutants; nitrogen; Nucleotides; Nutrient uptake; phenotype; Phenotypes; Phenotyping; Plant Roots - metabolism; Plant tissues; Polymorphism; root; root anatomy; Science & Technology - Other Topics; Single-nucleotide polymorphism; Soil; Soil environment; Soil improvement; Soils; tomography; Transcription factors; Transcription Factors - metabolism; transposons; Water - metabolism; Zea mays - metabolism; cortex; aerenchyma; anatomy; maize; root
• ISSN: 0027-8424; 1091-6490; 1091-6490
• DOI: 10.1073/pnas.2219668120

Root anatomical phenotypes present a promising yet underexploited avenue to deliver major improvements in yield and climate resilience of crops by improving water and nutrient uptake. For instance, the formation of root cortical aerenchyma (RCA) significantly increases soil exploration and resource capture by reducing the metabolic costs of root tissue. A key bottleneck in studying such phenotypes has been the lack of robust high-throughput anatomical phenotyping platforms. We exploited a phenotyping approach based on laser ablation tomography, termed Anatomics , to quantify variation in RCA formation of 436 diverse maize lines in the field. Results revealed a significant and heritable variation for RCA formation. Genome-wide association studies identified a single-nucleotide polymorphism mapping to a root cortex-expressed gene-encoding transcription factor bHLH121. Functional studies identified that the bHLH121 Mu transposon mutant line and CRISPR/Cas9 loss-of-function mutant line showed reduced RCA formation, whereas an overexpression line exhibited significantly greater RCA formation when compared to the wild-type line. Characterization of these lines under suboptimal water and nitrogen availability in multiple soil environments revealed that bHLH121 is required for RCA formation developmentally as well as under studied abiotic stress. Overall functional validation of the bHLH121 gene’s importance in RCA formation provides a functional marker to select varieties with improved soil exploration and thus yield under suboptimal conditions.