Gene editing of the wheat homologs of TONNEAU1-recruiting motif encoding gene affects grain shape and weight in wheat

Authors: WANG, WEI - Kansas State University; PAN, QUANLI - Kansas State University; TIAN, BIN - Kansas State University; HE, FEI - Kansas State University; CHEN, YUEYING - Kansas State University; AKHUNOVA, ALINA - Kansas State University; Bai, Guihua; TRICK, HAROLD - Kansas State University; AKHUNOV, EDUARD - Kansas State University

Submitted to: Plant Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/10/2019
Publication Date: 6/20/2019
Citation: Wang, W., Pan, Q., Tian, B., He, F., Chen, Y., Akhunova, A., Bai, G., Trick, H., Akhunov, E. 2019. Gene editing of the wheat homologs of TONNEAU1-recruiting motif encoding gene affects grain shape and weight in wheat. Plant Journal. https://doi.org/10.1111/tpj.14440.
DOI: https://doi.org/10.1111/tpj.14440

Interpretive Summary: Grain size and weight are two important wheat yield components. Using gene editing, we demonstrated that the TaGW7 gene regulates wheat grain size and weight. The strength of effects of genes in different wheat subgenomes (A, B or D) correlated with the levels of their expression. TaGW7 is involved in the pathways regulating cell division and organ growth and likely played an important role in the evolution of yield traits in cultivated wheat. This new knowledge may lead to improved versions of TaGW7 for improving grain size and weight.

Technical Abstract: Grain size and weight are important components of a suite of yield-related traits in crops. Here, we showed that the CRISPR-Cas9 gene editing of TaGW7, a homolog of rice OsGW7 encoding a TONNEAU1-recruiting motif (TRM) protein, affects grain shape and weight in allohexaploid wheat. By editing the TaGW7 homoeologs in the B and D genomes, we showed that mutations in either of the two or both genomes increased the grain width and weight but reduced the grain length. The effect sizes of mutations in the TaGW7 gene homoeologs coincided with the relative levels of their expression in the B and D genomes. The effects of gene editing on grain morphology and weight traits were dosage dependent with the double-copy mutant showing larger effect than the respective single copy mutants. The TaGW7-centered gene co-expression network indicated that this gene is involved in the pathways regulating cell division and organ growth, also confirmed by the cellular co-localization of TaGW7 with a- and b-tubulin proteins, the building blocks of microtubule arrays. The analyses of exome capture data in tetraploid domesticated and wild emmer, and hexaploid wheat revealed the loss of diversity around TaGW7-associated with domestication selection, suggesting that TaGW7 is likely to play an important role in the evolution of yield component traits in wheat. Our study showed how integrating CRISPR-Cas9 system with cross-species comparison can help to uncover the function of a gene fixed in wheat for allelic variants targeted by domestication selection and select targets for engineering new gene variants for crop improvement.