Duplicate transcription factorsGT1andVRS1regulate branching and fertile flower number in maize andBrachypodium distachyon

Abstract

Crop engineering and de novo domestication using genome editing are new frontiers in agriculture. However, outside of well-studied crops and model systems, prioritizing engineering targets remains challenging. Evolution can serve as our guide, revealing high-priority genes with deeply conserved roles. Indeed,GRASSY TILLERS1(GT1),SIX-ROWED SPIKE1(VRS1), and their homologs have repeatedly been targets of selection in domestication and evolution. This repeated selection may be because these genes have an ancient, conserved role in regulating growth repression. To test this, we determined the roles ofGT1andVRS1homologs in maize (Zea mays) and the distantly related grass brachypodium (Brachypodium distachyon) using CRISPR-Cas9 gene editing and mutant analysis.GT1andVRS1have roles in floral development in maize and barley, respectively. Grass flowers are borne in branching structures called spikelets. In maize spikelets, carpels are suppressed in half of all initiated ear flowers. These spikelets can only produce single grains. We show thatgt1; vrs1-like1(vrl1) mutants have derepressed carpels in ear flowers. Importantly, these plants can produce two grains per spikelet. In brachypodium,bdgt1; bdvrl1mutants have more branches, spikelets, and flowers than wildtype plants, indicating conserved roles forGT1andVRS1homologs in growth suppression. Indeed, maizeGT1can suppress growth inArabidopsis thaliana, separated from the grasses by ca. 160 million years of evolution. Thus,GT1andVRS1maintain their potency as growth regulators across vast timescales and in distinct developmental contexts. Modulating the activity of these and other conserved genes may be critical in crop engineering.

Multilayered regulation of developmentally programmed pre-anthesis tip degeneration of the barley inflorescence

“…7 ). This result supports the evolutionarily conserved function of HD-ZIP class I family members in growth repression, as observed in grasses and eudicots ( Komatsuda et al 2007 ; Whipple et al 2011 ; González-Grandío et al 2017 ; Sakuma et al 2017 ; Gallagher et al 2023 ). The maize ortholog GT1 is an essential domestication gene that suppresses carpel development in tassel florets and elongation of lateral ear branches and promotes axillary bud dormancy putatively regulated by the other domestication gene TB1 , encoding a TCP TF ( Dong et al 2019 ; Klein et al 2022 ; Whipple et al 2011 ).…”