The B1–TaHDA6 module negatively regulates root hair length through reactive oxygen species homeostasis in wheat

Abstract Root hairs serve as a crucial interface between plants and soil, facilitating efficient water and nutrient uptake. However, the genetic mechanisms governing root hair traits in wheat (Triticum aestivum L.) remain largely unexplored. In this study, we identified the awn inhibitor gene B1 as an important regulator of root hair length (RHL) through map-based cloning and reported a preferred allele for an ideotype of the root system in wheat. B1 suppressed RHL by decreasing reactive oxygen species (ROS) buildup, whereas a defective B1 resulted in increased RHL and enhanced nutrient uptake efficiency in wheat. In addition, B1 directly repressed the expression of ROOT HAIR DEFECTIVE SIX-LIKE2 (TaRSL2) and ROOT HAIR DEFECTIVE SIX-LIKE4 (TaRSL4), encoding two positive regulators of RHL, thereby activating TaRBOHH9 expression and accelerating ROS production. Furthermore, B1 interacted with TaHDA6, reducing histone H3K9ac and H3K14ac modifications and inhibiting the expression of downstream genes. Our work not only unveils the pivotal role of B1-mediated epigenetic regulation of RHL and nutrient uptake, but also presents editable molecular targets for breeding eco-friendly sustainable crops.