A Trypsin Family Protein Gene Controls Tillering and Leaf Shape in Barley.

Tillering or branching is an important agronomic trait in plants, especially cereal crops. Previously, in barley () 'Vlamingh', we identified the () mutant from a γ-ray-treated segregating population. exhibited more tillers per plant, narrower leaves, and reduced plant height compared with the wild-type parent. In this study, we show that the increased tiller number per plant is caused by accelerated outgrowth of tiller buds and that narrower leaves are caused by a reduction in vascular tissue and cell number. Genetic analysis revealed that a 2-bp deletion in the gene (), encoding a trypsin family protein, was responsible for the mutant phenotype. Gene function was further confirmed by transgenic complementation with and RNA interference experiments. was expressed in vascular tissue, leaf axils, and adventitious root primordia and shown to negatively regulate tiller development. Mutation of led to the accumulation of a putative cyclophilin-type peptidyl-prolyl cis/trans-isomerase (HvPPIase), which physically interacts with the HvHNT1 protein in the nucleus of plant cells. Our data suggest that controls tiller development and leaf width through , thus contributing to understanding of the molecular players that control tillering in barley.