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Summary: Tillering is an important parameter of plant architecture in cereal crops. In this study, we identified the PHYTOCHROME‐INTERACTING FACTOR‐LIKE (PIL) family transcription factors as new repressors of tillering in cereal crops.Using biochemical and genetic approaches, we explore the roles of TaPIL1 in regulating wheat plant architecture. We found that the PIL protein TaPIL1 controls tiller number in wheat.Overexpression of TaPIL1 reduces wheat tiller number; additionally, overexpression of TaPIL1‐SUPERMAN repression domain increases wheat tiller number. Furthermore, we show that TaPIL1 activates the transcriptional expression of wheat TEOSINTE BRANCHED1 (TaTB1); moreover, TaPIL1 physically interacts with wheat SQUAMOSA PROMOTER BINDING PROTEIN‐LIKE (TaSPL)3/17, which are activators of TaTB1 transcription. In rice, overexpression and loss‐of‐function mutations of OsPIL11 reduce or increase tiller number by regulating the expression of OsTB1. In Arabidopsis, we demonstrate that PHYTOCHROME‐INTERACTING FACTOR 4 interacts with SPL9 to inhibit shoot branching.This study reveals that PIL family transcription factors directly interact with SPLs and play an important role in repressing tillering/branching in plants. [ABSTRACT FROM AUTHOR]

Summary: The domestication gene Q is largely responsible for the widespread cultivation of wheat because it confers multiple domestication traits. However, the underlying molecular mechanisms of how Q regulates these domestication traits remain unclear.In this study, we identify a Q‐interacting protein TaLAX1, a basic helix–loop–helix transcription factor, through yeast two‐hybrid assays. Using biochemical and genetic approaches, we explore the roles of TaLAX1 in regulating wheat domestication traits.Overexpression of TaLAX1 produces phenotypes, reminiscent of the q allele; loss‐of‐function Talax1 mutations confer compact spikes, largely similar to the Q‐overexpression wheat lines. The two transcription factors TaLAX1 and Q disturb each other's activity to antagonistically regulate the expression of the lignin biosynthesis‐related gene TaKNAT7‐4D. More interestingly, a natural variation (InDel, +/− TATA), which occurs in the promoter of TaLAX1, is associated with the promoter activity difference between the D subgenome of bread wheat and its ancestor Aegilops tauschii accession T093.This study reveals that the transcription factor TaLAX1 physically interacts with Q to antagonistically regulate wheat domestication traits and a natural variation (InDel, +/− TATA) is associated with the diversification of TaLAX1 promoter activity. [ABSTRACT FROM AUTHOR]