Molecular characterization of wheat floret development‐related F‐box protein (TaF‐box2): Possible involvement in regulation of Arabidopsis flowering

Abstract In wheat ( Triticum aestivum L.), the floret development stage is an important step in determining grain yield per spike; however, the molecular mechanisms underlying floret development remain unclear. In this study, we elucidated the role of TaF‐box2, a member of the F‐box‐containing E3 ubiquitin protein ligases, which is involved in floret development and anthesis of wheat. TaF‐box2 was transiently expressed in the plasma membrane and cytoplasm of both tobacco and wheat. We also found that the SCF F‐box2 (Skp1‐Cul1‐Rbx1‐TaF‐box2) ubiquitin ligase complex mediated self‐ubiquitination activity. Transgenic Arabidopsis plants that constitutively overexpressed TaF‐box2 showed markedly greater hypocotyl and root length than wild‐type plants, and produced early flowering phenotypes. Flowering‐related genes were significantly upregulated in TaF‐box2 ‐overexpressing Arabidopsis plants. Further protein interaction analyses such as yeast two‐hybrid, in vitro pull‐down, and bimolecular fluorescence complementation assays confirmed that TaF‐box2 physically interacted with TaCYCL1 ( Triticum aestivum cyclin‐L1‐1). Ubiquitination and degradation assays demonstrated that TaCYCL1 was ubiquitinated by SCF F‐box2 and degraded through the 26S proteasome complex. The physiological functions of the TaF‐box2 protein remain unclear; however, we discuss several potential routes of involvement in various physiological mechanisms which counteract flowering in transgenic Arabidopsis plants.