PIF4-controlled auxin pathway contributes to hybrid vigor in Arabidopsis thaliana

Hybrid vigor is a well-known but still poorly understood phenomenon in which the F1 hybrid progeny of a cross often show enhanced growth as compared to either parent. True-breeding lines that retain this enhanced growth, known as hybrid mimics, have been developed and are important tools for understanding hybrid vigor. Wang et al. characterized several hybrid mimic lines as well as true-breeding lines with a medium (parental-like) or small phenotype. They identified several chromosomal regions and differentially-expressed genes associated with the large or small phenotype. One of the differentially expressed genes associated with larger size, PIF4, encodes a transcription factor that contributes to auxin synthesis, which may contribute directly to the larger size of the hybrid mimics. Proc. Natl. Acad. Sci. USA 10.1073/pnas.1703179114