Overexpression of LOV KELCH PROTEIN 2 enhances cell elongation and increases cell number and ploidy in the hypocotyl of Arabidopsis thaliana

Abstract

LOV KELCH PROTEIN 2 (LKP2) belongs to a group of blue light receptors in Arabidopsis thaliana that possess 1 light, oxygen, or voltage (LOV) domain, 1 F-box motif, and 1 kelch repeat domain. Members of this group regulate both the circadian clock and photoperiodic flowering. Transgenic Arabidopsis plants overexpressing a fusion of the genes for green fluorescent protein (GFP) and LKP2 exhibited long hypocotyls and arrhythmicity under constant light and late flowering under long-day conditions, as previously reported for LKP2-overexpressing Arabidopsis plants. The GFP- LKP2-overexpressing plants with elongated hypocotyls had more cortical cells than control plants but the same number of epidermal cells. Further, the cells in the hypocotyls of GFP-LKP2-overexpressing plants, especially in the middle regions of the epidermis and cortex, were longer and possessed larger nuclei, with increased DNA content. Therefore, LKP2 overexpression induces cell elongation and increases in cell number and ploidy in the Arabidopsis hypocotyls.