A La-Related Protein LaRP6a Delays Flowering of Arabidopsis thaliana by Upregulating FLC Transcript Levels

Abstract

La-related proteins (LaRPs) are RNA-binding proteins (RBPs) that contain a La-type helix-turn-helix (HTH) domain and are found in all eukaryotes, including plants, animals, and yeasts. Although the functions of a few LaRPs have been determined during plant growth and development, the roles of most LaRPs in plants remain unknown. Here, the function of an Arabidopsis thaliana LaRP6a (At5g46250) harboring a La-type HTH domain and an RNA-recognition motif was determined in the growth and development of Arabidopsis. Confocal analysis of subcellular localization of the LaRP6a–GFP fusion protein revealed that LaRP6a protein is localized to both the nucleus and plasma membrane. Overexpression of LaRP6a resulted in delayed flowering and increased plant height and seed yield. The transcript level of the floral repressor FLC was markedly increased in LaRP6a-overexpressing transgenic plants. LaRP6a protein bound to the 3ʹUTR of the FLC transcript and possessed RNA chaperone activity. Collectively, these results suggest that LaRP6a plays a role in the control of flowering time by regulating FLC transcript levels.