Mutational analysis of the signal for a nuclear localization of proteins which accumulate specifically during meiosis in lily microsporocytes

LIM5 and LIM13 are novel meiosis-associated genes isolated from Lilium Long iflorum. The presence of a hydrophobic N-terminal region predicted from the amino acid sequence has suggested that they function as extracellular stru ctural components. However, both proteins also contain clusters of basic am ino acids which may function as nuclear localization signals. To investigat e the cellular localization of the protein, we tagged the C-termini of LIMS and LIM13 with a green fluorescent protein. Transient expression of fusion proteins in onion epidermal cells revealed nuclear localization activity o f both proteins. Mutational analysis indicated that amino acid sequences th at constitute bipartite-type nuclear localization signals are necessary and sufficient for the intracellular localization of both proteins.