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 longiflorum. The presence of a hydrophobic N-terminal region predicted from the amino acid sequence has suggested that they function as extracellular structural components. However, both proteins also contain clusters of basic amino acids which may function as nuclear localization signals. To investigate the cellular localization of the protein, we tagged the C-termini of LIM5 and LIM13 with a green fluorescent protein. Transient expression of fusion proteins in onion epidermal cells revealed nuclear localization activity of both proteins. Mutational analysis indicated that amino acid sequences that constitute bipartite-type nuclear localization signals are necessary and sufficient for the intracellular localization of both proteins. Received: 9 February 1998 / Revision received: 9 March 1999 / Accepted: 22 March 1999