Yasuo Hotta

Glycine-rich proteins: a class of novel proteins.

Glycine-rich proteins (GRPs) containing more than 60% glycine have been found in different tissues from many eukaryotic species. Despite the availability of literature on different groups of GRPs, there are few reports in which they are all considered and compared together. Some of these proteins are components of the cell walls of many higher plants. In most cases, it has been shown that they are accumulated in the vascular tissues and that their synthesis is part of the plant’s defense mechanism. Other distinct types of GRPs are characterized by having structures and functions similar to animal cytokeratins or by a domain with typical RNA-binding motifs. The availability of cloned GRP genes facilitates the study of the function of this diverse class of proteins, which is expected to enhance the understanding of cell physiology.

Dmc1 fluorescent foci in prophase I nuclei of diploid, triploid and hybrid lilies

Abstract. We examined the distribution of meiotic epitopes for the Dmc1 protein of lilies in a normal diploid, a triploid, and in a diploid species-hybrid. The triploid has an extra chromosome set; all three sets align, but only two of the three axes intimately pair at a given location. Our findings with the triploid support the idea that retention of the foci until the pachytene stage requires a successful homology check and synaptonemal complex (SC) initiation; the number of foci in the triploid diminishes by approximately 30% from early zygotene to pachytene, and the triploid pachytene values are similar to the pachytene values of the diploid. The species-hybrid lacks chromosome homology, has reduced SC formation and few reciprocal genetic exchanges. In this species-hybrid the number of foci at early zygotene is similar to that in the normal diploid but is dramatically reduced by mid-zygotene. The extent to which the number of Dmc1 foci is reduced is similar to the extent that SC formation is reduced. In contrast the extent of the reduction in reciprocal genetic exchange in the species-hybrid is much greater than the reduction in the number of foci. We conclude that Dmc1 protein is involved in homology checking, but the impact of failure to find homology affects SC formation and reciprocal genetic exchange differentially.

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

Abstract 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.