ABSTRACTcDNA clones encoding proteins of -18 kDa in which 83% of the amino acids are conserved relative to the published sequences of mammalian cyclophilin/rotamase (CyP) have been isolated from tomato, maize, and Brassica napus. In correspondence with the mammalian genes, but in contrast with the Neurospora gene and one yeast CyP gene, the plant CyP genes encode only mature proteins lacking transit peptides. RNA blot analyses demonstrate that CyP genes are expressed in all plant organs tested. Southern blots of genomic DNA indicate that there are small families (two to eight members) of CyP-related genes in maize and B. napus. A vector was constructed for expression of the tomato cDNA in E. coil. SDS/polyacrylamide gels show that extracts of appropriately induced cells harboring this vector contain nearly 40% of the protein as a single "18-kDa band. While the majority of this protein is sequestered in insoluble inclusion bodies, the soluble extracts have higher levels of peptidyl-prolyl cis-trans isomerase (rotamase) activity than extracts of wild-type cells. This additional activity is sensitive to inhibition by the cyclic undecapeptide cyciosporin A.

We have characterized a gene, 9612, that is expressed predominantly in the styles of tomato pistils according to a tightly regulated temporal program. 9612 RNA levels were maximal in mature pistils from flowers at anthesis, with transcripts undetectable in pistils from flowers collected 5-7 days prior to anthesis. In situ localization of mRNA in tissue sections showed that expression of the gene is confined in the pistil to the outer five cell layers of the strands of transmitting tissue within the upper two-thirds of the style. The maximal levels of 9612 RNA detected in anthers and vegetative organs were more than 50-fold and 250-fold lower than the level in pistils, respectively. A homolog to the 9612 gene was detected in tobacco and was also found to be expressed predominantly in the style. The ability of the 5' flanking region of the tomato gene to appropriately regulate expression of a heterologous coding sequence was examined in transformed tomato and tobacco plants. In contrast to results with previously described regulated genes, the 9612 promoter functions correctly in the pistils of tomato plants, but fails to direct correct expression in tobacco plants. The sequence of the 9612 cDNA includes an open reading frame encoding a polypeptide of 404 amino acids with a highly hydrophobic amino-terminal region that may represent a signal peptide.

We have used a differential plaque hybridization screening procedure to isolate cDNA clones for genes that show elevated or exclusive expression in tomato pistils. Clones that showed maximal expression in immature pistils (premeiotic to early meiosis) and mature pistils (at anthesis) were isolated. Of nine clones that were characterized, four were found also to express at some stage of anther development. In situ hybridization experiments showed that expression of the genes we have identified is very tightly regulated both spatially and temporally within the pistil. One gene was identified that is expressed in the pistil only in the transmitting tissue of the style. A second gene was found to express exclusively in two to three cell layers of the ovules for a period of less than eight days.

The sequences of both the gene and the corresponding protein of adenovirus major core protein VII have been determined. The precise location of this gene is between 43.37 and 44.90 map coordinates on the viral genome. Protein VII is 173 residues long and has a molecular weight of 19,258. Detailed analysis of its sequence has revealed four basic domains separated by several predicted a helices. It is proposed that intrachain folding of protein VII is driven by hydrophobic interactions of the a helices, leaving the basic domains of the protein to interact with DNA phosphates. Protein monomers may further associate with each other in the formation of hexameric nucleosome-like particles. The displacement and replacement of protein VII during the viral infectious cycle in the host cell appears to mimic the biology of nucleoprotamine during the processes of spermatogenesis and fertilization. The presence of a protamine-like domain affirms a hybrid histone/protamine molecular structure for protein VII, although it may resemble the protamine in function.DNA is associated with various classes of basic proteins in the nuclei of eukaryotic cells. These proteins provide structural stability as well as functional organization of the DNA into chromosomes. As an example of the different and specific roles of the nuclear proteins, full complements of somatic histones in genetically active germ-line cells are progressively replaced by the arginine-rich protamine of mature sperm (1). During the process of fertilization, protamine is removed, histones regain their associations with the DNA, and the compact chromatin of the sperm decondenses. The "life cycles" of the two classes of basic proteins in relation to the life cycle of sperm cells indicate their distinctive interactions with DNA. Among the histones, additional distinctions can be made for their role in the structure and expression of genomic DNA.The core histones, H2a, H2b, H3, and H4, are functionally different from the spacer histone, H1 (2). Because There are 1,080 copies of core protein VII (Mr = 18,000) and 180 copies of the minor core protein V (Mr = 45,000) involved in the formation of the compact virus core (6). Micrococcal nuclease digestion of the virus core has resulted in a 150-base-pair subunit DNA fragment (7), but no nucleosome repeat pattern has been observed. As early as 3 hr after infection, intranuclear adenovirus DNA assumes a nucleosomal repeat pattern similar to that of cellular chromatin (8-11). This suggests that, during virus uncoating to produce transcriptionally active viral DNA, the adenovirus 2 specific basic proteins VII and V are replaced by histones. Viral DNA synthesis, which begins at 6 hr after infection, initiates the transcription of late genes coding for viral structural polypeptides. At the late stage of infection, progeny viral DNA once again assumes the viral chromatin structure (10). The replacement of basic nuclear proteins during the growth and development of the adenovirion appears to mimic the life cycle of histones...

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We have used a differential plaque hybridization screening procedure to isolate eDNA clones for genes that show elevated or exclusive expression in tomato pistils. Clones that showed maximal expression in immature pistils (premeiotic to early meiosis) and mature pistils (at anthesis) were isolated. Of nine clones that were characterized, four were found also to express at some stage of anther development. In situ hybridization experiments showed that expression of the genes we have identified is very tightly regulated both spatially and temporally within the pistil. One gene was identified that is expressed in the pistil only in the transmitting tissue of the style. A second gene was found to express exclusively in two to three cell layers of the ovules for a period of less than eight days. INTRODUCTIONAlthough the development of a higher plant is responsive to environmental influences, the heritability of form and function in plants demonstrates that this process is primarily under genetic control. The organ-specific modulation of gene expression is necessarily responsible for the biochemical differentiation of the cells within an organ or tissue. Kamalay and Goldberg (1980) have shown that each plant organ contains numerous transcripts that are not present in other plant organs. Identification of the regulated genes and determination of the functions of their protein products are important steps in the formation of a complete model of plant development. Recent publications have reported the isolation of a number of organ-specific sequences from stems, petals, roots, and floral organs of tobacco (Goidberg, 1988), embryos of soybean (Goldberg, 1988), germinating embryos of Brassica napus (Harada et al., 1988), and various organs of Arabidopsis thaliana (Simoens et al., 1988).We have chosen the process of floral differentiation as a model for studies on developmentally regulated plant genes. Flowering is a complex process that typifies essentially all of the major aspects of plant development: organogenesis, differential cell division, cellular differentiation, and alterations in gene expression. Flowering begins with a series of events that lead to the conversion of a vegetative meristem to a floral meristem. This conversion is followed by a shift in phyllotaxis and the development of the lateral floral organs: the sepals, petals, stamens, and carpels. As these organs differentiate, a number of spe-1 To whom correspondence should be addressed. 2 Current address: Department of Horticultural Science and Landscape Architecture, University of Minnesota, 305 Alderman Hall, 1970 Folwell Avenue, St. Paul, MN 55108. cialized tissues and structures are produced. These include the carpel walls, the placenta, the transmitting tissue of the style, the stigma, the ovules, the anther walls, the tapetal cells within the anthers, and the micro-and megagametophytes. Each of these tissues contains novel substances that are not found in other plant organs. These substances are the direct or secondary products of floral specifi...

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