Two genes, secE and nusG, situated between the tuJR and ribosomal protein rplKAJL operons in the rif region at 90 min on the Escherichia coli chromosome, have been sequenced and characterized. The secE gene encodes a 127-amino-acid-long polypeptide, which is an integral membrane protein essential for protein export (P. J. Schatz, P. D. Riggs, A. Jacq, M. J. Fath, and J. Beckwith, Genes Dev. 3:1035-1044, 1989. The nusG gene encodes a 181-amino-acid-long polypeptide and is involved in transcription antitermination. The protein product of nusG is essential for bacterial viability. The secE-nusG genes are cotranscribed, with transcripts initiated at the PEG promoter and terminated at the Rho-independent terminator in the region of the rplK promoter. The majority of transcripts are processed at a number of sites in the 5' untranslated leader region by RNase III and are possibly also processed by a second unidentified nuclease. The role of transcript processing in the regulation of secE and nusG has not yet been established. The juxtaposition and coregulation of a protein export factor and a transcriptional factor raise questions concerning a functional connection between the two processes.A cluster of essential genes that encode components of the transcription and translation apparatuses is located at 90 min on the Escherichia coli chromosome. The tuJB operon within the cluster encodes four tRNAs and the translation elongation factor EF-Tu; this operon has been sequenced and its transcription pattern has been partially characterized (1, 28). The rpIKAJL-rpoBC gene cluster encodes, in the following order, the four 50S subunit ribosomal proteins Lll, Li, L10, and L12, and the P and 3' subunits of RNA polymerase; the nucleotide sequence of this region has also been determined, and regulation and transcription of these genes have been studied extensively (5,10,14,21).Two additional genes, secE and nusG, have been located between the tufB and rplKAJL operons (24; Fig. 1 (17) supplemented with glucose (0.2% [wt/ vol]), required amino acids (50 ,ug/ml), thiamine (0.5 ,ug/ml), and NAD when required (1 ,ug/ml). Growth was monitored by measuring the A460. Kanamycin and ampicillin were each added to 50 ,ug/ml when necessary.Plasmid, phage, and bacterial construction. Standard bacteriological techniques, e.g., transformation and P1 transduction, were as previously described (25). The structures and constructions of plasmids are illustrated and described in Fig. 1 (16,22,23). Appropriate DNA fragments were cloned into M13mp18, M13mp19, pUC18, or pUC19 as

SummaryAs an initial step to develop plants as systems to produce enzymes for the treatment of lysosomal storage disorders, Arabidopsis thaliana wild-type (Col-0) plants were transformed with a construct to express human α -L -iduronidase (IDUA; EC 3.2.1.76) in seeds using the promoter and other regulatory sequences of the Phaseolus vulgaris arcelin 5-I gene. IDUA protein was easily detected on Western blots of extracts from the T 2 seeds, and extracts contained IDUA activity as high as 2.9 nmol 4-methylumbelliferone (4 MU)/min/mg total soluble protein (TSP), corresponding to approximately 0.06 µ g IDUA/mg TSP. The purified protein reacted with an antibody specific for xylose-containing plant complex glycans, indicating its transit through the Golgi complex. In an attempt to avoid maturation of the N-linked glycans of IDUA, the same IDUA transgene was introduced into the Arabidopsis cgl background, which is deficient in the activity of N-acetylglucosaminyl transferase I (EC

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Drying of seeds, when imposed prematurely, elicits a switch in metabolism; events unique to development, such as synthesis of storage protein, are terminated, whereas syntheses associated with germination and growth are initiated. To determine the role of desiccation in down-regulating the expression of genes for storage proteins, the desiccation responsiveness of the 5' and 3' regulatory regions of the genes encoding the pea storage protein vicilin and the Brassica napus storage protein napin was tested in transgenic tobacco seed. Chimeric genes were introduced into tobacco; these genes consisted of the coding region of the reporter gene for p-glucuronidase (CUS) and 5' and/or 3' regions from the vicilin or napin genes or, as controls, the same regions derived from constitutively expressed genes, presumed to be desiccation insensitive. In transgenic seed expressing the gene constructs containing the vicilin or napin promoters, CUS activities declined during late seed development, and more dramatically, after imbibition of mature dry seed or prematurely dried seed. In contrast, CUS activities increased after seed rehydration when the constitutive vira1 promoter replaced the storage-protein gene 5' region. Transient expression assays support the hypothesis that premature drying down-regulates the expression of the storage-protein gene promoter. Following desiccation, this region may become insensitive to positive controlling factors; alternatively, changes to trans-acting factors may occur.Seed development and germination are distinct physiological stages of the plant life cycle, in which key metabolic events related to the status of stored reserves contrast markedly. This is reflected in the mRNA subsets prevalent within the seed at these distinct stages. In particular, storage-protein synthesis that is prevalent during mid-to latestage embryogenesis does not occur during germination. Residual mRNAs for storage proteins present in the dry seed are degraded upon subsequent imbibition (Dure, 1985;Bewley and Marcus, 1990;Kermode, 1990). Early metabolic events utilize and depend on components present within the dry seed. After a short lag, new sets of messages are synthesized during germination (SanchezMartinez et al., 1986; Lane, 1991) and also during seedling growth (Harada et al., 1988), when the enzymes necessary '

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