Trehalose plays an important role in stress tolerance in plants. Trehalose-producing, transgenic rice (Oryza sativa) plants were generated by the introduction of a gene encoding a bifunctional fusion (TPSP) of the trehalose-6-phosphate (T-6-P) synthase (TPS) and T-6-P phosphatase (TPP) of Escherichia coli, under the control of the maize (Zea mays) ubiquitin promoter (Ubi1). The high catalytic efficiency (Seo et al., 2000) of the fusion enzyme and the single-gene engineering strategy make this an attractive candidate for high-level production of trehalose; it has the added advantage of reducing the accumulation of potentially deleterious T-6-P. The trehalose levels in leaf and seed extracts from Ubi1::TPSP plants were increased up to 1.076 mg g fresh weight Ϫ1 . This level was 200-fold higher than that of transgenic tobacco (Nicotiana tabacum) plants transformed independently with either TPS or TPP expression cassettes. The carbohydrate profiles were significantly altered in the seeds, but not in the leaves, of Ubi1::TPSP plants. It has been reported that transgenic plants with E. coli TPS and/or TPP were severely stunted and root morphology was altered. Interestingly, our Ubi1::TPSP plants showed no growth inhibition or visible phenotypic alterations despite the high-level production of trehalose. Moreover, trehalose accumulation in Ubi1::TPSP plants resulted in increased tolerance to drought, salt, and cold, as shown by chlorophyll fluorescence and growth inhibition analyses. Thus, our results suggest that trehalose acts as a global protectant against abiotic stress, and that rice is more tolerant to trehalose synthesis than dicots.is a nonreducing diglucoside that is found in various organisms, including bacteria, algae, fungi, yeast (Saccharomyces cerevisiae), insects, and some plants (Elbein, 1974). Trehalose serves not only as a carbohydrate reserve, but also as a protective agent against a variety of physical and chemical stresses in various organisms (van Laere, 1989;Wiemken, 1990;Eleutherio et al., 1993;Strøm and Kassen, 1993). Trehalose is known to have high water retention activity, which maintains the fluidity of membranes under dry conditions (Leslie et al., 1995). Thus, this sugar allows desert plants to tolerate naturally occurring stresses during cycles of dehydration and rehydration (Drennan et al., 1993;Mü ller et al., 1995).A role for trehalose in stress tolerance has been demonstrated for cryptobiotic plant species, such as the desiccation-tolerant Selaginella lepidophylla. In this case, trehalose accumulation represented 12% of the plant dry weight during dehydration, which probably protected the proteins and membrane structures. Upon rehydration, S. lepidophylla regained complete viability and the trehalose levels declined (Goddijn and van Dun, 1999). Plants accumulate a number of osmoprotective agents, such as Pro, in response to NaCl stress. During osmotic stress in rice (Oryza sativa), trehalose or similar carbohydrates appear to be more important than Pro. It has been shown that treatmen...

Expression patterns of a rice (Oryza sativa) cytochrome c gene OsCc1 and its promoter activity were characterized in transgenic rice plants. OsCc1 transcripts accumulate in most cell types, but to varying levels. Large amounts of OsCc1 transcripts are found in the roots, calli, and suspension cells, but relatively lower in mature leaves, demonstrating its higher levels of expression in non-photosynthetic tissues. Unlike the human cytochrome c gene, which is responsive to cAMP, OsCc1 expression is not enhanced in various rice tissues after dibutyryl cAMP treatments. OsCc1 promoter was linked to the sgfp gene and its activities in different tissues and cell types of transgenic rice plants were analyzed in comparison with the Act1 and RbcS promoters. OsCc1 promoter directs expression in virtually all organs of transgenic plants including roots, leaves, calli, embryos, and suspension cells, showing a particularly high activity in calli and roots. Activity of the OsCc1 promoter was 3-fold higher than Act1 in calli and roots and comparable with RbcS in leaves, representing a useful alternative to the maize (Zea mays) Ubi1 and the rice Act1 promoters for transgene expression in monocots.Several factors increase the expression of chimeric genes in transgenic plants. The choice of promoters affects transgene transcription, resulting in changes not only in concentration, but also in the stage, tissue, and cell specificity of its expression. Over the years, several well-characterized promoters have been made available for transgene expression in plants. However, most of these promoters are from dicot plants. Presently, the cauliflower mosaic virus (CaMV) 35S promoter and its derivatives are among the most commonly used. The CaMV 35S promoter is active in monocots, but its relative strength is substantially lower in monocot than in dicot cells. In addition, it is inactive in some cell types; for example, pollen (Bruce et al., 1989;Christensen et al., 1992; McElroy and Brettell, 1994). Other dicot promoters have also been used for monocot transformation, but activity tends to be lower than for monocot promoters (Wilmink et al., 1995). For example, Kyozuka et al. (1993) reported that expression of the gusA gene driven by a tomato (Lycopersicon esculentum) RbcS promoter is induced by light. However, the expression of the rice (Oryza sativa) RbcS::gusA gene is significantly higher than expression of the tomato RbcS::gusA gene. Conversely, the use of monocot promoters has resulted in a high degree of gene expression in monocots, including rice (McElroy et al., 1991;Cornejo et al., 1993; Kyozuka et al., 1993). Several promoters have been investigated as useful alternatives to drive a high level of expression in monocot transgenesis; for example, the rice Act1 promoter (McElroy et al., 1991), the rice RbcS promoter (Kyozuka et al., 1993; Jang et al., 1999), and the maize (Zea mays) Ubi1 promoter (Uchimiya et al., 1993). In many cases, introns strongly enhance transgene expression in transgenic plants (Wilmink et al., 1995). In ...

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Edited by Ned ManteiCripto-1 and OCT4, expressed in stem cells and cancers, play important roles in tumorigenesis. Here, we demonstrate that Cripto-1 expression is regulated by OCT4 in human embryonic carcinoma NCCIT cells. The endogenous expression of Cripto-1 and OCT4 is significantly reduced during differentiation. Cripto-1 expression is increased by OCT4 overexpression, but decreased by shRNA-mediated OCT4 knockdown. OCT4 overexpression significantly activates Cripto-1 transcriptional activity. A 5 0 -upstream minimal promoter sequence in the gene-encoding Cripto-1 is significantly activated by OCT4 overexpression. Mutation of the putative OCT4-binding site abolishes OCT4-mediated activation of the Cripto-1 promoter. The OCT4 transactivation domains mediate transcriptional activity of the Cripto-1 minimal promoter through direct interaction. Taken together, OCT4 plays an important role as a transcriptional activator of Cripto-1 expression in NCCIT cells.