These experiments were carried out to investigate whether accumulation of carbohydrate leads to decreased expression of genes involved in photosynthesis. Addition of glucose to autotrophic cell suspension cultures of Chenopodium led to a large and reversible decrease of the steady state transcript levels of rbcS, cab and atp8 within 5 h, but did not decrease 18s rRNA or transcript for two glycolytic enzymes. Run-on transcription in isolated nuclei showed that transcription rate had been decreased. f%]Methionine feeding showed that de novo synthesis of Rubisco was inhibited. Decreased rbcS transcript was also found after feeding glucose to detached leaves, and in transgenic plants expressing invertase in the apoplast to inhibit phloem transport, and in leaves on intact tobacco and potato plants which were cold-girdled to decrease export. The decrease of rbcS transcript level occurred within 12 h of coldgirdling. Comparison of carbohydrate content and rbcS transcript level indicated that carbohydrate content perse is not the direct signal for regulation of gene expression. Feeding of transported analogues indicates that metabolism rather than transport of the sugars is required. Over-expression of rbcS was found in low COP, again indicating metabolic control of expression. It is proposed that photosynthetic gene expression is inhibited by metabolic factors related to high carbohydrate content, and that this represents a basic mechanism for the 'sink regulation' of photosynthesis.When 50 mM glucose is added to autotrophically growing Chenopudium rubrum cell suspension cultures, it is rapidly 81 7

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A new strategy to achieve easily scalable triple stimuli-responsive elastomeric opal films for applications as stretch-tunable photonic band gap materials is reported. Novel monodisperse highly functional core-interlayer-shell beads are obtained by semicontinuous emulsion polymerization featuring a temperature-sensitive fluorescent rhodamine dye either locally restricted in the core or the shell of prepared beads. After extrusion and compression molding, homogeneous elastomeric opal films with fascinating stretch-tunable and temperature-dependent fluorescent properties can be obtained. Applying strains of only a few percent lead to significant blue shift of the reflected colors making these films excellent candidates for applications as deformation sensors. Higher strains up to 90% lead to a tremendous Bragg reflection color change caused by transition from the (111) to the (200) lattice plane. The well-ordered opaline structure with its stop band at the emission frequency of the incorporated fluorescent dye shows remarkable angle-dependent fluorescence suppression. Herein described elastomeric opal films can be valuable in a wide range of applications such as rewritable 3D optical data storage, tunable laser action, and sensing materials.

The ndh genes encoding for the subunits of NAD(P)H dehydrogenase complex represent the largest family of plastid genes without a clearly defined function. Tobacco (Nicotiana tabacum) plastid transformants were produced in which the ndhB gene was inactivated by replacing it with a mutant version possessing translational stops in the coding region. Western-blot analysis indicated that no functional NAD(P)H dehydrogenase complex can be assembled in the plastid transformants. Chlorophyll fluorescence measurements showed that dark reduction of the plastoquinone pool by stromal reductants was impaired in ndhB-inactivated plants. Both the phenotype and photosynthetic performance of the plastid transformants was completely normal under favorable conditions. However, an enhanced growth retardation of ndhB-inactivated plants was revealed under humidity stress conditions causing a moderate decline in photosynthesis via stomatal closure. This distinctive phenotype was mimicked under normal humidity by spraying plants with abscisic acid. Measurements of CO 2 fixation demonstrated an enhanced decline in photosynthesis in the mutant plants under humidity stress, which could be restored to wild-type levels by elevating the external CO 2 concentration. These results suggest that the plastid NAD(P)H:plastoquinone oxidoreductase in tobacco performs a significant physiological role by facilitating photosynthesis at moderate CO 2 limitation.

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