Abstract Background In Arabidopsis , ETO1 (ETHYLENE-OVERPRODUCER1) is a negative regulator of ethylene evolution by interacting with AtACS5, an isoform of the rate-limiting enzyme, 1-aminocyclopropane-1-carboxylate synthases (ACC synthase or ACS), in ethylene biosynthetic pathway. ETO1 directly inhibits the enzymatic activity of AtACS5. In addition, a specific interaction between ETO1 and AtCUL3, a constituent of a new type of E3 ubiquitin ligase complex, suggests the molecular mechanism in promoting AtACS5 degradation by the proteasome-dependent pathway. Because orthologous sequences to ETO1 are found in many plant species including tomato, we transformed tomato with Arabidopsis ETO1 to evaluate its ability to suppress ethylene production in tomato fruits. Results Transgenic tomato lines that overexpress Arabidopsis ETO1 ( ETO1 -OE) did not show a significant delay of fruit ripening. So, we performed yeast two-hybrid assays to investigate potential heterologous interaction between ETO1 and three isozymes of ACC synthases from tomato. In the yeast two-hybrid system, ETO1 interacts with LE-ACS3 as well as AtACS5 but not with LE-ACS2 or LE-ACS4, two major isozymes whose gene expression is induced markedly in ripening fruits. According to the classification of ACC synthases, which is based on the C-terminal amino acid sequences, both LE-ACS3 and AtACS5 are categorized as type 2 isozymes and possess a consensus C-terminal sequence. In contrast, LE-ACS2 and LE-ACS4 are type 1 and type 3 isozymes, respectively, both of which do not possess this specific C-terminal sequence. Yeast two-hybrid analysis using chimeric constructs between LE-ACS2 and LE-ACS3 revealed that the type-2-ACS-specific C-terminal tail is required for interaction with ETO1. When treated with auxin to induce LE-ACS3 , seedlings of ETO1 -OE produced less ethylene than the wild type, despite comparable expression of the LE-ACS3 gene in the wild type. Conclusion These results suggest that ETO1 family proteins specifically interact with and negatively regulate type 2 ACC synthases. Our data also show that Arabidopsis ETO1 can regulate type 2 ACS in a heterologous plant, tomato.
Antioxidative constituents in roasted sesame seed oil were studied mainly by an antioxidative assay and HPLC analysis, in comparison with unroasted sesame seed oil. The main active constituent in fresh roasted seed oil was γ-tocopherol, but after heating at frying temperature for 1-2 hr, this was identified as sesamol, which was produced by hydrolysis of sesamolin that is present to a large degree in roasted sesame seed oil. This conversion of sesamolin to sesamol is catalyzed by acids.
A new integrated-injection-logic circuit which consists of multiple (m) layers of I2L circuit blocks and operates with an extremely low power dissipation is discussed. The same logic function is realised with m-times less power than a conventional I2L circuit.
The destructive secondary-breakdown mechanism of high-voltage n-channel power MOSFET's is discussed. A model is proposed in which the secondary breakdown is caused primarily by the negative-resistance effects of a parasitic bipolar transistor structure. The model suggests that destructive breakdown can be suppressed by a new no-surface-breakdown structure fabricated on a p - on p + epitaxial wafer. Power MOSFET's having this structure have been realized and are completely free from secondary breakdowns, as suggested by the model. In addition, experimental evidence for excellent thermal stability of the power MOSFET is given by infrared scanner measurements of the temperature rise in the chip compared with bipolar transistors. An n-channel planar power MOSFET with a 400-W power limitation at 220-V breakdown voltage and a maximum current of 12 A has been successfully fabricated.
Control of growth, fruit yield and sugar content of fruits were studied by comparing between tomato plants grafted on rootstocks of tomato (Lycopersicon esculentum Mill.) and scarlet eggplant (Solanum integrifolium Poir.). Vegetative growth tended to be depressed and the incidence of blossom end rot of fruits to be increased by grafting on scarlet egg-plant rootstocks. Fruit yield on scarlet eggplant rootstocks was lower than that on tomato rootstocks. Guttation was not observed in plants grafted on scarlet eggplant rootstocks. However, concentrations of leaf chlorophyll and the soluble solids and sugar contents in fruits were all higher in plants grafted on scarlet eggplant than on tomato rootstocks. These results indicate that plants grafted on scarlet eggplant rootstocks are likely in a state of water deficiency.
