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>2004[@BACKi2003j | 2004 | NEXTi2005j@]

Ito, K., Ito, T., Onda, Y., and Uemura, M. (2004)
Temperature-triggered periodical thermogenic oscillations in skunk cabbage (Symplocarpus foetidus).
Plant Cell Physiol. 45: 257-264.

The natural occurrence of temperature-triggered and light-independent thermogenic oscillation in the spadix of skunk cabbage, Symplocarpus foetidus, was discovered. The identified thermogenic oscillator had an accurate periodical cycle (ca. 60 min per cycle) that apparently responded to an increase or decrease in the spadix temperature with a threshold of less than 0.9 . Neither a constant ambient air temperature nor transient changes in the ambient air temperature within 10 min ( 19 15 19 ) induced the temperature oscillation in the spadix. Moreover, the periodical cycles were independent of the weight of the spadix (2.5-9.2 g) and the amplitudes of the temperature oscillations were correlated with the magnitude of the changes in the spadix temperatures. These results imply that periodical temperature oscillations in the spadix of S. foetidus possess a quantitative regulatory process that involves a temperature sensation and subsequent heat production. Based on these results, we propose a time-dependent thermogenic oscillatory model that acts as a precise thermal regulator under dynamic environmental temperature changes.

Tanaka, D., Niino, T., Isuzugawa, K., Hikage, T. and Uemura, M. (2004)
Cryopreservation of shoot apices of in-vitro grown Gentian plants: comparison of vitrification and encapsulation-vitrification protocols.
CryoLetters 25: 167-176.

Using vitrification and encapsulation-vitrification protocols, we successfully cryopreserved shoot apices from in-vitro plants of different Gentiana cultivars/lines. Although both protocols gave high survival percentages after storage in liquid nitrogen, the encapsulation-vitrification protocol had several distinct advantages over the vitrification protocol: (i) survival was higher under optimal conditions, (ii) the range of optimal exposure periods to the plant vitrification solution 2 (PVS2) was broader, and (iii) regrowth of cryopreserved shoot apices was apparently more vigorous and faster. Shoot apices from ten cultivars/lines of three Gentiana species (G. scabra, G. triflora, and G. pneumonanthe ) were successfully cryopreserved using the two protocols with average survival of 49.0% and 73.7% for vitrification and encapsulation-vitrification, respectively. These results indicate that the two protocols optimized in the present study are promising for cryopreservation of a wide range of Gentiana genetic resources.

Kamata, T. and Uemura, M. (2004)
Solute accumulation in wheat seedlings during cold acclimation: contribution to increased freezing tolerance.
CryoLetters 25: 311-322.

Accumulation of sugars, amino acids and glycinebetaine in leaf tissues during cold acculimation was simultaneously monitored and compared in three wheat cultivars that have different freezing tolelance. Freezing tolerance was the order of cv. Norstar (NO) > cv. Chihokukomugi (CH) cv. Haruyutaka (HA). During cold acclimation, there was a significant increase in osmotic concentration in the three cultivars. The increase was largely due to the increase in sugars and the extent of the increase was the greatest in NO and the leastin HA. White there was a considerable increase in glucose, fluctose and sucrose during the first week of cold acclimation, the increase in raffinose occurred only after the second week. The total sugar content was the order of NO > CH > HA after 4 weeks of cold acclimation. Proline increased in all cultivars after 1 week pf cold acclimation but a prolonged cold acclimation resulted in different profiles: no further increase occurred in HA while an additional increase occurred in other two cultivars. In all three cultivars, a noticeable increase of glycinebetaine occurred only after the second week of cold acclimation with the amount being the order of NO > CH > HA. It is concluded that a substantial part of the increase in osmotic contribution of each compatible solute is cultivar-specific and can be associated with the degree of the maximum freezing tolerance attainable.

Tanaka, N., Fujita, M., Handa, H., Murayama, S., Uemura, M., Kawamura, Y., Mitsui, T., Mikami, S., Tozawa, Y., Yoshinaga, T. and Komatsu, S. (2004)
Proteomics of the rice cell: systematic identification of the protein populations in subcellular compartments.
Molecular, Genetics and Genomics 271: 566-576.

Despite recent progress in sequencing the complete genome of rice (Oryza sativa), the proteome of this species remains poorly understood. To extend our knowledge of the rice proteome, the subcellular compartments, which include plasma membrabes (PM), vacuolar membranes (VM), Golgi membranes (GM), mitochondria (MT), and chloroplasts (CP), ware purified from rice seedlings and cultured suspention cells. The proteins of each of these compartments were then systematically analyzed using two-dimensional (2D) electrophoresis, mass spectrometry, and Edman sequencing, followed by database searching. In all, 58 of the 464 spots detected by 2D electrophoresis in PM, 43 of the 141 spots in VM, 46 of the 361 spots in GM, 146 in the 672 spots in MT, and 89 of the 252 spots in CP could be identified by this procedure. The characterized proteins were found to be involved in various processes, such as respiration and the citric acid cycle in MT; photosynthesis and ATP synthesis in CP; and antifungal defense and signal systems in the membranes. Edman degradation revealed that 60-98% of N-terminal sequences were blocked, and antifungal defense and signal systems in the membranes. Edman degradation revealed that 60-98% of N-terminal sequences were blocked, and the ratios of blocked to unblocked proteins in the proteomes of the various subcellular compartments differed. The data on the proteomes of subcellular compartments in rice will be valuable for resolving questions in functional genomics as well as for genome-wide exploration of plant function.

Sarker, B. C., Hara, M. and Uemura, M. (2004)
Comparison of response of two C3 species to leaf water relation, praline synthesis, gas exchange and water use under periodic water stress.
Journal of Plant Biology 47: 33-41.

Water relations, praline content and gas exchange of leaf were investigated under periodic water stress for two C3 plants (eggplant and tomato) in a greenhouse to study comparative adaptive responses. Although both species showed reduced water content of leaf and increased osmolality and praline content under low soil water potential, the recovery capacity after the stress was better in eggplant than tomato. Both spiecies over-accumulated praline under low soil water potential during drought. Proline was directly corresponding with osmolality during stress, and dehydration stress reduced the gas exchange parameters such as transpiration rate (RT), stomatal conductance (GS), and photosynthesis rate (Pn). At the final stage of the experiment both species showed 2.6 and 3.3 times lower Pn and 27 and 19 times lower GS for eggplant and tomato, respectively, as compared to control. But after stress was relieved by rewatering, both plants increased GS for 2 to 3 times and Pn for 4.5 times. Eggplant showed better water use efficiency (WUE) in indicated more efficient recovery than that of tomato. Higher biomass allocation at root and fruit parts in eggplant indicated more efficient recovery than that of tomato. These findings inferred that both C3 plants developed internal complementary drought survival mechanism by lowering water content, increasing praline, and decreasing stomatal conductance but eggplants water stress condition.

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