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981.
Tomomichi Chonan Hiroaki Tanaka Daisuke Yamamoto Miyoko Yashiro Takahiro Oi Daisuke Wakasugi Ayumi Ohoka-Sugita Fusayo Io Hiroko Koretsune Akira Hiratate 《Bioorganic & medicinal chemistry letters》2010,20(13):3965-3968
Acetyl-CoA carboxylases (ACCs), the rate limiting enzymes in de novo lipid synthesis, play important roles in modulating energy metabolism. The inhibition of ACC has demonstrated promising therapeutic potential for treating obesity and type 2 diabetes mellitus in transgenic mice and preclinical animal models. We describe herein the structure-based design and synthesis of a novel series of disubstituted (4-piperidinyl)-piperazine derivatives as ACC inhibitors. Our structure-based approach led to the discovery of the indole derivatives 13i and 13j, which exhibited potent in vitro ACC inhibitory activity. 相似文献
982.
983.
In rice, light is known to inhibit the growth of coleoptiles and seminal roots of seedlings through phytochrome. Here we investigated the light-induced growth inhibition of seminal roots and compared the results with those recently determined for coleoptiles. Although three rice phytochromes, phyA, phyB and phyC functioned in a similar manner in coleoptile and seminal root, the Bunsen-Roscoe law of reciprocity was not observed in the growth inhibition of seminal root. We also found coiling of the seminal root at the root tip which appeared to be associated with the photoinhibition of seminal root growth. This could be a new light-induced phenomenon in certain cultivars of rice.Key words: growth, hypocotyl, Oryza sativa, phytochrome, seminal rootPhytochrome-mediated growth inhibition was reported for both coleoptiles and seminal roots of rice seedlings in the same year by two research groups in Nagoya and Tohoku University in Japan, respectively.1,2 Forty years after the findings, a detailed photobiological study was carried out for the coleoptile growth inhibition.3 In this study, we examined photoinhibition of seminal root growth, and found similarities and differences between light-induced growth inhibition of the two organs in rice seedlings. Although coleoptile growth was inhibited by pulses of light, growth inhibition of seminal roots required light irradiation longer than 6 h. The Bunsen-Roscoe law of reciprocity was not observed in the growth inhibition of seminal root. Action spectra were determined for the growth inhibition of coleoptiles, and the mode of inhibition was found to depend on the age of the coleoptiles. At the early stage of development [40 h after inducing germination (AIG)], photoinhibition was predominantly due to the phyB-mediated low-fluence response (LFR), but at the late developmental stage (80 h AIG), it consisted of the phyA-mediated very low-fluence response (VLFR) as well as the phyB-mediated LFR.3,4 In the case of root growth, the sensitivity of photoinhibition also depended on age, and was most sensitive in the period of 48–96 h AIG when seedlings were irradiated for 24 h. Using rice phytochrome mutants,5 we found that far-red light for root growth inhibition was perceived exclusively by phyA, that red light was perceived by both phyA and phyB, and that phyC had little or no role in growth inhibition. Furthermore, the fluence rate required for phyB-mediated inhibition was more than 10,000-fold greater than that required for phyA-mediated inhibition. These characteristics of photoinhibition in seminal roots are similar to those found in coleoptiles at the late stage of development.3 In seminal roots, photoinhibition appeared to be mediated by photoreceptors in the root itself.Interestingly, coiling of the root tips always occurred when root growth was inhibited under the light condition (Fig. 1B). Under continuous light irradiation, rice seeds germinated ∼30 h AIG. Seminal roots formed a coil at the root tips during the 48–96 h period AIG, and stopped growing. When they were irradiated for only 24 h on the 3rd day AIG, coils started to form just after the end of irradiation. The roots continued to coil for ∼28 h and then began growing straight again (Fig. 1C). The coils were larger and looser than those formed under continuous light condition (Fig. 1, Open in a separate windowFigure 1Light irradiation induces coiling of root tips in rice seedlings (Oryza sativa cv. Nipponbare). A rice seedling was grown in the dark (A), or in continuous white light (55 µole m−2 s−1) (B) for 7 d at 28°C. In (C), it was irradiated by white light for 24 h during the 48–72 h period after inducing germination, and kept in the dark again until the 7th day. Arrows and arrowheads indicate the seminal and crown roots, respectively. Seedlings were grown in glass tubes of 3-cm diameter.
Open in a separate window* Mean and SD of 4-7 seedlings.We also found that light exposure had an opposite effect on the growth of the seminal and crown roots of rice seedlings. Light inhibited the growth of seminal roots, whereas it promoted the growth of crown roots. In fact, light was found to promote growth of Arabidopsis primary roots, in which phyA and phyB were found to be responsible for photoperception as well as photosynthetic activity.6 In rice seedlings, growth orientation of the crown roots is also affected by light exposure, whereas growth orientation of the seminal roots is controlled solely by the gravity vector. The crown roots grow in a horizontal direction in the dark, while they grow toward the gravity vector in the light.7 The contrasting responses to light in the seminal and crown roots are likely to help the transition of rice seedlings from the embryonic root system, in which the seminal roots are predominant, to the fibrous root system, which contains numerous crown roots. 相似文献
Table 1
The size of coil of root tips formed after white light irradiationLight irradiation | Diameter* (mm) | Length* (mm) | Number of turns* |
Continuous irradiation for 7 d | 1.96 ± 0.41 | 2.70 ± 0.63 | 4.6 ± 0.8 |
24 h-long irradiation during the 48–72 h period after inducing germination | 2.60 ± 0.44 | 3.33 ± 0.19 | 2.3 ± 0.5 |
984.
The photoreceptors for chloroplast photorelocation movement have been known, but the signal(s) raised by photoreceptors remains unknown. To know the properties of the signal(s) for chloroplast accumulation movement, we examined the speed of signal transferred from light-irradiated area to chloroplasts in gametophytes of Adiantum capillus-veneris. When dark-adapted gametophyte cells were irradiated with a microbeam of various light intensities of red or blue light for 1 min or continuously, the chloroplasts started to move towards the irradiated area. The speed of signal transfer was calculated from the relationship between the timing of start moving and the distance of chloroplasts from the microbeam and was found to be constant at any light conditions. In prothallial cells, the speed was about 1.0 µm min−1 and in protonemal cells about 0.7 µm min−1 towards base and about 2.3 µm min−1 towards the apex. We confirmed the speed of signal transfer in Arabidopsis thaliana mesophyll cells under continuous irradiation of blue light, as was about 0.8 µm min−1. Possible candidates of the signal are discussed depending on the speed of signal transfer.Key words: Adiantum capillus-veneris, Arabidopsis thaliana, blue light, chloroplast movement, microbeam, red light, signalOrganelle movement is essential for plant growth and development and tightly regulated by environmental conditions.1 It is well known that light regulates chloroplast movement in various plant species. Chloroplast movement can be separated into three categories, (1) photoperception by photoreceptors, (2) signal transduction from photoreceptor to chloroplasts and (3) movement of chloroplasts and has been analyzed from a physiological point of view.2 We recently identified the photoreceptors in Arabidopsis thaliana, fern Adiantum capillus-veneris, and moss Physcomitrella patens. In A. thaliana, phototropin 2 (phot2) mediates the avoidance movement,3,4 whereas both phototropin 1 (phot1) and phot2 mediate the accumulation response.5 A chimeric photoreceptor neochrome 1 (neo1)6 was identified as a red/far-red and blue light receptor that mediates red as well as blue light-induced chloroplast movement in A. capillusveneris.7 Interestingly, neo1 mediated red and blue light-induced nuclear movement and negative phototropic response of A. capillus-veneris rhizoid cells.8,9 On the mechanism of chloroplast movement, we also found a novel structure of actin filaments that appeared between chloroplast and the plasma membrane at the front side of moving chloroplast.10 Recent studies using the technique of microbeam irradiation have revealed that chloroplasts do not have a polarity for light-induced accumulation movement and can move freely in any direction both in A. capillus-veneris prothallial cells and in A. thaliana mesophyll cells.11 However, the signal that may be released from photoreceptors and transferred to chloroplasts remains unknown.To understand the properties of the signal for the chloroplast accumulation response, we examined the speed of signal transfer in dark-adapted A. capillus-veneris gametophyte cells and A. thaliana mesophyll cells by partial cell irradiation with a red and/or blue microbeam of various light intensities for 1 min and the following continuous irradiation, respectively.12As shown in Figure 1, the relation between the distance of chloroplasts from the microbeam and the timing when each chloroplast started moving toward the microbeam irradiated area (shown as black dots in Fig. 1) was obtained and plotted. The lag time between the onset of microbeam irradiation and the timing of start moving of chloroplasts is the time period needed for a signal to reach each chloroplast. To obtain more accurate data many chloroplasts at various positions were used. The slope of the approximate line indicates the average speed of the signal transfer. Shown with a protonemal cell at the left side of this figure is an instance where the speed of signal transfer from basal-to-apical (acropetal) direction is obtained.Open in a separate windowFigure 1How to calculate the speed of signal transfer in the basal cell of two-celled protonema of Adiantum capillus-veneris. The relationship between the distance of chloroplast position from the edge of the microbeam to the center of each chloroplast as shown in left side of figure and the timing of chloroplast movement initiated shown as the black dots was obtained. Inclination of the approximate lines connecting dots indicates the speeds of the signal transfer.In protonemal cells, which are tip-growing linear cells, the average speed of signal transfer was about 2.3 µm min−1 from basal-to-apical (acropetal) and about 0.7 µm min−1 from apical-to-basal (basipetal) directions. These values were almost constant irrespective of light intensity, wavelength, irradiation period, and the region of the cell irradiated.12 The difference of speed between basipetal and acropetal directions may be depending on cell polarity. The signal transfer in prothallial cells of A. capillus-veneris and mesophyll cells of A. thaliana was about 1.0 µm min−1 to any direction, probably because they may not have a polarity comparing to protonemal cells or have a weak polarity if any. Thus, the speed of signal transfer must be conserved in most land plants,12 if not influenced by strong polarity. R1W m−2 R1W m−2 B1W m−2 R0.1W m−2 R10W m−2 B10W m−2 1 min countinuous countinuous countinuous countinuous countinuous Protonemal cell (towards apical region) 2.32 2.37 2.28 2.41 2.39 Protonemal cell (towards basal region) 0.58 0.73 0.80 0.74 0.86 Prothallial cell 1.13 0.92 1.10 1.08 0.95 Arabidopsis thaliana 0.70