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Visualization of Uptake of Mineral Elements and the Dynamics of Photosynthates in Arabidopsis by a Newly Developed Real-Time Radioisotope Imaging System (RRIS).

Sugita R, Kobayashi NI, Hirose A, Saito T, Iwata R, Tanoi K, Nakanishi TM - Plant Cell Physiol. (2016)

Bottom Line: In contrast, high accumulation of(28)Mg,(45)Ca and(54)Mn was found in the basal part of the main stem.Based on this time-course analysis, the velocity of ion movement in the main stem was calculated, and found to be fastest for S and K among the ions we tested in this study.These results show that this real-time radioisotope imaging system allows visualization of many nuclides over a long time-course and thus constitutes a powerful tool for the analysis of various physiological phenomena.

View Article: PubMed Central - PubMed

Affiliation: Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1, Yayoi, Bunkyo-ku, Tokyo, 113-8657 Japan.

No MeSH data available.


Related in: MedlinePlus

Heat-girdling treatment to discriminate the xylem flow from the phloem flow. (a) 14C distribution images acquired by the imaging plate after heat-girdling treatment applied to the Arabidopsis main stem (red arrows) confirmed that the heat-girdling treatment successfully inhibited the phloem flow directed to the apical part of the main stem. 14CO2 was supplied to rosette leaves. (1) Sample picture, (2) 14C distribution images acquired by an imaging plate, (3) brightness of the center images was enhanced so that the 14C signal in the inflorescence was visible. (b) Macro-RRIS images of 28Mg and 32P in Arabidopsis with the heat-girdling treatment at the position marked with the red arrows. The exposure time of the camera was set to 15 min. ROIs were indicated with the blue circle (ROI: A) and red circle (ROI:B) in the image. (c) The distribution profile of 28Mg (1) and 32P (2) along the main stem after 16 h absorption of radiotracers acquired by the macro-RRIS experiments shown in (b). The position of the heat-girdling treatment was marked with the red arrow. x-axis, the distance (mm) from the bottom part of the inflorescence. (d) Time course of 28Mg (1, 2) and 32P (3, 4) signal intensity in ROI:A (blue circle) and ROI:B (red circle) as illustrated in Fig. 2d. The linear components in (1) and (3) were extracted in (2) and (4), respectively.
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pcw056-F3: Heat-girdling treatment to discriminate the xylem flow from the phloem flow. (a) 14C distribution images acquired by the imaging plate after heat-girdling treatment applied to the Arabidopsis main stem (red arrows) confirmed that the heat-girdling treatment successfully inhibited the phloem flow directed to the apical part of the main stem. 14CO2 was supplied to rosette leaves. (1) Sample picture, (2) 14C distribution images acquired by an imaging plate, (3) brightness of the center images was enhanced so that the 14C signal in the inflorescence was visible. (b) Macro-RRIS images of 28Mg and 32P in Arabidopsis with the heat-girdling treatment at the position marked with the red arrows. The exposure time of the camera was set to 15 min. ROIs were indicated with the blue circle (ROI: A) and red circle (ROI:B) in the image. (c) The distribution profile of 28Mg (1) and 32P (2) along the main stem after 16 h absorption of radiotracers acquired by the macro-RRIS experiments shown in (b). The position of the heat-girdling treatment was marked with the red arrow. x-axis, the distance (mm) from the bottom part of the inflorescence. (d) Time course of 28Mg (1, 2) and 32P (3, 4) signal intensity in ROI:A (blue circle) and ROI:B (red circle) as illustrated in Fig. 2d. The linear components in (1) and (3) were extracted in (2) and (4), respectively.

Mentions: In the inflorescence, both xylem and phloem flow can affect ion transport. To determine ion movement via the xylem, we assessed the transport and distribution of 28Mg and 32P in which phloem flow in the main stem was inhibited by heat-girdling (Fig. 3). The inhibitory effect of heat-girdling on phloem flow in the main stem was assessed by the distribution of 14C-labeled photosynthates (Fig. 3a). After 14CO2 was supplied to rosette leaves, the accumulation of 14C signal in the apical stem was shown to be abolished by heat-girdling (Fig. 3a), thus indicating the reliability of our heat-girdling technique. Further, 28Mg displayed a distribution pattern along the main stem that was similar to that of non-treated plants (Figs. 2c: 6, 3b: 1, 3c: 1). A kinetic analysis showed that the velocity of Mg2+ in the xylem flow was 5.5 mm h−1 (Fig. 3d: 2), a value in the range of that found in intact Arabidopisis (Fig. 2d: 3, 4). Thus, the upward Mg2+ movement within the third internode of the main stem is likely to be mediated mainly by xylem flow, while the phloem contribution is scarce during the first 24 h of root absorption. In contrast, heat-girdling resulted in strong 32P signal accumulation at the bottom of the main stem (Fig. 3b: 2, 3c: 2), which was never observed in untreated Arabidopsis (Fig. 2c: 2). The difference in the time taken for the 32P signal intensity per square millimeter to reach LOQ in ROI:A and in ROI:B was 1 h; thus, the velocity of P in the xylem stream was calculated to be 30 mm h−1(Fig. 3d: 4), and thus slower than in intact plants (Fig. 2d: 7, 8). In addition, unlike in untreated Arabidopsis (Fig. 2d: 5, 6), the rate of increase of 32P signal intensity in ROI:A as well as in ROI:B in plants with girdled inflorescences gradually decreased (Fig. 3d: 3). As a result, the 32P radioactivity in ROI:A, which began to increase earlier than in ROI:B, reached the same level as for ROI:B after 18 h. These results suggest that the large signal increase in ROI:A observed after 5 h of imaging of intact plants (Fig. 2d: 5, 6) was due to phloem transport. In this context, the contribution of phloem flow to phosphate transport toward the shoot meristem could be significant even within 24 h of root absorption. Furthermore, based on our observation that the gap between 32P radioactivity in ROI:A and that in ROI:B increased with time, phosphate transport via the phloem along the main stem was inferred to be slower than via the xylem.Fig. 3


Visualization of Uptake of Mineral Elements and the Dynamics of Photosynthates in Arabidopsis by a Newly Developed Real-Time Radioisotope Imaging System (RRIS).

Sugita R, Kobayashi NI, Hirose A, Saito T, Iwata R, Tanoi K, Nakanishi TM - Plant Cell Physiol. (2016)

Heat-girdling treatment to discriminate the xylem flow from the phloem flow. (a) 14C distribution images acquired by the imaging plate after heat-girdling treatment applied to the Arabidopsis main stem (red arrows) confirmed that the heat-girdling treatment successfully inhibited the phloem flow directed to the apical part of the main stem. 14CO2 was supplied to rosette leaves. (1) Sample picture, (2) 14C distribution images acquired by an imaging plate, (3) brightness of the center images was enhanced so that the 14C signal in the inflorescence was visible. (b) Macro-RRIS images of 28Mg and 32P in Arabidopsis with the heat-girdling treatment at the position marked with the red arrows. The exposure time of the camera was set to 15 min. ROIs were indicated with the blue circle (ROI: A) and red circle (ROI:B) in the image. (c) The distribution profile of 28Mg (1) and 32P (2) along the main stem after 16 h absorption of radiotracers acquired by the macro-RRIS experiments shown in (b). The position of the heat-girdling treatment was marked with the red arrow. x-axis, the distance (mm) from the bottom part of the inflorescence. (d) Time course of 28Mg (1, 2) and 32P (3, 4) signal intensity in ROI:A (blue circle) and ROI:B (red circle) as illustrated in Fig. 2d. The linear components in (1) and (3) were extracted in (2) and (4), respectively.
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pcw056-F3: Heat-girdling treatment to discriminate the xylem flow from the phloem flow. (a) 14C distribution images acquired by the imaging plate after heat-girdling treatment applied to the Arabidopsis main stem (red arrows) confirmed that the heat-girdling treatment successfully inhibited the phloem flow directed to the apical part of the main stem. 14CO2 was supplied to rosette leaves. (1) Sample picture, (2) 14C distribution images acquired by an imaging plate, (3) brightness of the center images was enhanced so that the 14C signal in the inflorescence was visible. (b) Macro-RRIS images of 28Mg and 32P in Arabidopsis with the heat-girdling treatment at the position marked with the red arrows. The exposure time of the camera was set to 15 min. ROIs were indicated with the blue circle (ROI: A) and red circle (ROI:B) in the image. (c) The distribution profile of 28Mg (1) and 32P (2) along the main stem after 16 h absorption of radiotracers acquired by the macro-RRIS experiments shown in (b). The position of the heat-girdling treatment was marked with the red arrow. x-axis, the distance (mm) from the bottom part of the inflorescence. (d) Time course of 28Mg (1, 2) and 32P (3, 4) signal intensity in ROI:A (blue circle) and ROI:B (red circle) as illustrated in Fig. 2d. The linear components in (1) and (3) were extracted in (2) and (4), respectively.
Mentions: In the inflorescence, both xylem and phloem flow can affect ion transport. To determine ion movement via the xylem, we assessed the transport and distribution of 28Mg and 32P in which phloem flow in the main stem was inhibited by heat-girdling (Fig. 3). The inhibitory effect of heat-girdling on phloem flow in the main stem was assessed by the distribution of 14C-labeled photosynthates (Fig. 3a). After 14CO2 was supplied to rosette leaves, the accumulation of 14C signal in the apical stem was shown to be abolished by heat-girdling (Fig. 3a), thus indicating the reliability of our heat-girdling technique. Further, 28Mg displayed a distribution pattern along the main stem that was similar to that of non-treated plants (Figs. 2c: 6, 3b: 1, 3c: 1). A kinetic analysis showed that the velocity of Mg2+ in the xylem flow was 5.5 mm h−1 (Fig. 3d: 2), a value in the range of that found in intact Arabidopisis (Fig. 2d: 3, 4). Thus, the upward Mg2+ movement within the third internode of the main stem is likely to be mediated mainly by xylem flow, while the phloem contribution is scarce during the first 24 h of root absorption. In contrast, heat-girdling resulted in strong 32P signal accumulation at the bottom of the main stem (Fig. 3b: 2, 3c: 2), which was never observed in untreated Arabidopsis (Fig. 2c: 2). The difference in the time taken for the 32P signal intensity per square millimeter to reach LOQ in ROI:A and in ROI:B was 1 h; thus, the velocity of P in the xylem stream was calculated to be 30 mm h−1(Fig. 3d: 4), and thus slower than in intact plants (Fig. 2d: 7, 8). In addition, unlike in untreated Arabidopsis (Fig. 2d: 5, 6), the rate of increase of 32P signal intensity in ROI:A as well as in ROI:B in plants with girdled inflorescences gradually decreased (Fig. 3d: 3). As a result, the 32P radioactivity in ROI:A, which began to increase earlier than in ROI:B, reached the same level as for ROI:B after 18 h. These results suggest that the large signal increase in ROI:A observed after 5 h of imaging of intact plants (Fig. 2d: 5, 6) was due to phloem transport. In this context, the contribution of phloem flow to phosphate transport toward the shoot meristem could be significant even within 24 h of root absorption. Furthermore, based on our observation that the gap between 32P radioactivity in ROI:A and that in ROI:B increased with time, phosphate transport via the phloem along the main stem was inferred to be slower than via the xylem.Fig. 3

Bottom Line: In contrast, high accumulation of(28)Mg,(45)Ca and(54)Mn was found in the basal part of the main stem.Based on this time-course analysis, the velocity of ion movement in the main stem was calculated, and found to be fastest for S and K among the ions we tested in this study.These results show that this real-time radioisotope imaging system allows visualization of many nuclides over a long time-course and thus constitutes a powerful tool for the analysis of various physiological phenomena.

View Article: PubMed Central - PubMed

Affiliation: Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1, Yayoi, Bunkyo-ku, Tokyo, 113-8657 Japan.

No MeSH data available.


Related in: MedlinePlus