Cold stability of microtubules in wood-forming tissues of conifers during seasons of active and dormant cambium |
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Authors: | Shahanara Begum Masaki Shibagaki Osamu Furusawa Satoshi Nakaba Yusuke Yamagishi Joto Yoshimoto Hyun-O Jin Yuzou Sano Ryo Funada |
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Institution: | (1) Faculty of Agriculture, Tokyo University of Agriculture and Technology, Fuchu-Tokyo 183-8509, Japan;(2) Faculty of Agriculture, Bangladesh Agricultural University, Mymensingh, 2202, Bangladesh;(3) Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan;(4) College of Life Sciences, Kyung Hee University, Yongin, 446-701, Korea; |
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Abstract: | The cold stability of microtubules during seasons of active and dormant cambium was analyzed in the conifers Abies firma, Abies sachalinensis and Larix leptolepis by immunofluorescence microscopy. Samples were fixed at room temperature and at a low temperature of 2–3°C to examine the
effects of low temperature on the stability of microtubules. Microtubules were visible in cambium, xylem cells and phloem
cells after fixation at room temperature during seasons of active and dormant cambium. By contrast, fixation at low temperature
depolymerized microtubules in cambial cells, differentiating tracheids, differentiating xylem ray parenchyma and phloem ray
parenchyma cells during the active season. However, similar fixation did not depolymerize microtubules during cambial dormancy
in winter. Our results indicate that the stability of microtubules in cambial cells and cambial derivatives at low temperature
differs between seasons of active and dormant cambium. Moreover, the change in the stability of microtubules that we observed
at low temperature might be closely related to seasonal changes in the cold tolerance of conifers. In addition, low-temperature
fixation depolymerized microtubules in cambial cells and differentiating cells that had thin primary cell walls, while such
low-temperature fixation did not depolymerize microtubules in differentiating secondary xylem ray parenchyma cells and tracheids
that had thick secondary cell walls. The stability of microtubules at low temperature appears to depend on the structure of
the cell wall, namely, primary or secondary. Therefore, we propose that the secondary cell wall might be responsible for the
cold stability of microtubules in differentiating secondary xylem cells of conifers. |
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