Relative abundance of Δ5-sterols in plasma membrane lipids of root-tip cells correlates with aluminum tolerance of rice |
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Authors: | M. Shahadat Hossain Khan Keitarou Tawaraya Hiroshi Sekimoto Hiroyuki Koyama Yuriko Kobayashi Tetsuya Murayama Masaru Chuba Mihoko Kambayashi Yoshihito Shiono Matsuo Uemura Satoru Ishikawa Tadao Wagatsuma |
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Affiliation: | Faculty of Agriculture, Yamagata University, Tsuruoka 997-8555, Japan; Faculty of Agriculture, Utsunomiya University, Utsunomiya 31-8505, Japan; Faculty of Applied Biological Sciences, Gifu University, Gifu 501-1193, Japan; Shonai Branch, Yamagata General Agricultural Research Center, Tsuruoka 997-7601, Japan; Cryobiosystem Research Center, Faculty of Agriculture, Iwate University, Morioka 020-8550, Japan; National Institute for Agro-Environmental Science, Tsukuba 305-8604, Japan |
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Abstract: | We investigated variations in aluminum (Al) tolerance among rice plants, using ancestor cultivars from the family line of the Al-tolerant and widely cultivated Japonica cultivar, Sasanishiki. The cultivar Rikuu-20 was Al sensitive, whereas a closely related cultivar that is a descendant of Rikuu-20, Rikuu-132, was Al tolerant. These two cultivars were compared to determine mechanisms underlying variations in Al tolerance. The sensitive cultivar Rikuu-20 showed increased permeability of the plasma membrane (PM) and greater Al uptake within 1 h of Al treatment. This could not be explained by organic acid release. Lipid composition of the PM differed between these cultivars, and may account for the difference in Al tolerance. The tolerant cultivar Rikuu-132 had a lower ratio of phospholipids to Δ5-sterols than the sensitive cultivar Rikuu-20, suggesting that the PM of Rikuu-132 is less negatively charged and less permeabilized than that of Rikuu-20. We used inhibitors of Δ5-sterol synthesis to alter the ratio of phospholipids to Δ5-sterols in both cultivars. These inhibitors reduced Al tolerance in Rikuu-132 and its Al-tolerant ancestor cultivars Kamenoo and Kyoku. In addition, Rikuu-132 showed a similar level of Al sensitivity when the ratio of phospholipids to Δ5-sterols was increased to match that of Rikuu-20 after treatment with uniconazole-P, an inhibitor of obtusifoliol-14α-demethylase. These results indicate that PM lipid composition is a factor underlying variations in Al tolerance among rice cultivars. |
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