Journal Article

Dark conditions enhance aluminum tolerance in several rice cultivars via multiple modulations of membrane sterols

Tadao Wagatsuma, Eriko Maejima, Toshihiro Watanabe, Tomonobu Toyomasu, Masaharu Kuroda, Toshiya Muranaka, Kiyoshi Ohyama, Akifumi Ishikawa, Masami Usui, Shahadat Hossain Khan, Hayato Maruyama, Keitaro Tawaraya, Yuriko Kobayashi and Hiroyuki Koyama

in Journal of Experimental Botany

Volume 69, issue 3, pages 567-577
Published in print January 2018 | ISSN: 0022-0957
Published online December 2017 | e-ISSN: 1460-2431 | DOI: https://dx.doi.org/10.1093/jxb/erx414
Dark conditions enhance aluminum tolerance in several rice cultivars via multiple modulations of membrane sterols

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Abstract

Aluminum-sensitive rice (Oryza sativa L.) cultivars showed increased Al tolerance under dark conditions, because less Al accumulated in the root tips (1 cm) under dark than under light conditions. Under dark conditions, the root tip concentration of total sterols, which generally reduce plasma membrane permeabilization, was higher in the most Al-sensitive japonica cultivar, Koshihikari (Ko), than in the most Al-tolerant cultivar, Rikuu-132 (R132), but the phospholipid content did not differ between the two. The Al treatment increased the proportion of stigmasterol (which has no ability to reduce membrane permeabilization) out of total sterols similarly in both cultivars under light conditions, but it decreased more in Ko under dark conditions. The carotenoid content in the root tip of Al-treated Ko was significantly lower under dark than under light conditions, indicating that isopentenyl diphosphate transport from the cytosol to plastids was decreased under dark conditions. HMG2 and HMG3 (encoding the key sterol biosynthetic enzyme 3-hydroxy-3-methylglutaryl CoA reductase) transcript levels in the root tips were enhanced under dark conditions. We suggest that the following mechanisms contribute to the increase in Al tolerance under dark conditions: inhibition of stigmasterol formation to retain membrane integrity; greater partitioning of isopentenyl diphosphate for sterol biosynthesis; and enhanced expression of HMGs to increase sterol biosynthesis.

Keywords: Al tolerance; carotenoid; dark conditions; HMG gene; rice; sterol; stigmasterol

Journal Article.  7061 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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