Dark conditions enhance aluminum tolerance in several rice cultivars via multiple modulations of membrane sterols. (23rd December 2017)

• Record Type: Journal Article
• Authors: Wagatsuma, Tadao; Maejima, Eriko; Watanabe, Toshihiro; Toyomasu, Tomonobu; Kuroda, Masaharu; Muranaka, Toshiya; Ohyama, Kiyoshi; Ishikawa, Akifumi; Usui, Masami; Hossain Khan, Shahadat; Maruyama, Hayato; Tawaraya, Keitaro; Kobayashi, Yuriko; Koyama, Hiroyuki
• Is Part Of: Journal of experimental botany. Volume 69:Number 3(2018)
• Page Start: 567
• Page End: 577
• Publication Date: 2017-12-23
• Subjects: Al tolerance -- carotenoid -- dark conditions -- HMG gene -- rice -- sterol -- stigmasterol; Botany -- Periodicals; Botany, Experimental -- Periodicals; Plant physiology -- Periodicals; 580
• DOI: 10.1093/jxb/erx414
• Languages: English
• ISSNs: 0022-0957

Abstract

Abstract : Aluminum tolerance of aluminum-sensitive rice was enhanced under darkness by multiple changes in membrane sterols: decreased stigmasterol, increased precursor partitioning for sterols biosynthesis, and increased expression of HMG genes. 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 HMG s to increase sterol biosynthesis.