Cytochrome b5 Reductase 1 Triggers Serial Reactions that Lead to Iron Uptake in Plants

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• 作者：Young Jun Oh¹ ; Hanul Kim² ; Sung Hee Seo³ ; Bae Geun Hwang⁴ ; Yoon Seok Chang³ ; Junho Lee² ; Dong Wook Lee¹ ; Eun Ju Sohn¹ ; Sang Joon Lee⁴ ; Youngsook Lee¹ ; ² ; Inhwan Hwang¹ ; ² ; ^{ihhwang@postech.ac.kr" class="auth_mail" title="E-mail the corresponding author}
• 关键词：cytochrome b5 reductase 1 (CBR1) ; unsaturated fatty acids ; iron (Fe) uptake ; H+-ATPase
• 刊名：Molecular Plant
• 出版年：2016
• 出版时间：4 April 2016
• 年：2016
• 卷：9
• 期：4
• 页码：501-513
• 全文大小：2365 K

文摘

Rhizosphere acidification is essential for iron (Fe) uptake into plant roots. Plasma membrane (PM) H⁺-ATPases play key roles in rhizosphere acidification. However, it is not fully understood how PM H⁺-ATPase activity is regulated to enhance root Fe uptake under Fe-deficient conditions. Here, we present evidence that cytochrome b5 reductase 1 (CBR1) increases the levels of unsaturated fatty acids, which stimulate PM H⁺-ATPase activity and thus lead to rhizosphere acidification. CBR1-overexpressing (CBR1-OX) Arabidopsis thaliana plants had higher levels of unsaturated fatty acids (18:2 and 18:3), higher PM H⁺-ATPase activity, and lower rhizosphere pH than wild-type plants. By contrast, cbr1 loss-of-function mutant plants showed lower levels of unsaturated fatty acids and lower PM H⁺-ATPase activity but higher rhizosphere pH. Reduced PM H⁺-ATPase activity in cbr1 could be restored in vitro by addition of unsaturated fatty acids. Transcript levels of CBR1, fatty acids desaturase2 (FAD2), and fatty acids desaturase3 (FAD3) were increased under Fe-deficient conditions. We propose that CBR1 has a crucial role in increasing the levels of unsaturated fatty acids, which activate the PM H⁺-ATPase and thus reduce rhizosphere pH. This reaction cascade ultimately promotes root Fe uptake.