Institute of Molecular Physiology and Biotechnology of Plants (IMBIO), University of Bonn, Karlrobert-Kreiten-Straße 13, 53115, Bonn, Germany.
Institute of Cellular and Molecular Botany (IZMB), University of Bonn, Kirschallee 1, 53115, Bonn, Germany.
Plant J. 2019 May;98(4):727-744. doi: 10.1111/tpj.14269. Epub 2019 Mar 18.
Waxes are components of the cuticle covering the aerial organs of plants. Accumulation of waxes has previously been associated with protection against water loss, therefore contributing to drought tolerance. However, not much information is known about the function of individual wax components during water deficit. We studied the role of wax ester synthesis during drought. The wax ester load on Arabidopsis leaves and stems was increased during water deficiency. Expression of three genes, WSD1, WSD6 and WSD7 of the wax ester synthase/diacylglycerol acyltransferase (WS/DGAT or WSD) family was induced during drought, salt stress and abscisic acid treatment. WSD1 has previously been identified as the major wax ester synthase of stems. wsd1 mutants have shown reduced wax ester coverage on leaves and stems during normal or drought condition, while wax ester loads of wsd6, wsd7 and of the wsd6wsd7 double mutant were unchanged. The growth and relative water content of wsd1 plants were compromised during drought, while leaf water loss of wsd1 was increased. Enzyme assays with recombinant proteins expressed in insect cells revealed that WSD6 and WSD7 contain wax ester synthase activity, albeit with different substrate specificity compared with WSD1. WSD6 and WSD7 localize to the endoplasmic reticulum (ER)/Golgi. These results demonstrated that WSD1 is involved in the accumulation of wax esters during drought, while WSD6 and WSD7 might play other specific roles in wax ester metabolism during stress.
蜡质是覆盖植物气生器官的角质层的组成部分。以前曾认为蜡质的积累与防止水分流失有关，因此有助于耐旱性。然而，关于水分亏缺时个别蜡质成分的功能知之甚少。我们研究了蜡酯合成在干旱期间的作用。在水分不足时，拟南芥叶片和茎上的蜡酯负荷增加。蜡酯合酶/二酰基甘油酰基转移酶（WS/DGAT 或 WSD）家族的三个基因 WSD1、WSD6 和 WSD7 的表达在干旱、盐胁迫和脱落酸处理期间被诱导。WSD1 以前被鉴定为茎的主要蜡酯合酶。wsd1 突变体在正常或干旱条件下叶片和茎上的蜡酯覆盖减少，而 wsd6、wsd7 和 wsd6wsd7 双突变体的蜡酯负荷不变。在干旱期间，wsd1 植物的生长和相对含水量受损，而 wsd1 的叶片水分损失增加。用昆虫细胞表达的重组蛋白进行的酶测定表明，WSD6 和 WSD7 具有蜡酯合酶活性，尽管与 WSD1 相比具有不同的底物特异性。WSD6 和 WSD7 定位于内质网（ER）/高尔基体。这些结果表明，WSD1 参与干旱期间蜡酯的积累，而 WSD6 和 WSD7 可能在应激期间蜡酯代谢中发挥其他特定作用。
