Li Meng, Sack Fred D
Department of Botany, University of British Columbia, Vancouver V6T 1Z4, Canada.
Department of Botany, University of British Columbia, Vancouver V6T 1Z4, Canada
Plant Cell. 2014 Oct;26(10):4053-66. doi: 10.1105/tpc.114.129726. Epub 2014 Oct 10.
Crucifer shoots harbor a glucosinolate-myrosinase system that defends against insect predation. Arabidopsis thaliana myrosinase (thioglucoside glucohydrolase [TGG]) accumulates in stomata and in myrosin idioblasts (MIs). This work reports that the basic helix-loop-helix transcription factor FAMA that is key to stomatal development is also expressed in MIs. The loss of FAMA function abolishes MI fate as well as the expression of the myrosinase genes TGG1 and TGG2. MI cells have previously been reported to be located in the phloem. Instead, we found that MIs arise from the ground meristem rather than provascular tissues and thus are not homologous with phloem. Moreover, MI patterning and morphogenesis are abnormal when the function of the ARF-GEF gene GNOM is lost as well as when auxin efflux and vesicular trafficking are chemically disrupted. Stomata and MI cells constitute part of a wider system that reduces plant predation, the so-called "mustard oil bomb," in which vacuole breakage in cells harboring myrosinase and glucosinolate yields a brew toxic to many animals, especially insects. This identification of the gene that confers the fate of MIs, as well as stomata, might facilitate the development of strategies for engineering crops to mitigate predation.
十字花科植物的嫩枝含有一个芥子油苷-黑芥子酶系统，可抵御昆虫捕食。拟南芥黑芥子酶（硫代葡萄糖苷葡萄糖水解酶 [TGG]）在气孔和黑芥子酶异细胞（MIs）中积累。这项研究报告称，对气孔发育至关重要的碱性螺旋-环-螺旋转录因子FAMA也在MIs中表达。FAMA功能的丧失消除了MI的命运以及黑芥子酶基因TGG1和TGG2的表达。此前有报道称MI细胞位于韧皮部。相反，我们发现MIs起源于基本分生组织而非原形成层组织，因此与韧皮部不同源。此外，当ARF-GEF基因GNOM的功能丧失以及生长素外流和囊泡运输受到化学破坏时，MI的模式形成和形态发生会出现异常。气孔和MI细胞构成了一个更广泛的减少植物被捕食的系统的一部分，即所谓的“芥子油炸弹”，其中含有黑芥子酶和芥子油苷的细胞中的液泡破裂会产生一种对许多动物，尤其是昆虫有毒的混合物。对赋予MIs以及气孔命运的基因的鉴定，可能有助于制定工程作物以减轻捕食的策略。
