The glucosinolate-myrosinase system is a well-known plant chemical defence system. Two functional myrosinase-encoding genes, THIOGLUCOSIDASE 1 (TGG1) and THIOGLUCOSIDASE 2 (TGG2), express in aerial tissues of Arabidopsis. TGG1 expresses in guard cells (GCs) and is also a highly abundant protein in GCs. Recently, by studying wild type (WT), tgg single, and double mutants, we showed a novel association between the glucosinolate-myrosinase system defence system, and a physical barrier, the cuticle. In the current study, using imaging techniques, we further analysed stomata and ultrastructure of GCs of WT, tgg1, tgg2 single, and tgg1 tgg2 double mutants. The tgg mutants showed distinctive features of GCs. The GCs of tgg1 and tgg1 tgg2 mutants showed vacuoles that had less electron-dense granular material. Both tgg single mutants had bigger stomata complexes. The WT and tgg mutants also showed variations for cell wall, chloroplasts, and starch grains of GCs. Abscisic acid (ABA)-treated stomata showed that the stomatal aperture was reduced in tgg1 single and tgg1 tgg2 double mutants. The data provides a basis to perform comprehensive further studies to find physiological and molecular mechanisms associated with ultrastructure differences in tgg mutants. We speculate that the absence of myrosinase alters the endogenous chemical composition, hence affecting the physical structure of plants and the plants’ physical defence barriers.

中文翻译：

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拟南芥硫代葡萄糖苷酶 (tgg) 突变体保卫细胞的成像进一步将植物化学防御系统与物理防御屏障联系起来


芥子油苷-黑芥子酶系统是众所周知的植物化学防御系统。两种功能性黑芥子酶编码基因，硫葡萄糖苷酶 1 ( TGG1 ) 和硫葡萄糖苷酶 2 ( TGG2 )，在拟南芥地上组织中表达。 TGG1在保卫细胞 (GC) 中表达，也是 GC 中高度丰富的蛋白质。最近，通过研究野生型（WT）、 tgg单突变体和双突变体，我们展示了芥子油苷-黑芥子酶系统防御系统与物理屏障（角质层）之间的新关联。在本研究中，我们利用成像技术进一步分析了WT、 tgg1 、 tgg2单突变体和tgg1 tgg2双突变体GC的气孔和超微结构。 tgg突变体表现出 GC 的独特特征。 tgg1和tgg1 tgg2突变体的 GC 显示出具有较少电子致密颗粒材料的液泡。两种tgg单突变体都有更大的气孔复合体。 WT 和tgg突变体还显示出 GC 的细胞壁、叶绿体和淀粉粒的变化。脱落酸（ABA）处理的气孔显示， tgg1单突变体和tgg1 tgg2双突变体的气孔孔径减小。这些数据为进行全面的进一步研究提供了基础，以寻找与tgg突变体超微结构差异相关的生理和分子机制。我们推测黑芥子酶的缺失会改变内源化学成分，从而影响植物的物理结构和植物的物理防御屏障。