Instituto de Bioquímica Vegetal y Fotosíntesis, Consejo Superior de Investigaciones Científicas and Universidad de Sevilla, Avenida Américo Vespucio, 49, Sevilla 41092, Spain.
Plant Cell Physiol. 2018 May 1;59(5):1072-1083. doi: 10.1093/pcp/pcy047.
In Arabidopsis thaliana, cyanide is produced concomitantly with ethylene biosynthesis and is mainly detoxified by the ß-cyanoalanine synthase CAS-C1. In roots, CAS-C1 activity is essential to maintain a low level of cyanide for proper root hair development. Root hair elongation relies on polarized cell expansion at the growing tip, and we have observed that CAS-C1 locates in mitochondria and accumulates in root hair tips during root hair elongation, as shown by observing the fluorescence in plants transformed with the translational construct ProC1:CASC1-GFP, containing the complete CAS-C1 gene fused to green fluorescent protein (GFP). Mutants in the SUPERCENTIPEDE (SCN1) gene, that regulate the NADPH oxidase gene ROOT HAIR DEFECTIVE 2 (RHD2)/AtrbohC, are affected at the very early steps of the development of root hair that do not elongate and do not show a preferential localization of the GFP accumulation in the tips of the root hair primordia. Root hairs of mutants in CAS-C1 or RHD2/AtrbohC, whose protein product catalyzes the generation of ROS and the Ca2+ gradient, start to grow out correctly, but they do not elongate. Genetic crosses between the cas-c1 mutant and scn1 or rhd2 mutants were performed, and the detailed phenotypic and molecular characterization of the double mutants demonstrates that scn1 mutation is epistatic to cas-c1 and cas-c1 is epistatic to rhd2 mutation, indicating that CAS-C1 acts in early steps of the root hair development process. Moreover, our results show that the role of CAS-C1 in root hair elongation is independent of H2O2 production and of a direct NADPH oxidase inhibition by cyanide.
在拟南芥中，氰化物与乙烯生物合成同时产生，主要通过β-氰基丙氨酸合酶 CAS-C1 解毒。在根中，CAS-C1 活性对于维持低水平的氰化物以促进正常的根毛发育是必不可少的。根毛伸长依赖于生长尖端的极化细胞扩展，我们观察到 CAS-C1 位于线粒体中，并在根毛伸长过程中在根毛尖端积累，这是通过观察转化植物中 ProC1:CASC1-GFP 翻译构建体的荧光来证明的，该构建体包含与绿色荧光蛋白（GFP）融合的完整 CAS-C1 基因。SUPERCENTIPEDE (SCN1) 基因的突变体，调节 NADPH 氧化酶基因 ROOT HAIR DEFECTIVE 2 (RHD2)/AtrbohC，在根毛伸长的早期阶段受到影响，根毛不会伸长，并且 GFP 积累在根毛原基的尖端没有优先定位。CAS-C1 或 RHD2/AtrbohC 突变体的根毛开始正确生长，但不会伸长，其蛋白质产物催化 ROS 和 Ca2+梯度的产生。在 cas-c1 突变体和 scn1 或 rhd2 突变体之间进行了遗传杂交，并且双突变体的详细表型和分子特征表明，scn1 突变是 cas-c1 的上位性，而 cas-c1 是 rhd2 突变的上位性，表明 CAS-C1 作用于根毛发育过程的早期步骤。此外，我们的结果表明，CAS-C1 在根毛伸长中的作用独立于 H2O2 的产生和氰化物对 NADPH 氧化酶的直接抑制。
