Li Rong, Xin Shan, Tao Chengcheng, Jin Xiang, Li Hongbin
College of Life Sciences, Key laboratory of Agrobiotechnology, Shihezi University, Shihezi 832003, China.
Institute of Tropical Biosciences and Biotechnology, Chinese Academy of Tropical Agricultural Sciences, Haikou 571101, China.
Int J Mol Sci. 2017 Jun 23;18(7):1346. doi: 10.3390/ijms18071346.
Ascorbate oxidase (AO) plays an important role in cell growth through the modulation of reduction/oxidation (redox) control of the apoplast. Here, a cotton () apoplastic ascorbate oxidase gene () was obtained from fast elongating fiber tissues. GhAO1 belongs to the multicopper oxidase (MCO) family and includes a signal peptide and several transmembrane regions. Analyses of quantitative real-time polymerase chain reaction (QRT-PCR) and enzyme activity showed that was expressed abundantly in 15-day post-anthesis (dpa) wild-type (WT) fibers in comparison with () mutant ovules. Subcellular distribution analysis in onion cells demonstrated that GhAO1 is localized in the cell wall. In transgenic tobacco bright yellow-2 (BY-2) cells with ectopic overexpression of , the enhancement of cell growth with 1.52-fold increase in length versus controls was indicated, as well as the enrichment of both total ascorbate in whole-cells and dehydroascorbate acid (DHA) in apoplasts. In addition, promoted activities of AO and monodehydroascorbate reductase (MDAR) in apoplasts and dehydroascorbate reductase (DHAR) in whole-cells were displayed in transgenic tobacco BY-2 cells. Accumulation of H₂O₂, and influenced expressions of Ca channel genes with the activation of and and the suppression of were also demonstrated in transgenic tobacco BY-2 cells. Finally, significant induced expression of the tobacco gene in WT BY-2 cells under indole-3-acetic acid (IAA) treatment appeared; however, the sensitivity of the gene expression to IAA disappeared in transgenic BY-2 cells, revealing that the regulated expression of the gene is under the control of IAA. Taken together, these results provide evidence that plays an important role in fiber cell elongation and may promote cell growth by generating the oxidation of apoplasts, via the auxin-mediated signaling pathway.
抗坏血酸氧化酶（AO）通过调节质外体的氧化还原控制在细胞生长中发挥重要作用。在此，从快速伸长的纤维组织中获得了一个棉花（）质外体抗坏血酸氧化酶基因（）。GhAO1属于多铜氧化酶（MCO）家族，包含一个信号肽和几个跨膜区域。定量实时聚合酶链反应（QRT-PCR）和酶活性分析表明，与（）突变胚珠相比，该基因在开花后15天（dpa）的野生型（WT）纤维中大量表达。洋葱细胞中的亚细胞定位分析表明，GhAO1定位于细胞壁。在异位过表达的转基因烟草亮黄-2（BY-2）细胞中，表明细胞生长增强，长度比对照增加了1.52倍，同时全细胞中的总抗坏血酸和质外体中的脱氢抗坏血酸（DHA）也有所富集。此外，转基因烟草BY-2细胞中质外体中的AO和单脱氢抗坏血酸还原酶（MDAR）以及全细胞中的脱氢抗坏血酸还原酶（DHAR）的活性均得到促进。转基因烟草BY-2细胞中还证实了H₂O₂的积累，以及对Ca通道基因表达的影响，表现为和的激活以及的抑制。最后，在吲哚-3-乙酸（IAA）处理下，野生型BY-2细胞中烟草基因出现明显的诱导表达；然而，转基因BY-2细胞中该基因表达对IAA的敏感性消失，这表明该基因的调控表达受IAA控制。综上所述，这些结果提供了证据，表明在纤维细胞伸长中起重要作用，并且可能通过生长素介导的信号通路产生质外体氧化来促进细胞生长。
