Ribeiro Carolina W, Korbes Ana Paula, Garighan Julio A, Jardim-Messeder Douglas, Carvalho Fabricio E L, Sousa Rachel H V, Caverzan Andreia, Teixeira Felipe K, Silveira Joaquim A G, Margis-Pinheiro Marcia
Programa de Pós-Graduação em Biologia Celular e Molecular, Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil; Departamento de Genética, Universidade Federal do Rio Grande do Sul, 91501-970, Porto Alegre, RS, Brazil.
Departamento de Genética, Universidade Federal do Rio Grande do Sul, 91501-970, Porto Alegre, RS, Brazil.
Plant Sci. 2017 Oct;263:55-65. doi: 10.1016/j.plantsci.2017.07.009. Epub 2017 Jul 13.
HO, which is continually produced by aerobic metabolism, is a cytotoxic molecule when in high levels. However, low levels can act as a signaling molecule able to regulate the expression of stress responses, senescence, programmed cell death, plant growth, and development. Ascorbate peroxidase (APX) enzyme plays an essential role in the control of intracellular HO levels. Here, the function of a gene encoding a peroxisomal APX (OsAPX4) from rice (Oryza sativa L.) was studied. OsAPX4 gene expression can be detected in roots and panicles, but the highest expression level occurs in leaves. Silencing of OsAPX4 and OsAPX3 expression in RNAiOsAPX4 did not affect the growth of plants under growth chamber conditions, but aging transgenic plants interestingly displayed an early senescence phenotype. Leaf fragments from silenced plants were also more sensitive to induced senescence conditions. RNAiOsAPX4 plants did not present detectable changes in intracellular HO levels, but biochemical analyses showed that transgenic plants displayed some decreased APX activity in the chloroplastic fraction. Also, the peroxisomal enzyme glycolate oxidase exhibited lower activity, whereas catalase activity was similar to non-transformed rice. The results imply that OsAPX4 gene has an important role in leaf senescence pathway mediated by ROS signaling.
过氧化氢（HO）由有氧代谢持续产生，当其处于高水平时是一种细胞毒性分子。然而，低水平的HO可以作为一种信号分子，能够调节应激反应、衰老、程序性细胞死亡、植物生长和发育的表达。抗坏血酸过氧化物酶（APX）在控制细胞内HO水平方面起着至关重要的作用。在此，对水稻（Oryza sativa L.）中一个编码过氧化物酶体APX（OsAPX4）的基因功能进行了研究。OsAPX4基因表达可在根和穗中检测到，但最高表达水平出现在叶片中。在RNAiOsAPX4中沉默OsAPX4和OsAPX3的表达在生长室条件下不影响植物生长，但有趣的是，衰老的转基因植物表现出早期衰老表型。来自沉默植株的叶片片段对诱导衰老条件也更敏感。RNAiOsAPX4植株在细胞内HO水平上未呈现可检测到的变化，但生化分析表明，转基因植株在叶绿体部分的APX活性有所降低。此外，过氧化物酶体酶乙醇酸氧化酶活性较低，而过氧化氢酶活性与未转化水稻相似。结果表明，OsAPX4基因在由ROS信号介导的叶片衰老途径中具有重要作用。
