Diaz-Vivancos P, Rubio M, Mesonero V, Periago P M, Barceló A Ros, Martínez-Gómez P, Hernández J A
Department of Plant Breeding. CEBAS-CSIC, PO Box 164, E-30100 Espinardo, Murcia, Spain.
J Exp Bot. 2006;57(14):3813-24. doi: 10.1093/jxb/erl138. Epub 2006 Oct 16.
This work describes, for the first time, the changes taking place in the antioxidative system of the leaf apoplast in response to plum pox virus (PPV) in different Prunus species showing different susceptibilities to PPV. The presence of p-hydroxymercuribenzoic acid (pHMB)-sensitive ascorbate peroxidase (APX) (class I APX) and pHMB-insensitive APX (class III APX), superoxide dismutase (SOD), peroxidase (POX), NADH-POX, and polyphenoloxidase (PPO) was described in the apoplast from both peach and apricot leaves. PPV infection produced different changes in the antioxidant system of the leaf apoplast from the Prunus species, depending on their susceptibility to the virus. In leaves of the very susceptible peach cultivar GF305, PPV brought about an increase in class I APX, POX, NADH-POX, and PPO activities. In the susceptible apricot cultivar Real Fino, PPV infection produced a decrease in apoplastic POX and SOD activities, whereas a strong increase in PPO was observed. However, in the resistant apricot cultivar Stark Early Orange, a rise in class I APX as well as a strong increase in POX and SOD activities was noticed in the apoplastic compartment. Long-term PPV infection produced an oxidative stress in the apoplastic space from apricot and peach plants, as observed by the increase in H2O2 contents in this compartment. However, this increase was much higher in the PPV-susceptible plants than in the resistant apricot cultivar. Only in the PPV-susceptible apricot and peach plants was the increase in apoplastic H2O2 levels accompanied by an increase in electrolyte leakage. No changes in the electrolyte leakage were observed in the PPV-inoculated resistant apricot leaves, although a 42% increase in the apoplastic H2O2 levels was produced. Two-dimensional electrophoresis analyses revealed that the majority of the polypeptides in the apoplastic fluid had isoelectric points in the range of pI 4-6. The identification of proteins using MALDI-TOF (matrix-assisted laser desorption/ionization-time of flight) and peptide mass fingerprinting analyses showed the induction of a thaumatin-like protein as well as the decrease of mandelonitrile lyase in peach apoplast due to PPV infection. However, most of the selected polypeptides showed no homology with known proteins. This fact emphasizes that, at least in Prunus, most of the functions of the apoplastic space remain unknown. It is concluded that long-term PPV infection produced an oxidative stress in the leaf apoplast, contributing to the deleterious effects produced by PPV infection in leaves of inoculated, susceptible Prunus plants.
这项研究首次描述了不同李属物种的叶片质外体抗氧化系统在应对李痘病毒（PPV）时发生的变化，这些物种对PPV的易感性不同。在桃和杏叶片的质外体中发现了对对羟基汞苯甲酸（pHMB）敏感的抗坏血酸过氧化物酶（APX）（I类APX）和对pHMB不敏感的APX（III类APX）、超氧化物歧化酶（SOD）、过氧化物酶（POX）、NADH-POX和多酚氧化酶（PPO）。PPV感染使李属物种叶片质外体的抗氧化系统产生了不同变化，这取决于它们对该病毒的易感性。在极易感的桃品种GF305的叶片中，PPV导致I类APX、POX、NADH-POX和PPO活性增加。在易感的杏品种Real Fino中，PPV感染使质外体POX和SOD活性降低，而PPO活性则大幅增加。然而，在抗性杏品种Stark Early Orange中，质外体部分的I类APX增加，POX和SOD活性也大幅增加。长期的PPV感染在杏和桃植株的质外体空间产生了氧化应激，这可通过该部分H2O2含量的增加来观察到。然而，这种增加在PPV易感植株中比在抗性杏品种中要高得多。只有在PPV易感的杏和桃植株中，质外体H2O2水平的增加伴随着电解质渗漏的增加。在接种了PPV的抗性杏叶片中未观察到电解质渗漏的变化，尽管质外体H2O2水平增加了42%。二维电泳分析表明，质外体流体中的大多数多肽的等电点在pI 4-6范围内。使用基质辅助激光解吸/电离飞行时间（MALDI-TOF）和肽质量指纹分析对蛋白质进行鉴定，结果显示由于PPV感染，桃质外体中类甜蛋白样蛋白被诱导，而扁桃腈裂解酶减少。然而，大多数选定的多肽与已知蛋白质没有同源性。这一事实强调，至少在李属中，质外体空间的大多数功能仍然未知。研究得出结论，长期的PPV感染在叶片质外体中产生了氧化应激，这促成了PPV感染对接种的易感李属植物叶片产生的有害影响。
