Sherwood Patrick, Villari Caterina, Capretti Paolo, Bonello Pierluigi
Department of Plant Pathology, The Ohio State University, Columbus, OH 43210 , USA
Department of Plant Pathology, The Ohio State University, Columbus, OH 43210 , USA.
Tree Physiol. 2015 May;35(5):549-62. doi: 10.1093/treephys/tpv026. Epub 2015 Apr 21.
Plants experiencing drought stress are frequently more susceptible to pathogens, likely via alterations in physiology that create favorable conditions for pathogens. Common plant responses to drought include the production of reactive oxygen species (ROS) and the accumulation of free amino acids (AAs), particularly proline. These same phenomena also frequently occur during pathogenic attack. Therefore, drought-induced perturbations in AA and ROS metabolism could potentially contribute to the observed enhanced susceptibility. Furthermore, nitrogen (N) availability can influence AA accumulation and affect plant resistance, but its contributions to drought-induced susceptibility are largely unexplored. Here we show that drought induces accumulation of hydrogen peroxide (H2O2) in Austrian pine (Pinus nigra Arnold) shoots, but that shoot infection by the blight and canker pathogen Diplodia sapinea (Fr.) Fuckel leads to large reductions in H2O2 levels in droughted plants. In in vitro assays, H2O2 was toxic to D. sapinea, and the fungus responded to this oxidative stress by increasing catalase and peroxidase activities, resulting in substantial H2O2 degradation. Proline increased in response to drought and infection when examined independently, but unlike all other AAs, proline further increased in infected shoots of droughted trees. In the same tissues, the proline precursor, glutamate, decreased significantly. Proline was found to protect D. sapinea from H2O2 damage, while also serving as a preferred N source in vitro. Fertilization increased constitutive and drought-induced levels of some AAs, but did not affect plant resistance. A new model integrating interactions of proline and H2O2 metabolism with drought and fungal infection of plants is proposed.
遭受干旱胁迫的植物通常更容易受到病原体的侵害，这可能是通过生理变化为病原体创造了有利条件。植物对干旱的常见反应包括活性氧（ROS）的产生和游离氨基酸（AAs）的积累，尤其是脯氨酸。这些相同的现象在病原体攻击期间也经常发生。因此，干旱引起的氨基酸和ROS代谢紊乱可能会导致观察到的易感性增强。此外，氮（N）的有效性会影响氨基酸的积累并影响植物抗性，但它对干旱诱导的易感性的贡献在很大程度上尚未得到探索。在这里，我们表明干旱会诱导奥地利黑松（Pinus nigra Arnold）嫩枝中过氧化氢（H2O2）的积累，但枯萎和溃疡病原体松色二孢（Diplodia sapinea (Fr.) Fuckel）对干旱植物嫩枝的感染会导致H2O2水平大幅降低。在体外试验中，H2O2对松色二孢有毒，该真菌通过增加过氧化氢酶和过氧化物酶活性来应对这种氧化应激，从而导致大量H2O2降解。单独检测时，脯氨酸在干旱和感染时都会增加，但与所有其他氨基酸不同的是，脯氨酸在干旱树木的受感染嫩枝中进一步增加。在相同组织中，脯氨酸前体谷氨酸显著减少。发现脯氨酸可保护松色二孢免受H2O2损伤，同时在体外也是一种首选的氮源。施肥增加了一些氨基酸的组成型和干旱诱导水平，但不影响植物抗性。我们提出了一个新的模型，该模型整合了脯氨酸和H2O2代谢与植物干旱和真菌感染之间的相互作用。
