Singh Richard Raj, Pajar Jessil Ann, Audenaert Kris, Kyndt Tina
Department of Biotechnology, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium.
Department of Plants and Crops, Ghent University, Ghent, Belgium.
Front Plant Sci. 2021 Aug 11;12:713870. doi: 10.3389/fpls.2021.713870. eCollection 2021.
Anticipating an increased ecological awareness, scientists have been exploring new strategies to reduce the use of chemical pesticides to control pests and diseases. Triggering the intrinsic plant defense system is one of the promising strategies to reduce yield loss by pathogenic organisms, such as nematodes. Ascorbate oxidase (AO) enzyme plays an important role in plant defense by regulating the apoplastic ascorbate/dehydroascorbate (DHA) ratio the ascorbate oxidation process. Ascorbate oxidation is known to induce systemic resistance in rice against parasitic root-knot nematodes (RKN). Here, we sought to evaluate if AO- or DHA-induced resistance (IR) against RKN involves activation of the phenylpropanoid pathway and whether this IR phenotype has potential effects on growth of rice seedlings under stressed and unstressed conditions. Our results show that AO/DHA-IR against these parasitic nematodes is dependent on activation of phenylalanine ammonia lyase (PAL). However, application of reduced ascorbic acid (AA) did not induce this response. Gene expression analysis qRT-PCR showed that and are highly expressed in AO/DHA-sprayed nematode-infected roots and PAL-activity measurements confirmed that AO/DHA spraying triggers the plants for primed activation of this enzyme upon nematode infection. AO/DHA-IR is not effective in plants sprayed with a chemical PAL inhibitor confirming that AO/DHA-induced resistance is dependent on PAL activity. Improved plant growth and low nematode infection in AO/DHA-sprayed plants was found to be correlated with an increase in shoot chlorophyll fluorescence (Fv/Fm), chlorophyll index (ChlIdx), and modified anthocyanin reflection index which were proven to be good above-ground parameters for nematode infestation. A detailed growth analysis confirmed the improved growth of AO/DHA-treated plants under nematode-infected conditions. Taken together, our results indicate that ascorbate oxidation enhances the phenylpropanoid-based response to nematode infection and leads to a tolerance phenotype in treated rice plants.
鉴于人们对生态意识的日益增强，科学家们一直在探索新的策略，以减少化学农药的使用来控制病虫害。触发植物内在防御系统是减少线虫等致病生物造成产量损失的一种有前景的策略。抗坏血酸氧化酶（AO）通过调节质外体抗坏血酸/脱氢抗坏血酸（DHA）比值——抗坏血酸氧化过程，在植物防御中发挥重要作用。已知抗坏血酸氧化可诱导水稻对寄生根结线虫（RKN）产生系统抗性。在此，我们试图评估AO或DHA诱导的对RKN的抗性（IR）是否涉及苯丙烷途径的激活，以及这种IR表型在胁迫和非胁迫条件下对水稻幼苗生长是否有潜在影响。我们的结果表明，AO/DHA对这些寄生线虫的抗性取决于苯丙氨酸解氨酶（PAL）的激活。然而，施用还原型抗坏血酸（AA）并未诱导这种反应。基因表达分析——定量逆转录聚合酶链反应（qRT-PCR）表明，[具体基因]在AO/DHA喷洒的线虫感染根中高度表达，PAL活性测量证实AO/DHA喷洒会在植物受到线虫感染时触发该酶的预激活。用化学PAL抑制剂喷洒的植物中AO/DHA-IR无效，这证实了AO/DHA诱导的抗性取决于PAL活性。在AO/DHA喷洒的植物中发现改善的植物生长和低线虫感染与地上部叶绿素荧光（Fv/Fm）、叶绿素指数（ChlIdx）和改良花青素反射指数的增加相关，这些被证明是线虫侵染的良好地上部参数。详细的生长分析证实了AO/DHA处理的植物在受线虫感染条件下生长得到改善。综上所述，我们的结果表明抗坏血酸氧化增强了基于苯丙烷途径对线虫感染的反应，并导致处理过的水稻植株出现耐受表型。
