Ascorbate Oxidase Induces Systemic Resistance in Sugar Beet Against Cyst Nematode Heterodera schachtii

Abstract

Ascorbate oxidase (AO) is an enzyme involved in catalyzing the oxidation of apoplastic ascorbic acid (AA) to dehydroascorbic acid (DHA). In this research, the potential of AO spraying to induce systemic resistance was demonstrated in the interaction between sugar beet root and cyst nematode Heterodera schachtii and the mechanism was elucidated. Plant bioassays showed that roots of AO-sprayed plants were infested by a significantly lower number of females and cysts when compared with mock-sprayed control plants. Hormone measurements showed an elevated level of jasmonic acid (JA) salicylic acid (SA) and ethylene (ET) in the roots of AO-sprayed plants, with a dynamic temporal pattern of activation. Experiments with chemical inhibitors showed that AOinduced systemic resistance is partially dependent on the JA, ET and SA pathways. Biochemical analyses revealed a primed accumulation of hydrogen peroxide (H 2 O 2), and phenylalanine ammonia lyase (PAL) activity in the roots of AO-sprayed plants upon infection by cyst nematodes. In conclusion, our data shows that AO works as an effective systemic defense priming agent in sugar beet against cyst nematode infection, through activation of multiple basal plant defense pathways.

The miR528-AO Module Confers Enhanced Salt Tolerance in Rice by Modulating the Ascorbic Acid and Abscisic Acid Metabolism and ROS Scavenging

“…Contrarily, AO overexpression triggered the accumulation of basal ROS, which had a protective role in rice antiviral defense . In addition, exogenous spraying of AO strongly enhanced plant nematode resistance in sugar beet . It seems that AO functions in totally contradictory ways on defense against abiotic and biotic stresses.…”

“…9 In addition, exogenous spraying of AO strongly enhanced plant nematode resistance in sugar beet. 66 It seems that AO functions in totally contradictory ways on defense against abiotic and biotic stresses. Accordingly, AO is supposed to be a mysterious enzyme, whose various roles need further exploration.…”

Induced Resistance by Ascorbate Oxidation Involves Potentiating of the Phenylpropanoid Pathway and Improved Rice Tolerance to Parasitic Nematodes

“…Induced resistance against nematodes seems generally correlated with activation of the phenylpropanoid pathway. For example in Singh et al (2019Singh et al ( , 2020a, systemic activation of the phenylpropanoid pathway in response to application of COS-OGA in rice or AO in sugar beet was observed to be correlated with induced resistance to parasitic root-knot and cyst nematodes. Similarly, Huang et al (2016) showed that thiamine-induced resistance against M. graminicola in rice involved lignin deposition in plant roots, and this correlated with enhanced transcription of OsPAL1 and OsC4H, two genes involved in the phenylpropanoid pathway.…”

Identification of the Complex Interplay Between Nematode-Related lncRNAs and Their Target Genes in Glycine max L.

“…Likewise, the functional annotation of DEGs in sweet potato (Lee et al, 2021) and in cotton (Kumar et al, 2019) demonstrated "response to salicylic acid" as the key enriched BP against nematode infestation. The role of JA, as another plant signaling compound, has been investigated upon nematode infection in different plant species (Hamamouch et al, 2011;Fan et al, 2015;Regis, 2015;Singh et al, 2020). JA-mediated tolerance against RKN infection is reported through alteration in the photosynthetic and antioxidative defense mechanisms in tomato plants (Bali et al, 2018).…”