scholarly journals Ascorbate oxidation activates systemic defence against root-knot nematode Meloidogyne graminicola in rice

2020 ◽  
Vol 71 (14) ◽  
pp. 4271-4284 ◽  
Author(s):  
Richard Raj Singh ◽  
Bruno Verstraeten ◽  
Shahid Siddique ◽  
Adelahu Mekonene Tegene ◽  
Raimund Tenhaken ◽  
...  
Keyword(s):  
Ascorbic Acid ◽  
Oryza Sativa ◽  
Functional Role ◽  
Nematode Infection ◽  
Ascorbate Oxidase ◽  
Systemic Effects ◽  
Root Knot Nematode ◽  
Meloidogyne Graminicola ◽  
Shoot Tissue ◽  
Ethephon Treatment

Abstract Ascorbic acid (AA) is the major antioxidant buffer produced in the shoot tissue of plants. Previous studies on root-knot nematode (RKN; Meloidogyne graminicola)-infected rice (Oryza sativa) plants showed differential expression of AA-recycling genes, although their functional role was unknown. Our results confirmed increased dehydroascorbate (DHA) levels in nematode-induced root galls, while AA mutants were significantly more susceptible to nematode infection. External applications of ascorbate oxidase (AO), DHA, or reduced AA, revealed systemic effects of ascorbate oxidation on rice defence versus RKN, associated with a primed accumulation of H2O2 upon nematode infection. To confirm and further investigate these systemic effects, a transcriptome analysis was done on roots of foliar AO-treated plants, revealing activation of the ethylene (ET) response and jasmonic acid (JA) biosynthesis pathways in roots, which was confirmed by hormone measurements. Activation of these pathways by methyl-JA, or ethephon treatment can complement the susceptibility phenotype of the rice Vitamin C (vtc1) mutant. Experiments on the jasmonate signalling (jar1) mutant or using chemical JA/ET inhibitors confirm that the effects of ascorbate oxidation are dependent on both the JA and ET pathways. Collectively, our data reveal a novel pathway in which ascorbate oxidation induces systemic defence against RKNs.

Effect of nitrogen supply form on the invasion of rice roots by the root-knot nematode, Meloidogyne graminicola

Nematology ◽  
2013 ◽  
Vol 15 (4) ◽  
pp. 483-492 ◽  
Author(s):  
Jagadeesh Patil ◽  
Anthony J. Miller ◽  
Hari S. Gaur
Keyword(s):  
N Uptake ◽  
Calcium Nitrate ◽  
Nematode Infection ◽  
Nitrate Transport ◽  
Critical Periods ◽  
Transport Activity ◽  
Root Knot Nematode ◽  
Infected Control ◽  
Meloidogyne Graminicola ◽  
Important Pest

Rice is capable of taking up both nitrate (NO3−) and ammonical (NH4+) forms of nitrogen (N). It is largely grown under flooded cultivation when NH4+ is the main form of available soil N. The root knot nematode, Meloidogyne graminicola, can cause serious damage to rice crops and disturb N uptake and translocation. We have investigated if the N supply form can influence the susceptibility of rice to this important pest. Roots supplied with a 100-fold lower supply of calcium nitrate (0.1 mM Ca(NO3)2) showed a higher level of nematode infection as measured by the gall index. Plants supplied with 2.85 mM of Ca(NO3)2 were more infected compared with the same dose of ammonium nitrate (NH4NO3) or ammonium chloride (NH4Cl). 15NO3− influx studies showed significantly smaller uptake of nitrate in nematode-infected roots when compared with non-infected control plants. The electrophysiological studies showed that resting cell membrane potentials of nematode-infected plants were significantly smaller (less negative) than those of non-infected control rice. Furthermore, when the cellular responses to NO3− were compared, these also showed significantly smaller nitrate transport activity in nematode-infected roots (4.7 ± 1.2 mV) when compared with non-infected control plants (11.9 ± 3.4 mV). Taken together, the 15NO3− influx and electrophysiological measurements clearly showed that the root NO3− transport activity was severely decreased in nematode-infected roots. The results also show that regulation of NO3− concentration at critical periods of nematode infection of rice root can provide a non-nematicidal method of nematode management.

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