Abstract
In plant immune responses, reactive oxygen species (ROS) act as signaling molecules that activate defense pathways against pathogens, especially following resistance (R) gene-mediated pathogen recognition. Glutathione (GSH), an antioxidant and redox regulator, participates in the removal of hydrogen peroxide (H2O2). However, the mechanism of GSH-mediated H2O2 generation in soybeans (Glycine max (L.) Merr.) that are resistant to the soybean cyst nematode (SCN; Heterodera glycines Ichinohe) remains unclear. To elucidate this underlying relationship, the feeding of race 3 of H. glycines with resistant cultivars, Peking and PI88788, was compared with that on a susceptible soybean cultivar, Williams 82. After 5, 10, and 15 days of SCN infection, we quantified γ-glutamylcysteine (γ-EC) and (homo)glutathione ((h)GSH), and a gene expression analysis showed that GSH metabolism in resistant cultivars differed from that in susceptible soybean roots. ROS accumulation was examined both in resistant and susceptible roots upon SCN infection. The time of intense ROS generation was related to the differences of resistance mechanisms in Peking and PI88788. ROS accumulation that was caused by the (h)GSH depletion-arrested nematode development in susceptible Williams 82. These results suggest that (h)GSH metabolism in resistant soybeans plays a key role in the regulation of ROS-generated signals, leading to resistance against nematodes.
Highlights
The soybean (Glycine max (L.) Merr.) has been regarded as the “golden bean” or “miracle bean” [1], and is an important crop that provides a sustainable source of protein and oil worldwide
It is clear that the changes in related substances in the initiation of processes of different resistance reactions are important to the elucidation of the mechanism of soybean resistance and the promotion of the breeding of resistant soybean cultivars
We further demonstrated that (h)GSH deficiency led to a strongly delay in nematode development and oxidative burst. (h)GSH is considered a major antioxidant and is inter-linked with oxidants, such as (O2−) and H2O2, which are present inside cells, especially under stress conditions [49,50]
Summary
The soybean (Glycine max (L.) Merr.) has been regarded as the “golden bean” or “miracle bean” [1], and is an important crop that provides a sustainable source of protein and oil worldwide. The hypersensitivity reaction (HR), a typical programmed cell death, is induced to block the spread of pathogens in the host plants after avirulent pathogen invasion [27] This is associated with the modulation of the enzymatic activities that are involved in the neutralization of ROS production in interactions between resistant tomatoes and root-knot nematode (RKN) [28,29]. Its contributions to the tolerance to heavy metals, pathogens, nematode infection, salinity, and drought have been well documented [36,37,38,39] Under such conditions, plants generally produce GSH, which acts as an antioxidant and redox regulator by combating ROS [40]. The timing of the (h)GSH–H2O2 interaction in different resistant cultivars is a consequence of resistance or a hallmark of blocking successful nematode development
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