Abstract
Red light (RL) can stimulate plant defense against foliar diseases; however, its role in activation of systemic defense against root diseases remains unclear. Here, the effect of RL on root knot nematode Meloidogyne incognita (RKN) infestation was investigated in watermelon plants (Citrullus lanatus L.). Plants were exposed to 200 μmol m-2 s-1 photosynthetic photon flux density RL at the canopy level for 21 days using light-emitting photodiodes. The results showed that RL significantly suppressed gall formation and nematode development, which was closely associated with the RL-induced attenuation of oxidative stress in roots. Gene expression analysis showed that RL caused a transient upregulation of PR1 and WRKY70 transcripts at 7 days post inoculation in RKN-infected plants. Further investigation revealed that RL-induced systemic defense against RKN was attributed to increased jasmonic acid (JA) and salicylic acid (SA) content, and transcript levels of their biosynthetic genes in roots. Interestingly, while malondialdehyde content decreased, H2O2 accumulation increased in RL-treated RKN-plants, indicating a potential signaling role of H2O2 in mediating RL-induced systemic defense. Furthermore, analysis of enzymatic and non-enzymatic antidoxidants revealed that RL-induced enhanced defense agaist RKN was also attributed to increased activities of antioxidant enzymes as well as redox homeostasis. Taken together, these findings suggest that RL could enhance systemic resistance against RKN, which is mediated by a coordinated regulation of JA- and SA-dependent signaling, antioxidants, and redox homeostasis in watermelon plants.
Highlights
The root-knot nematode Meloidogyne incognita is a soil-dwelling, microscopic nematode that feeds exclusively on the cytoplasm of living plant cells
The results showed that control plants had 121 galls/plant root fresh weight, in sharp contrast, Red light (RL) decreased the whole gall number per plants by 19% compared with the control (Figure 1A)
Combined treatment of RL and root knot nematodes (RKN) resulted in a drastic upregulation in the transcript levels of those genes, which peaked at 7 dpi
Summary
The root-knot nematode Meloidogyne incognita is a soil-dwelling, microscopic nematode that feeds exclusively on the cytoplasm of living plant cells. JA pathway plays a pivotal role in systemic defense induction against root knot nematodes (RKN) in rice plants (Nahar et al, 2011). Exogenous SA added as a soil drench is able to restrict J2s of nematodes in tomato roots by triggering a systemic acquired resistance (SAR)-like response (Molinari et al, 2014). A recent study showed that Trichoderma could reduce parasitic nematodes by triggering host defense, which was attributed firstly to SAprimed defense that limited root invasion of nematodes, and secondly to enhanced JA-regulated defense that antagonized the nematodes-induced deregulation of JA-dependent immunity (Martìnez-Medina et al, 2017). BRs suppress tomato defense against root-knot nematodes, without involving the classical defense pathways, such as SA, JA/ET or ABA signaling, rather triggering the apoplastic RESPIRATORY BURST OXIDASE HOMOLOGdependent MPK1/2/3 activation in tomato plants (Song et al, 2017)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
