Integrated signaling networks in plant responses to sedentary endoparasitic nematodes: a perspective

Abstract

Sedentary plant endoparasitic nematodes can cause detrimental yield losses in crop plants making the study of detailed cellular, molecular, and whole plant responses to them a subject of importance. In response to invading nematodes and nematode-secreted effectors, plant susceptibility/resistance is mainly determined by the coordination of different signaling pathways including specific plant resistance genes or proteins, plant hormone synthesis and signaling pathways, as well as reactive oxygen signals that are generated in response to nematode attack. Crosstalk between various nematode resistance-related elements can be seen as an integrated signaling network regulated by transcription factors and small RNAs at the transcriptional, posttranscriptional, and/or translational levels. Ultimately, the outcome of this highly controlled signaling network determines the host plant susceptibility/resistance to nematodes.

Plant-Mediated Systemic Interactions Between Pathogens, Parasitic Nematodes, and Herbivores Above- and Belowground

“…tomato, have an effector repertoire that enables them to interact with all known major signaling pathways to activate the SA signaling pathway by sabotaging its activators and stimulating its repressor (171). In addition, some root-feeding nematodes secrete chorismate mutase (CM) involved in SA biosynthesis and manipulate lipid signaling involved in JA-induced defense (47,93). Consequently, local manipulation of defense hormone signaling pathways by phytophages may attenuate systemic induced defense responses to other plant feeding organisms, either within or across compartments.…”

“…Root feeding by sedentary endoparasitic nematodes results in the production and accumulation of SA, JA, and ET at the site of infection (67). Subsequently, transcriptional reprogramming results in the activation of the core defense system involving SA/JA/ET-mediated pathways (80,93,168). For example, in A. thaliana, cyst nematode-induced JA-mediated defense depends on the protein phosphatase AP2C1, which is a negative regulator of the mitogen-activated protein kinases MPK3 and MPK6, two positive regulators of plant defense responses controlling ET and JA biosynthesis (140).…”

Ethylene response pathway modulates attractiveness of plant roots to soybean cyst nematode Heterodera glycines

“…Transcriptome and microarray analyses of host roots infected with plant nematodes showed differential changes in the expression of genes responding to several hormones including auxin, ethylene (ET), jasmonic acid (JA), salicylic acid (SA), brassinosteroids (BR), gibberellins (GA), and abscisic acid (ABA)222324. A number of studies have indicated that the signaling pathways of SA, JA, BR, ABA, and ET are involved in the defense response of host plants to nematodes252627282930. Auxin, ET and GA have also been reported to play a positive role in the early stages of development of nematode feeding cells313233.…”

Plant elicitor peptides promote plant defences against nematodes in soybean

“…Rapid production of ROS in the apoplast by RBOHD is an early defence response that occurs after the successful recognition of pathogens by the plant immune system, and that can kill pathogens, trigger hypersensitive cell death, activate the expression of defence‐related genes and interact with plant signalling networks to modulate local and systemic immunity (Apel and Hirt, ). Studies in several different plant species have also indicated that ROS play important roles in plant–nematode interactions (Li et al ., ). In certain compatible interactions, nematodes appear to utilize effector molecules to manipulate ROS levels and to suppress effective defence responses in the host plant (Dubreuil et al ., ; Lin et al ., ; Siddique et al ., ), whereas, in other interactions, ROS activation contributes to basal defences or is associated with incompatibility (Kandoth et al ., ; Kong et al ., ; Melillo et al ., ; Teixeira et al ., ).…”