Comparing systemic defence‐related gene expression changes upon migratory and sedentary nematode attack in rice

Abstract

Complex defence signalling pathways, controlled by different hormones, are known to be involved in the reaction of plants to a wide range of biotic and abiotic stress factors. Here, we studied the differential expression of genes involved in stress and defence responses in systemic tissue of rice infected with the root knot nematode (RKN) Meloidogyne graminicola and the migratory root rot nematode Hirschmanniella oryzae, two agronomically important rice pathogens with very different lifestyles. qRT-PCR revealed that all investigated systemic tissues had significantly lower expression of isochorismate synthase, a key enzyme for salicylic acid production involved in basal defence and systemic acquired resistance. The systemic defence response upon migratory nematode infection was remarkably similar to fungal rice blast infection. Almost all investigated defence-related genes were up-regulated in rice shoots 3 days after root rot nematode attack, including the phenylpropanoid pathway, ethylene pathway and PR genes, but many of which were suppressed at 7 dpi. Systemic shoot tissue of RKN-infected plants showed similar attenuation of expression of almost all studied genes already at 3 dpi, with clear attenuation of the ethylene pathway and methyl jasmonate biosynthesis. These results provide an interesting starting point for further studies to elucidate how nematodes are able to suppress systemic plant defence mechanisms and the effect in multitrophic interactions.

Not to be suppressed? Rethinking the host response at a root-parasite interface

“…Most of the defense marker genes examined had increased systemic expression in the root tissues that was opposite to the consistent repression observed in the aerial tissues of the same plants [29,37].…”

“…Defense marker genes were down-regulated in aerial tissues of tomato and rice plants compared to that in non-infected plants, suggesting that the nematode infestation had induced a systemic suppression of defense signaling throughout the plant [29,37]. Based on these observations, a systemic suppression of host defense signaling in roots could also therefore be expected.…”

Differences in Hormonal Signaling Triggered by Two Root-Feeding Nematode Species Result in Contrasting Effects on Aphid Population Growth

“…In rice, M. graminicola infestation suppresses both SA and JA pathways in the leaves starting from 3 d.a.i. onwards (Kyndt et al, 2012b). Similarly, several SA and JA marker genes are suppressed in the leaves of A. thaliana infested for 5-14 days with M. incognita (Hamamouch et al, 2011).…”

Rice Root-Knot Nematode (Meloidogyne graminicola) an Emerging Problem

“…undertook phylogenetic analysis based on the sequences of partial internal transcribed spacer (ITS) of the rRNA genes and indicated that all Nepalese isolates formed a distinct clade within known isolates of M. graminicola. The former study provides RNA-seq data obtained from roots infected with root rot nematode H.oryzae in comparison with uninfected roots and root galls induced by M. graminicola, at three and seven days after inoculation compared with control root tips (Kyndt et al, 2012). Ji et al, (2013) focus on the gene expression inside laser capture microdisected giant cells at 7 and 14 DAI and compared this profile with vascular cells from uninfected roots.…”

“…Ji et al, (2013) focus on the gene expression inside laser capture microdisected giant cells at 7 and 14 DAI and compared this profile with vascular cells from uninfected roots. In rice, M. graminicola able to suppress transcription of key immune regulatory genes (Kyndt et al, 2012). M. graminicolaeffector proteins expressed in oesophageal gland cells are currently being analysed for their role in RKN-rice interaction (Nguyen, 2014) (Plate.…”