Resistant and Susceptible Responses in Tomato to Cyst Nematode are Differentially Regulated by Salicylic Acid

Abstract

To understand the machinery underlying a tomato cultivar harboring the Hero A gene against cyst nematode using microarrays, we first analyzed tomato gene expression in response to potato cyst nematode (PCN; Globodera rostochiensis) during the early incompatible and compatible interactions at 3 and 7 days post-inoculation (dpi). Transcript levels of the phenylalanine ammonia lyase (PAL) and Myb-related genes were up-regulated at 3 dpi in the incompatible interaction. Transcription of the genes encoding pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) was also up-regulated at 3 dpi in the incompatible interaction. On the other hand, the four genes (PAL, Myb, PDC and ADH) were down-regulated in the compatible interaction at 3 dpi. When the expression levels of several pathogenesis-related (PR) protein genes in tomato roots were compared between the incompatible and compatible interactions, the salicylic acid (SA)-dependent PR genes were found to be induced in the incompatible interaction at 3 dpi. The PR-1(P4) transcript increased to an exceptionally high level at 3 dpi in the cyst nematode-infected resistant plants compared with the uninoculated controls. The free SA levels were elevated to similar levels in both incompatible and compatible interactions. We then confirmed that PR-1(P4) was not significantly induced in the NahG tomato harboring the Hero A gene, compared with the resistant cultivar. We thus found that PR-1(P4) was a hallmark for the cultivar resistance conferred by Hero A against PCN and that nematode parasitism resulted in the inhibition of the SA signaling pathway in the susceptible cultivars.

The Impact of Plant-Parasitic Nematodes on Agriculture and Methods of Control

“…During nematode infections, PR transcripts may accumulate in high concentrations and are associated with the long distance immune response termed systemic acquired resistance (SAR) [109]. Increased expression of PR-1(P4) transcripts was observed at 3 days' post-infection in the G. rostochiensis-infected resistant plants compared with the uninoculated controls [110].…”

Role of phytohormones (indol acetic acid, jasmonic acid, salcylic acid, and ethylene) in nematode-plant interactions

“…(Wubben et al, 2008) reported that A. thaliana mutants deficient in SA were more susceptible than the wild types to cyst nematode. SA also plays a significant role in the reduction of parasitism between cyst nematode and plant (Wubben et al, 2008); can be increased by the presence of protease inhibitors, senescence associated and seed specific proteins associated with JA (Uehara et al, 2010). Ethyleneinduced genes activated by ripping and allow compatible interaction between plants and PPNs (Uehara et al, 2010).…”

“…SA also plays a significant role in the reduction of parasitism between cyst nematode and plant (Wubben et al, 2008); can be increased by the presence of protease inhibitors, senescence associated and seed specific proteins associated with JA (Uehara et al, 2010). Ethyleneinduced genes activated by ripping and allow compatible interaction between plants and PPNs (Uehara et al, 2010). Susceptibility of plants to cyst nematodes can also be facilitated by ET signaling transduction (Uehara et al, 2010;Wubben et al, 2008).…”

“…Ethyleneinduced genes activated by ripping and allow compatible interaction between plants and PPNs (Uehara et al, 2010). Susceptibility of plants to cyst nematodes can also be facilitated by ET signaling transduction (Uehara et al, 2010;Wubben et al, 2008). Plant hormones like ET and JA have the ability to interfere with tomato SA-inducible PCN resistance pathway in susceptible cultivars.…”

“…Plant hormones like ET and JA have the ability to interfere with tomato SA-inducible PCN resistance pathway in susceptible cultivars. In addition, auxin response factor induces the compatible interaction between plant and PCN (Uehara et al, 2010). Thus, phytohormones involved in many processes of plant nematode parasitism like the involvement of invasion plant cell and induction of syncytium.…”