Comprehensive Transcriptome Profiling in Tomato Reveals a Role for Glycosyltransferase in Mi-Mediated Nematode Resistance

Abstract

Root-knot nematode (RKN; Meloidogyne spp.) is a major crop pathogen worldwide. Effective resistance exists for a few plant species, including that conditioned by Mi in tomato (Solanum lycopersicum). We interrogated the root transcriptome of the resistant (Mi1) and susceptible (Mi-) cultivars 'Motelle' and 'Moneymaker,' respectively, during a time-course infection by the Mi-susceptible RKN species Meloidogyne incognita and the Mi-resistant species Meloidogyne hapla. In the absence of RKN infection, only a single significantly regulated gene, encoding a glycosyltransferase, was detected. However, RKN infection influenced the expression of broad suites of genes; more than half of the probes on the array identified differential gene regulation between infected and uninfected root tissue at some stage of RKN infection. We discovered 217 genes regulated during the time of RKN infection corresponding to establishment of feeding sites, and 58 genes that exhibited differential regulation in resistant roots compared to uninfected roots, including the glycosyltransferase. Using virus-induced gene silencing to silence the expression of this gene restored susceptibility to M. incognita in 'Motelle,' indicating that this gene is necessary for resistance to RKN. Collectively, our data provide a picture of global gene expression changes in roots during compatible and incompatible associations with RKN, and point to candidates for further investigation.

How Durable is Root Knot Nematode Resistance in Tomato?

“…Jaubert et al (2005) reported a molecule Mi-CRT, localized at the tip of the nematode stylet, and at the cell wall of the GCs, supporting oesophageal molecule insertion during the establishment of NFS. Similar studies identified different candidate molecules from oesophageal gland of M. incognita (Huang et al 2005;Mitreva-Dautova et al 2006;Schaff et al 2007). Authors speculated that those molecules could be acting as a facilitator of entering and intercellular movement of the RKN at the early phases of the parasitism.…”

“…Those resistance genes are commercially used in tomato breeding programs in controlling three main RKN species, M. (Schaff et al 2007). On the other hand, callose or lignin synthesis at plant cell wall acts as a physical barrier of stylet penetration in where glycosyltransferases genes may play a role in cell wall synthesis reported by Egelund et al (2004).…”

“…However, few study has been carried out to date on induced resistance to plant parasitic nematodes, whereas most of the existing reports are referred to induced resistance against RKN in tomato (Cooper et al 2005;Javed et al 2007). In addition, virus inducing gene silencing (VIGS) study showed that a glycosyltransferase gene can enhance Mi-1 mediated resistance to RKN in tomato (Schaff et al 2007). Bhattarai et al (2007) also reported that nematodes couldn't capable to persist and to eat on tissues without regulating cytosolic heat shock protein Hsp90 expression, indicating Hsp90 is a required element as a molecular tool to act together Rar1 and Sgt1 in certain R gene reactions.…”

“…Transcriptomic analysis is also employed to identify the differentially expressed genes during nematode infection. Schaff et al (2007) conducted a transcriptome analysis study including a resistance (cultivar Motelle homozygous for Mi-1) and a susceptible (Money-maker) tomato cultivar in where candidate gene glycosyltransferase was detected which was up-regulated six fold during invasion of M. incognita, but silencing of the candidate gene using VIGS technique abolished Mi-1-mediated resistance in the cultivar Motelle. Numerous resistance genes were identified by different studies those are silenced into plant cells using RNAi strategy.…”

Transcriptomic Analysis of Nematode Infestation

“…Improvements in spotting technology now routinely allow up to 30,000 cDNA fragments to be spotted on a single chip. These cDNA chips are routinely created in research labs and used for specific studies (Alkharouf et al 2006 ;Khan et al 2004 ;Schaff et al 2007) . However, the use of cDNA microarrays has been somewhat problematic due to potential errors caused by cross-hybridization and/or nonuniformity of hybridization as the result of the presence of palindromes or homopolymeric runs.…”