Plant-mediated RNA interference of effector gene Mc16D10L confers resistance against Meloidogyne chitwoodi in diverse genetic backgrounds of potato and reduces pathogenicity of nematode offspring

Abstract

Meloidogyne chitwoodi is a major problem for potato production in the Pacific Northwest of the USA. In spite of long term breeding efforts no commercial potato cultivars with resistance to M. chitwoodi exist to date. The RMcUblb) resistance gene against M. chitwoodi has been introgressed from Solanum bulbocastanum into cultivated potato (S. tuberosum), but M. chitwoodi pathotypes are able to overcome this resistance. In this study, an RNA interference (RNAi) transgene targeting the M. chitwoodi effector gene Mcl6D10L was introduced into potato cvs Russet Burbank and Desiree, and the advanced breeding line PA99N82-4, which carries the RMcl(blb) gene. Stable transgenic lines were generated for glasshouse infection assays. At 35 days after inoculation (DAI) with M. chitwoodi race 1 the number of egg masses (g root)-1 formed on RNAi lines of cvs Russet Burbank and Desiree was reduced significantly by up to 68% compared to empty vector control plants. At 55 DAI, the number of eggs was reduced significantly by up to 65%. In addition, RNAi of Mcl6D10L significantly reduced the development of egg masses and eggs formed by the RMcl(blb) resistance breaking M. chitwoodi pathotype Roza on PA99N82-4 by up to 47 and 44%, respectively. Importantly, the plant-mediated silencing effect of Mcl6D10L was transmitted to M. chitwoodi offspring and significantly reduced pathogenicity in the absence of selection pressure on empty vector control plants. This finding suggests that the RNAi effect is stable and nematode infection decreases regardless of the genotype of the host once the RNAi process has been initiated in the nematode through a transgenic plant. In summary, plantmediated down-regulation of effector gene Mcl6D10L provides a promising new tool for molecular breeding against M. chitwoodi.

The status of RNAi-based transgenic research in plant nematology

“…Additionally, the 16D10i-2 RNAi transgene did not interfere with the natural resistance conferred by the R Mc1(blb) gene, which has been introgressed into PA99N82–4. As RNAi-induced resistance against M. chitwoodi reached comparable levels in all cultivars tested, genotype specific factors are unlikely to limit the use of RNAi in a broad range of germplasm (Dinh et al, 2014a ). Furthermore, stable transgenic lines of A. thaliana and potato expressing dsRNA of Mc16D10L , have also been reported to confer resistance to M. chitwoodi (Dinh et al, 2014b ).…”

“…Furthermore, stable transgenic lines of A. thaliana and potato expressing dsRNA of Mc16D10L , have also been reported to confer resistance to M. chitwoodi (Dinh et al, 2014b ). Nematodes feeding on these transgenics also appeared to transmit the downregulation of the targeted gene to their offspring and this effect was maintained over several generations (Dinh et al, 2014a , b ). Therefore, as seen in C. elegans (Grishok et al, 2000 ), plant-mediated RNAi effects could become systemic and heritable in PPNs.…”

RNAi-induced silencing of an effector confers transcriptional oscillation in another group of effectors in the root-knot nematode, Meloidogyne incognita

“…Further, functional characterisation of the pioneer genes was done by several researchers. The 16D10 peptide, also known as msp-16, was demonstrated to be necessary for infectivity and pathogenicity of RKN in Arabidopsis (Huang et al, 2006a), grapevines (Yang et al, 2013) and potato (Dinh et al, 2014) using RNA interference (RNAi) technology. In parallel, 16D10 was shown to interact with the SCARECROW-like transcription factor of Arabidopsis using yeast two-hybrid assays (Huang et al, 2006b).…”

Host-Induced Silencing of Two Pharyngeal Gland Genes Conferred Transcriptional Alteration of Cell Wall-Modifying Enzymes of Meloidogyne incognita vis-à-vis Perturbed Nematode Infectivity in Eggplant

“…Since J3 and J4s are considered to be the non-feeding stages (Jones et al, 2013), RNAi effect was transmitted across the different developmental stages of RKN and presumably offspring having defunct msp-18 / msp-20 gene was produced. The heritable nature of RNAi has previously been described in Caenorhabditis elegans (Grishok et al, 2000), M. javanica (Gleason et al, 2008), and M. chitwoodi (Dinh et al, 2014). …”

“…Using HIGS approach, multitude of effector genes have been functionally validated in detail in various host plants. Among the pioneer genes, msp-16 /peptide16D10 was shown to be crucial for RKN infectivity and pathogenicity in Arabidopsis (Huang et al, 2006), grapevines (Yang et al, 2013), and potato (Dinh et al, 2014). HIGS of msp-9 gene had impaired the infection ability of M. incognita in Arabidopsis (Xue et al, 2013).…”