Transcriptome Analysis of Resistant and Susceptible Alfalfa Cultivars Infected With Root-Knot Nematode Meloidogyne incognita

Abstract

Nematodes are one of the major limiting factors in alfalfa production. Root-knot nematodes (RKN, Meloidogyne spp.) are widely distributed and economically important sedentary endoparasites of agricultural crops and they may inflict significant damage to alfalfa fields. As of today, no studies have been published on global gene expression profiling in alfalfa infected with RKN or any other plant parasitic nematode. Very little information is available about molecular mechanisms that contribute to pathogenesis and defense responses in alfalfa against these pests and specifically against RKN. In this work, we performed root transcriptome analysis of resistant (cv. Moapa 69) and susceptible (cv. Lahontan) alfalfa cultivars infected with RKN Meloidogyne incognita, widespread root-knot nematode species and a major pest worldwide. A total of 1,701,622,580 pair-end reads were generated on an Illumina Hi-Seq 2000 platform from the roots of both cultivars and assembled into 45,595 and 47,590 transcripts in cvs Moapa 69 and Lahontan, respectively. Bioinformatic analysis revealed a number of common and unique genes that were differentially expressed in susceptible and resistant lines as a result of nematode infection. Although the susceptible cultivar showed a more pronounced defense response to the infection, feeding sites were successfully established in its roots. Characteristically, basal gene expression levels under normal conditions differed between the two cultivars as well, which may confer advantage to one of the genotypes toward resistance to nematodes. Differentially expressed genes were subsequently assigned to known Gene Ontology categories to predict their functional roles and associated biological processes. Real-time PCR validated expression changes in genes arbitrarily selected for experimental confirmation. Candidate genes that contribute to protection against M. incognita in alfalfa were proposed and alfalfa-nematode interactions with respect to resistance are discussed.

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

“…The root-knot nematode (Meloidogyne spp.) comprises over 100 species, with Meloidogyne javanica, Meloidogyne arenaria, Meloidogyne hapla, and Meloidogyne incognita representing the most devastating threat to agricultural crop production [48]. The Meloidogyne spp.…”

“…Recently, RNASequencing has been frequently used in plant pathological studies to proile gene expression paterns in host plants and pathogens [93,94]. Diferential genetic expression proiles of many speciic genes involved in plant immune responses has been shown in resistant and susceptible plants challenged by root-knot nematodes [48,95]. The identiication of novel defenserelated transcripts and the elucidation of pathways involved in plant immune responses to nematodes have been recorded for important economic crops including coton [96], rice [97], and soybean [98].…”

Estudo da interação Musa acuminata-Meloidogyne incógnita

“…Neste estudo da interação Musa acuminata -Meloidogyne incognita foi usado o método RNAseq de Illumina para análise de transcritoma, o qual é considerado uma técnica eficiente que gera informação confiável do perfil de expressão gênica para construção de bibliotecas de RNAseq, e assim a detecção de transcritos pode ser realizada a partir de análises de bioinformática, permitindo identificar os genes diferencialmente expressos em genótipos contrastantes (Yazawa et al, 2013;Santini, 2014;Postnikova et al, 2015). As bibliotecas de expressão foram formadas quase que exclusivamente por transcritos originados de raízes de banana, Musa acuminata, o que foi verificado a partir das análises de mapeamento.…”

“…Outros trabalhos têm conseguido de forma similar o estudo de interação de Meloidogyne incognita com outros hospedeiros, como: cafeeiro, feijoeiro, alfafa entre outros, utilizando o mapeamento de transcritos em sequências expressas de referência para a identificação dos reads originados (Albuquerque, 2009;Santini, 2014;Postnikova et al, 2015).…”

“…No genótipo GN, os genes E22 e TL1 da família PR5 foram suprimidos aos 3 e 10 DAI, respectivamente, ao mesmo tempo em que observou-se o estabelecimento do nematoide, cômodo modo esperado para um genótipo suscetível. Esses genes são ativados principalmente em infecções por fungos, por bactérias e vírus (Van Loon et al, 2006;Liu et al, 2012;Postnikova et al, 2015) e também parecem ser importantes na defesa contra M.…”