Differentially expressed small RNAs in Arabidopsis galls formed by Meloidogyne javanica: a functional role for miR390 and its TAS3‐derived tasiRNAs

Abstract

SummaryRoot-knot nematodes (RKNs) induce inside the vascular cylinder the giant cells (GCs) embedded in the galls. The distinctive gene repression in early-developing GCs could be facilitated by small RNAs (sRNA) such as miRNAs, and/or epigenetic mechanisms mediated by 24nt-sRNAs, rasiRNAs and 21-22nt-sRNAs. Therefore, the sRNA-population together with the role of the miR390/TAS3/ARFs module were studied during early gall/GC formation.Three sRNA libraries from 3-d-post-inoculation (dpi) galls induced by Meloidogyne javanica in Arabidopsis and three from uninfected root segments were sequenced following Illumina-Solexa technology. pMIR390a::GUS and pTAS3::GUS lines were assayed for nematode-dependent promoter activation. A sensor line indicative of TAS3-derived tasiRNAs binding to the ARF3 sequence (pARF3:ARF3-GUS) together with a tasiRNA-resistant ARF3 line (pARF3:ARF3m-GUS) were used for functional analysis.The sRNA population showed significant differences between galls and controls, with high validation rate and correspondence with their target expression: 21-nt sRNAs corresponding mainly to miRNAs were downregulated, whilst 24-nt-sRNAs from the rasiRNA family were mostly upregulated in galls. The promoters of MIR390a and TAS3, active in galls, and the pARF3:ARF3-GUS line, indicated a role of TAS3-derived-tasiRNAs in galls.The regulatory module miR390/TAS3 is necessary for proper gall formation possibly through auxin-responsive factors, and the abundance of 24-nt sRNAs (mostly rasiRNAs) constitutes a gall hallmark.

The MicroRNA390/TAS3 Pathway Mediates Symbiotic Nodulation and Lateral Root Growth

“…More recently, the miR390/TAS3 pathway has been implicated in the interaction of Arabidopsis plants with the parasitic root-knot nematodes. The use of tasiARF sensor and tasiARF-resistant ARF3 lines revealed that this regulatory module is required for nematode-induced gall formation in Arabidopsis roots (Cabrera et al, 2016). In addition, the miR390/TAS3 pathway has been linked to root nodule symbiosis in L. japonicus.…”

Genome-wide identification and characterization of miRNAome from tomato (Solanum lycopersicum) roots and root-knot nematode (Meloidogyne incognita) during susceptible interaction

“…In recent years, the role of plant miRNAs in regulation of genes involved in plant-nematode interaction have also been reported [8,16,17]. The most abundant targets of miRNAs that have been reported with modulated expression during nematode infection are transcription factors.…”

“…Further, Zhao and coworkers [20] reported that miR319/TCP4 module acts as a regulator of jasmonic acid levels upon RKN infection in tomato and thereby, affects the nature of host resistance. Recently, functional role of miR390/TAS3 in regulating ARF s at early gall development was studied during Arabidopsis- RKN interaction [17]. In animals, role of miRNAs in relation to diseases have been suggested by predicting the miRNA targets computationally in humans, insects and metazoans [21–23].…”

Long-Term In Vitro System for Maintenance and Amplification of Root-Knot Nematodes in Cucumis sativus Roots

“…Moreover, J2s from these cultures can be used directly after a simple hatching step in aseptic conditions to infect plants for experiments with different in vitro grown plant species. Successful experiments have been performed with this procedure on different genotypes of Arabidopsis , tobacco, and tomato (Barcala et al, 2010; Escobar et al, 2010; Portillo et al, 2013; Cabrera et al, 2014, 2015, 2016). …”