Systemic responses in a tolerant olive (Olea europaea L.) cultivar upon root colonization by the vascular pathogen Verticillium dahliae

Abstract

Verticillium wilt of olive (VWO) is caused by the vascular pathogen Verticillium dahliae. One of the best VWO management measures is the use of tolerant cultivars; however, our knowledge on VWO tolerance/resistance genetics is very limited. A transcriptomic analysis was conducted to (i) identify systemic defense responses induced/repressed in aerial tissues of the tolerant cultivar Frantoio upon root colonization by V. dahliae, and (ii) determine the expression pattern of selected defense genes in olive cultivars showing differential susceptibility to VWO. Two suppression subtractive hybridization cDNA libraries, enriched in up-regulated (FU) and down-regulated (FD) genes respectively, were generated from “Frantoio” aerial tissues. Results showed that broad systemic transcriptomic changes are taking place during V. dahliae-“Frantoio” interaction. A total of 585 FU and 381 FD unigenes were identified, many of them involved in defense response to (a)biotic stresses. Selected genes were then used to validate libraries and evaluate their temporal expression pattern in “Frantoio.” Four defense genes were analyzed in cultivars Changlot Real (tolerant) and Picual (susceptible). An association between GRAS1 and DRR2 gene expression patterns and susceptibility to VWO was observed, suggesting that these transcripts could be further evaluated as markers of the tolerance level of olive cultivars to V. dahliae.

Transcriptomic Analysis of Olea europaea L. Roots during the Verticillium dahliae Early Infection Process

“…In addition, a very strong overexpression of a subcluster C, chitinase class I (PR4) was noted, this probably being a frontline defense protein against the fungus. In recent work, Gómez-Lama Cabanás et al (2015) studied a subtractive cDNA library of a different olive cultivar that is far more tolerant to the pathogen and different tissues than the one in this work. So it is not surprising that there are differences between the results of the two studies; however, a few of the genes described as induced in response to the pathogen infection are the same or related.…”

“…Recently, host resistance has been tested using a large number of olive genotypes (Arias‐Calderón et al, 2015a, 2015b; Trapero et al, 2015). Other aspects of the infection have been investigated, including the response to stem‐puncture inoculation (López‐Escudero et al, 2007), the colonization process (Prieto et al, 2009), natural recovery as a control strategy (Bubici and Cirulli, 2014), the effect of soil temperature in olive response to VWO (Calderón et al, 2014), systemic responses of olive potentially related to VWO resistance (Gómez‐Lama Cabanás et al, 2015), and V. dahliae genetic structure and cell‐wall‐degrading enzymes as pathogenicity factors (Gharbi et al, 2015a, 2015b).…”

Tolerance of olive (Olea europaea) cv Frantoio to Verticillium dahliae relies on both basal and pathogen‐induced differential transcriptomic responses

“…The term tolerance (Robb, ) is used here for olive varieties able to cope with infections of V. dahliae without developing severe symptoms of the disease. ‘Frantoio’ is thus considered as one of the most tolerant cultivars to VWO, in contrast to, for example, the very susceptible cv Picual (López‐Escudero et al ., ; Martos‐Moreno et al ., ; Trapero et al ., , ; Gómez‐Lama Cabanás et al ., ).…”

“…Moreover, whether differential genetic responses could be related to the VWO susceptibility/tolerance level of olive cultivars has seldom been investigated. Recently, transcriptomic changes occurring in above‐ground tissues during the interaction of V. dahliae (D pathotype) with ‘Frantoio’ roots were reported, many of them related to defence responses against a/biotic stresses (Gómez‐Lama Cabanás et al ., )…”

Review: Omics and Strategic Yield Improvement in Oil Crops

“…In olive, transcripts that were induced during root colonization by Verticillium dahlia were identified using subtractive suppressive hybridization [205]. The results showed that many of these genes have functions in defense responses towards both biotic and abiotic stresses.…”