Gene expression trade‐offs between defence and growth inEnglish elm induced byOphiostoma novo‐ulmi

Abstract

Wilt diseases caused by vascular pathogens include some of the most damaging stresses affecting trees. Dutch elm disease (DED), caused by the fungus Ophiostoma novo-ulmi, destroyed most of North American and European elm populations in the 20th century. The highly susceptible English elm, also known as Atinian clone, suffered the highest mortality rates during the last pandemic event, probably due to its lack of genetic diversity. To study the DED pathosystem, we inoculated English elm ramets with O. novo-ulmi and evaluated xylem anatomy, molecular response, and disease symptoms. The high DED susceptibility of the clone was linked to xylem structure. The transcript levels changed significantly for 1,696 genes during O. novo-ulmi invasion.Genes covering different steps of the plant immune system were identified, many of which showed homology with Arabidopsis thaliana genes involved in systemic acquired resistance.Induction of several pathogenesis-related proteins and repression of fasciclin-like arabinogalactan proteins and other cell wall biosynthesis pathways evidence unbalanced costs between growth and defence mechanisms far from the inoculation point. This study sheds light on elm molecular defence mechanisms against DED. KEYWORDSDutch elm disease, microarrays, plant immune system, systemic acquired resistance, Ulmus minor, vascular pathogen | INTRODUCTIONTrees are exposed to many instances of environmental interaction and stress throughout their life cycle. These include pests and diseases that can cause dramatic mortality events in forests and loss of foundation species and iconic trees (e.g., Ellison et al., 2005). Diseases affecting tree vascular systems are usually very harmful due to the crucial role of these tissues in transporting water, nutrients, hormones, and other compounds. Dutch elm disease (DED) is a vascular wilt disease caused by the pathogenic fungi Ophiostoma ulmi planted in a research plot at Puerta de Hierro Forest Breeding Centre (Madrid, Spain; 40.456238 N, 3.751823 W) These observations were performed at sampling times (1, 3, 7, 14, and 21 dpi) and at 28, 60, and 120 dpi. | Characterization of anatomical structureAnatomical parameters were measured in two control ramets. Two additional ramets inoculated with the pathogen were sampled to visualize xylem responses to infection by O. novo-ulmi.

Fasciclin-like arabinogalactan gene family in Nicotiana benthamiana: genome-wide identification, classification and expression in response to pathogens

“…AtFLA1/2/8 were decreased by pathogen challenge, oxidative stress and in ascorbate-deficient vtc mutants [44]. The fungus Ophiostoma novo-ulmi reduced the expression of FLAs in English elm ramets [45]. Our results…”

Fasciclin-like arabinogalactan gene family in Nicotiana benthamiana: genome-wide identification, classification and expression in response to pathogens

“…AtFLA1/2/8 were decreased by pathogen challenge, oxidative stress and in ascorbate-de cient vtc mutants [49]. The fungus Ophiostoma novo-ulmi reduced the expression of FLAs in English elm ramets [50]. Our results show that almost all NbFLAs were speci cally downregulated by TuMV and Pst DC3000 infection and this suggests that NbFLAs may have speci c roles in pathogen infection.…”

Breeding and scientific advances in the fight against Dutch elm disease: Will they allow the use of elms in forest restoration?

“…Unlike Perdiguero et al (2018), these authors reported several JA-related genes overexpressed with the presence of O. novo-ulmi. However, the changes occurred at the inoculation point, indicating that local defense responses may be regulating differently from the responses in distal parts observed by Perdiguero et al (2018). Brand new methodologies such as RNAseq could be accurate and promising tools to achieve the goal of fully understanding the molecular aspects of elm-Ophiostoma interactions.…”

“…Recent works have advanced in this direction: U. americana trees were inoculated with O. novo-ulmi and the expression of various defense-related genes was analyzed by RT-qPCR at different hours post-inoculation in samples collected near the inoculation point (Sherif et al 2016(Sherif et al , 2017. Unlike Perdiguero et al (2018), these authors reported several JA-related genes overexpressed with the presence of O. novo-ulmi. However, the changes occurred at the inoculation point, indicating that local defense responses may be regulating differently from the responses in distal parts observed by Perdiguero et al (2018).…”

“…Using the data from this transcriptome, a microarray experiment was designed and performed (Perdiguero et al 2018). Atinian elms were inoculated in the trunk base with O. novo-ulmi and branch samples distal from the inoculation point were collected at different days post inoculation.…”