Effect of Methyl Jasmonate in Gene Expression, and in Hormonal and Phenolic Profiles of Holm Oak Embryogenic Lines Before and After Infection With Phytophthora cinnamomi

Abstract

The dieback syndrome affecting Quercus ilex and other oak species impels the search for tolerant plant genotypes, as well as methods of plant immunization against such infections. Elicitation treatments can be an effective strategy to activate plant defense response and embryogenic lines represent a promising tool to generate new tolerant genotypes and also to study early markers involved in defense response. The aim of the presented work was to investigate changes in gene expression, and in hormonal and phenolic profiles induced in three holm oak embryogenic lines (ELs) elicited with methyl jasmonate (MeJA) before and after infection with the oomycete Phytophthora cinnamomi, which is the main biotic agent involved in this pathogenic process. The three ELs, derived from three genotypes, showed different basal profiles in all tested parameters, noting that the VA5 naïve genotype from a scape tree was characterized by a basal higher expression in NADPH-dependent cinnamyl alcohol dehydrogenase (CAD) and chalcone synthase (CHS) genes and also by higher caffeic acid content. Our work also identifies changes triggered by MeJA elicitation in holm oak embryogenic lines, such as increases in ABA and JA contents, as well as in levels of most of the determined phenolic compounds, especially in caffeic acid in Q8 and E00 ELs, but not in their biosynthesis genes. Irrespective of the EL, the response to oomycete infection in holm oak elicited plant material was characterized by a further increase in JA. Since JA and phenols have been described as a part of the Q. ilex defense response against P. cinnamomi, we propose that MeJA may act as an induced resistance (IR) stimulus and that in our embryogenic material induced both direct (detected prior to any challenge) and primed (detected after subsequent challenge) defense responses.

Tolerant Epitypes of Elicited Holm Oak Somatic Embryos Could Be Revealed by Challenges in Dual Culture with Phytophthora cinnamomi Rands

“…When the tissues of selected lines inhibit the growth of a mycelium, the explanation may lie in their production of externally exported resistance compounds. Dual culture assays have confirmed the chemotactic attraction of P. cinnamomi mycelia toward holm oak somatic embryos to be dependent on the latter's genotype [15,16]. The same has also been observed in vitro with shoots and leaves [13] and in roots during the infection process in vivo [39].…”

“…The genetic transformation of somatic embryos using a Gnk2-like protein may also allow genotypes with improved anti-oomycete activity to be obtained [14]. The induction of epigenetic changes on somatic embryos elicits a defense response and provides another opportunity to obtain tolerant holm oak trees [15,16]. There is increasing evidence that following exposure to an environmental stimulus, different genotypes acquire some kind of epigenetic memory that determines new behavior when restimulated.…”

Response of Biofortified Green Bean Plants to Colletotrichum lindemuthianum

“…Notably, various previous studies have consistently reported elevated levels of phenolic compounds within symptomatic spots caused by various pathogens, such as Colletotrichum spp. [16], Pyrenophora tritici-repentis race 1 [32], Gloeosporium spp., Penicillium expansum, Monilinia fructigena [33], Glomerella cingulata [34], and Phytophthora cinnamomi [35].…”

Advances in Quercus ilex L. breeding: the CRISPR/Cas9 technology via ribonucleoproteins

“…Among these stressors, Phytophthora cinnamomi Rands is considered the main pathogen responsible for the oak decline. In addition, the effects of climate change, with increasing periods of drought, aggravate the pathology caused by P. cinnamomi , and survival of this agroforestry system is becoming a challenge ( Morcillo et al., 2022 ).…”