The microRNA response associated with methyl jasmonate-induced resistance in Norway spruce bark

Epigenetics: a catalyst of plant immunity against pathogens

“…For example, gene bodies of NLRs in common bean (Phaseolus vulgaris) are targeted by RdDM, of which approximately half are methylated in all three contexts (CG, CHH, CHG) (Richard et al, 2018b), while other plant species lack gene body methylation altogether (Bewick et al, 2016). Furthermore, conifers differ from flowering plants in that 21-nt sRNAs, rather than 24-nt sRNAs, make up the majority of the sRNA population in vegetative tissues, despite their huge TE-rich genomes (Nakamura et al, 2019;Wilkinson et al, 2021). Perhaps most importantly, TEs make up only c. 20% of the genome in Arabidopsis, compared to > 80% in maize and wheat (Quesneville, 2020), which makes these crops more sensitive to the introduction of epigenetic variation (Li et al, 2014).…”

Small RNAs >26 nt in length associate with AGO1 and are upregulated by nutrient deprivation in the alga Chlamydomonas

“…Green algal species: C. reinhardtii ( Valli et al 2016 ) and V. carteri ( Li et al 2014 ). Land plant species: P. patens ( Xia et al 2016 ), M. polymorpha ( Lin et al 2016 ), P. abies ( Wilkinson et al 2021 ), G. biloba ( Zhang et al 2015 ), Z. mays ( Liu et al 2014 ), and A. thaliana ( Schalk et al 2017 ).…”

Transcriptomic changes during the establishment of long‐term methyl jasmonate‐induced resistance in Norway spruce

“…However, it is has been reported in Arabidopsis that 21/22 nt sRNAs can also guide DNA methylation via a noncanonical RdDM pathway which involves AGO6 (Cuerda‐Gil & Slotkin, 2016). Interestingly, the expression of 24 nt sRNAs is very low in Norway spruce vegetative tissues whereas 21/22 nt sRNAs are common (Nystedt et al, 2013; Wilkinson et al, 2021). We may thus speculate that noncanonical RdDM pathway with 21/22 nt guide sRNAs is the canonical pathway in vegetative Norway spruce tissues (Wilkinson et al, 2021).…”

“…Interestingly, the expression of 24 nt sRNAs is very low in Norway spruce vegetative tissues whereas 21/22 nt sRNAs are common (Nystedt et al, 2013; Wilkinson et al, 2021). We may thus speculate that noncanonical RdDM pathway with 21/22 nt guide sRNAs is the canonical pathway in vegetative Norway spruce tissues (Wilkinson et al, 2021). In addition to RdDM genes, we also found that MeJA treatment repressed genes encoding for DNA glycosylases, enzymes which catalyse the first step in active in removal of DNA methylation (Zhang et al, 2018), further supporting our hypothesis that MeJA treatment triggers a loss of DNA methylation in Norway spruce.…”