Downregulation of a barley (Hordeum vulgare) leucine-rich repeat, non-arginine-aspartate receptor-like protein kinase reduces expression of numerous genes involved in plant pathogen defense

Abstract

Pattern recognition receptors represent a first line of plant defense against pathogens. Comparing the flag leaf transcriptomes of barley (Hordeum vulgare L.) near-isogenic lines varying in the allelic state of a locus controlling senescence, we have previously identified a leucine-rich repeat receptor-like protein kinase gene (LRR-RLK; GenBank accession: AK249842), which was strongly upregulated in leaves of early-as compared to late-senescing germplasm. Bioinformatic analysis indicated that this gene codes for a subfamily XII, non-arginine-aspartate (non-RD) LRR-RLK. Virus-induced gene silencing resulted in a two-fold reduction of transcript levels as compared to controls. Transcriptomic comparison of leaves from untreated plants, from plants treated with virus only without any plant sequences (referred to as 'empty virus' control), and from plants in which AK249842 expression was knocked down identified numerous genes involved in pathogen defense. These genes were strongly induced in 'empty virus' as compared to untreated controls, but their expression was significantly reduced (again compared to 'empty virus' controls) when AK249842 was knocked down, indicating that their expression partially depends on the LRR-RLK investigated here. Expression analysis, using datasets from BarleyBase/PLEXdb, demonstrated that AK249842 transcript levels are heavily influenced by the allelic state of the well-characterized mildew resistance a (Mla) locus, and that the gene is induced after powdery mildew and stem rust infection. Together, our data suggest that AK249842 is a barley pattern recognition receptor with a tentative role in defense against fungal pathogens, setting the stage for its full functional characterization.

CaLRR-RLK1, a novel RD receptor-like kinase from Capsicum annuum and transcriptionally activated by CaHDZ27, act as positive regulator in Ralstonia solanacearum resistance

“…RLKs were categorized into RD kinases and non-RD kinases according to the RD motif in their kinase domains [70]. By far, well-studied LRR-RLK PRRs, such as FLS2 or Xa21 [71, 72], that recognize the exogenous PAMPs in disease resistance were non-RD kinases [70]. Characterized plant DAMP receptors all contained RD kinase domains [4].…”

Genomic regions on chromosome 5H containing a novel QTL conferring barley yellow dwarf virus-PAV (BYDV-PAV) tolerance in barley

“…A possible candidate gene is HORVU3Hr1G067050 which expresses leucine-rich repeat (LRR) receptor-like protein kinase family protein. LRR receptor-like protein kinase is a type of cell surface receptors represented by receptor(-like) kinases (RKs, RLKs), which consists of extracellular receptor, transmembrane and intracellular protein kinase domains 40 and is involved in plant pathogen defence 41 . Ryd2 not only confers field tolerance as observed in this study, it has also been reported to be capable of reducing virus titre in young plants infected with BYDV-PAV or BYDV-MAV 42,43 .…”

A Pathogen-Responsive Leucine Rich Receptor Like Kinase Contributes to Fusarium Resistance in Cereals

“…hordei ) and stem rust ( Puccinia graminis f. sp. tritici ) resulted in reduced defense genes expression, suggesting a tentative PRR role against these fungal pathogens ( Parrott et al, 2016 ). TaLRRK-6D and HvLRRK-6H add a cereal gene to the list of LRR-RLK sub-family LRR XII genes with proven roles in defense against pathogens; this sub-family also includes Arabidopsis FLS2, Arabidopsis EF-Tu receptor and rice Xa21 ( Shiu et al, 2004 ; Schoonbeek et al, 2015 ; Schwessinger et al, 2015 ; Thomas et al, 2017 ).…”