Molecular analysis of three new receptor‐like kinase genes from hexaploid wheat and evidence for their participation in the wheat hypersensitive response to stripe rust fungus infection

Abstract

SummaryConsiderable progress has been made in understanding the function of receptor-like kinase (RLK) genes in model plants. However, much less is known about these genes in crop species. Here we report the characterization of three new wheat RLK genes (TaRLK-R1, 2 and 3). The primary structure of the putative proteins TaRLK-R1, 2 and 3 contained a signal peptide, a cysteine-rich extracellular domain, a transmembrane domain, and a predicted intracellular kinase domain. The fusions between TaRLK-R1, 2 or 3 and the green fluorescence protein (GFP) were targeted to the plasma membrane; such targeting required the signal peptide, extracellular domain and transmembrane domain. Transcription of TaRLK-R1, 2 and 3 was found mainly in the green organs, and was regulated by light. Transcript levels of TaRLK-R1, 2 and 3 increased during the hypersensitive reaction (HR) to stripe rust fungus. In addition, the TaRLK-R3 transcript level was also upregulated by abiotic stresses. Further experiments revealed that the recombinant kinase domain of TaRLK-R3 exhibited auto-phosphorylation activity in vitro. Knocking down the transcript levels of TaRLK-R1, 2 or 3 individually or all together by virus-induced gene silencing compromised the wheat HR to stripe rust fungus. The demonstration of TaRLK-R1, 2 and 3 as positive contributors in the wheat HR to stripe rust fungus suggests a new direction for further functional studies of this important family of RLK genes, and may facilitate the breeding of wheat varieties resistant to stripe rust disease.

Resources for Virus-Induced Gene Silencing in the Grasses

“…This pattern of silencing has proven sufficient to allow the initiation of VIGS and the subsequent challenge of silenced tissue with a pathogen. In this way, BSMV-VIGS has been used to demonstrate the functional requirement of particular genes for resistance in a wide range of grass disease systems, including the wheat Lr21-mediated leaf rust resistance pathway (Scofield et al, 2005), the wheat stripe rust resistance pathway (Zhou et al, 2007), the barley Mla13 pathway (Hein et al, 2005), and nonhost resistance of barley to Cochliobolus carbonum race 1 (Sindhu et al, 2008).…”

Serine/threonine kinase gene Stpk-V , a key member of powdery mildew resistance gene Pm21 , confers powdery mildew resistance in wheat

“…VIGS was mediated by BSMV (17). Vector construction, plasmid linearization, in vitro transcription, and virus infection were conducted as described by Wang et al (18) and Zhou et al (33). Details are provided in SI Materials and Methods.…”

RNA interference for wheat functional gene analysis

“…Other recent examples include the BSMV-VIGS silencing of the leaf rust resistance gene Lr1 candidate gene, RGA567-5 (Cloutier et al 2007), and of three receptor-like kinase genes (TaRLK) conferring resistance to Puccinia striiformis f. sp. tritici, the causal agent of stripe rust (Zhou et al 2007). These examples suggest that the BSMV-VIGS system has the potential to aid in the functional analysis of wheat disease resistance genes, among others.…”