Overexpression of LYK4, a lysin motif receptor with non-functional kinase domain, enhances tolerance to Alternaria brassicicola and increases trichome density in Brassica juncea

• Published in: Plant science (Limerick) 2021-08, Vol.309, p.110953-110953, Article 110953
• Main Authors: De, Aishee, Maity, Atanu, Mazumder, Mrinmoy, Mondal, Banani, Mukherjee, Amrita, Ghosh, Swagata, Ray, Pranita, Polley, Smarajit, Dastidar, Shubhra Ghosh, Basu, Debabrata
• Format: Article
• Language: English
• Subjects: Alternaria brassicicola; Brassica juncea; Jasmonic acid; Lysin motif receptor-like kinase 4; Sinapis alba; Trichome development
• ISSN: 0168-9452; 1873-2259
• DOI: 10.1016/j.plantsci.2021.110953

•Lysin motif receptor-like kinase 4 isolated from Brassica juncea, is an inactive kinase, localized to the plasma membrane.•Overexpression (OE) of LYK4 enhanced tolerance against Alternaria brassicicola.•OE also exhibited a trichome dense phenotype with increased methyl jasmonate responsiveness.•Several transcription factors involved in defense and trichome development were significantly upregulated in the OE lines.•LYK4 has a dual functional role in defense and trichome development. Lysin motif receptor-like kinases (LYKs) are involved in the recognition of chitin and activation of plant immune response. In this study, we found LYK4 to be strongly induced in resistant Sinapis alba compared with susceptible Brassica juncea on challenge with Alternaria brassicicola. In silico analysis and in vitro kinase assay revealed that despite the presence of canonical protein kinase fold, B.juncea LYK4 (BjLYK4) lacks several key residues of a prototype protein kinase which renders it catalytically inactive. Transient expression analysis confirmed that fluorescently tagged BjLYK4 localizes specifically to the plasma membrane. Overexpression (OE) of BjLYK4 in B. juncea enhanced tolerance against A. brassicicola. Interestingly, the OE lines also exhibited a novel trichome dense phenotype and increased jasmonic acid (JA) responsiveness. We further showed that many chitin responsive WRKY transcription factors and JA biosynthetic genes were strongly induced in the OE lines on challenge with the pathogen. Moreover, several JA inducible trichome developmental genes constituting the WD-repeat/bHLH/MYB activator complex were also upregulated in the OE lines compared with vector control and RNA interference line. These results suggest that BjLYK4 plays an essential role in chitin-dependent activation of defense response and chitin independent trichome development likely by influencing the JA signaling pathway.