LAUSR

barley Manqi Zhang, Yajin Ye* Key Laboratory of Forest Genetics and Biotechnology, Ministry of Education of China, CoInnovation Center for the Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing, 210037, China. *Author for correspondence: [email protected] Plants have multi-layered defense responses to ward off invading pathogens. The first line of defense is initiated by plant recognition of pathogen-associated molecular patterns (PAMPs), also known as PAMP-triggered immunity, which is mediated by plant pattern recognition receptors (DeFalco et al., 2021). Pattern recognition receptors are usually transmembrane receptor-like kinases or receptor-like proteins that directly interact with PAMPs. The perception of PAMPs by their receptors triggers multiple early defense responses, including calcium flux, activation of mitogen-activated protein kinases (MAPKs), production of reactive oxygen species (ROS), transcriptional reprogramming, callose deposition, and cell-wall strengthening (DeFalco et al., 2021; Kong et al., 2012; Li et al., 2022). In early plant defense responses, MAPK cascades play important roles in transducing signals from upstream sensors/receptors to downstream targets. In Arabidopsis (Arabidopsis thaliana), perception of PAMP signals by their receptors leads to the activation of at least two MAPK cascades. MPK3 and MPK6, which are phosphorylated by common upstream kinases, function together in one of the two MAPK cascades. MPK3 and MPK6 are activated in response to all PAMPs reported to date, and their functions have been characterized in several plant species, such as Arabidopsis, rice (Oryza sativa), tobacco (Nicotiana benthamiana), and tomato (Solanum lycopersicum) (Kong et al., 2012; Liu et al., 2007; Mao et al., 2011). In this issue of Plant Physiology, Basheer et al. (2022) investigated the function of MPK3 in barley (Hordeum vulgare) during Fusarium graminearum infection. Using genetic, physiological, and proteomic data, their results showed that HvMPK3 knockout mutants exhibit higher root resistance to F. graminearum, possibly due to lower ROS