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Summary Plants have evolved a sophisticated immunity system for specific detection of pathogens and rapid induction of measured defences. Over‐ or constitutive activation of defences would negatively affect plant growth and development. Hence, the plant immune system is under tight positive and negative regulation. MAP kinase phosphatase1 (MKP1) has been identified as a negative regulator of plant immunity in model plantArabidopsis. However, the molecular mechanisms by which MKP1 regulates immune signalling in wheat (Triticum aestivum) are poorly understood. In this study, we investigated the role of TaMKP1 in wheat defence against two devastating fungal pathogens and determined its subcellular localization. We demonstrated that knock‐down ofTaMKP1by CRISPR/Cas9 in wheat resulted in enhanced resistance to rust caused byPuccinia striiformisf. sp.tritici(Pst) and powdery mildew caused byBlumeria graminisf. sp.tritici(Bgt), indicating thatTaMKP1negatively regulates disease resistance in wheat. Unexpectedly, whileTamkp1mutant plants showed increased resistance to the two tested fungal pathogens they also had higher yield compared with wild‐type control plants without infection. Our results suggested that TaMKP1 interacts directly with dephosphorylated and activated TaMPK3/4/6, and TaMPK4 interacts directly with TaPAL. Taken together, we demonstrated TaMKP1 exert negative modulating roles in the activation of TaMPK3/4/6, which are required for MAPK‐mediated defence signalling. This facilitates our understanding of the important roles of MAP kinase phosphatases and MAPK cascades in plant immunity and production, and provides germplasm resources for breeding for high resistance and high yield. 

Crop diseases are responsible for substantial yield losses worldwide, thereby threatening global food security. In this Research Topic, a collection of high-quality articles reported recent research progress concerning genes, proteins, secondary metabolites involved in the interactions between crop plants and their pathogens as well as utilization of new synthetic chemicals in control of crop diseases. As co-editors of this research topic, we appreciate the contributions from the authors of the papers published under this topic and highlight the three themes drawn from their research findings. 

Plant subtilases (SBTs) or subtilisin-like proteases comprise a very diverse family of serine peptidases that participates in a broad spectrum of biological functions. Despite increasing evidence for roles of SBTs in plant immunity in recent years, little is known about wheat (Triticum aestivum) SBTs (TaSBTs). Here, we identified 255 TaSBT genes from bread wheat using the latest version 2.0 of the reference genome sequence. The SBT family can be grouped into five clades, from TaSBT1 to TaSBT5, based on a phylogenetic tree constructed with deduced protein sequences. In silico protein-domain analysis revealed the existence of considerable sequence diversification of the TaSBT family which, together with the local clustered gene distribution, suggests that TaSBT genes have undergone extensive functional diversification. Among those TaSBT genes whose expression was altered by biotic factors, TaSBT1.7 was found to be induced in wheat leaves by chitin and flg22 elicitors, as well as six examined pathogens, implying a role for TaSBT1.7 in plant defense. Transient overexpression of TaSBT1.7 in Nicotiana benthamiana leaves resulted in necrotic cell death. Moreover, knocking down TaSBT1.7 in wheat using barley stripe mosaic virus-induced gene silencing compromised the hypersensitive response and resistance against Puccinia striiformis f. sp. tritici, the causal agent of wheat stripe rust. Taken together, this study defined the full complement of wheat SBT genes and provided evidence for a positive role of one particular member, TaSBT1.7, in the incompatible interaction between wheat and a stripe rust pathogen.