Multifaceted Strategies Used by Root-Knot Nematodes to Parasitize Plants-A Review

Root-knot nematodes being omnipresent in agricultural and horticultural soils are tallied among the most important economic pathogens around the world.For successful parasitism,these nematodes use various strategies to control and manipulate the host plant’s cell machinery.These strategies include the mole-cular mimicry of some host genes by some nematode secreted effector proteins,secretion of cell wall digesting enzymes and other effector proteins that are responsible for the suppression of defence by the host plant.All these secretions which are released through the stylet,contribute to the formation of specialized feeding sites or giant cells.The effector proteins interfere with the normal physiology,cytology and biochemistry of the host plant.The present review brings novel insights by summarizing some novel effectors that have been discovered recently like MgPDI,MiMIF,MiIDL1,MiISE6,Mg16820,etc.It also discusses some novel mechanisms through which these effector proteins target different pathways of host plants and thus facilitate nematode parasitism.

Two NIS1-like proteins from apple canker pathogen(Valsa mali)play distinct roles in plant recognition and pathogen virulence

Conserved effectors produced by phytopathogens play critical roles in plant-microbe interactions.NIS1-like proteins represent a newly identified family of effectors distributed in multiple fungal species.However,their biological functions in a majority of pathogenic fungi remain largely elusive and require further investigation.In this study,we characterized two NIS1-like proteins VmNIS1 and VmNIS2 from Valsa mali,the causal agent of apple Valsa canker.Both of these two proteins were predicted to be secreted.Using agroinfiltration,we found that VmNIS1 induced intense cell death,whereas VmNIS2 suppressed INF1 elicitin-triggered cell death in Nicotiana benthamiana.Treatment of N.benthamiana with VmNIS1 recombinant protein produced by Escherichia coli activated a series of immune responses and enhanced plant disease resistance against Phytophthora capsici.In contrast,VmNIS2 suppressed plant immune responses and promoted P.capsici infection when transiently expressed in N.benthamiana.Both VmNIS1 and VmNIS2 were shown to be highly induced at late stage of V.mali infection.By individually knocking out of these two genes in V.mali,however,only VmNIS2 was shown to be required for pathogen virulence as well as tolerance to oxidative stress.Notably,we further showed that C-terminal extension of VmNIS1 was essential for plant recognition and VmNIS2 may escape plant detection via sequence truncation.Our data collectively indicate that VmNIS1 and VmNIS2 play distinct roles in plant recognition and pathogen virulence,which provided new insights into the function of NIS1-like proteins in plant-microbe interactions.

Pathogen-informed breeding for crop disease resistance

The development of durable and broad-spectrum resistance is an economical and eco-friendly approach to control crop diseases for sustainable agricultural production. Emerging knowledge of the molecular basis of pathogenesis and plant–pathogen interactions has contributed to the development of novel pathogen-informed breeding strategies beyond the limits imposed by conventional breeding. Here,we review the current status of pathogen-assisted resistance-related gene cloning. We also describe how pathogen effector proteins can be used to identify resistance resources and to inform cultivar deployment. Finally, we summarize the main approaches for pathogen-directed plant improvement,including transgenesis and genome editing. Thus, we describe the emerging role of pathogen-related studies in the breeding of disease-resistant varieties, and propose innovative pathogen-informed strategies for future applications.