Applied plant biotechnology for improving resistance to biotic stress

Plants are continuing challenged by varied pathogens, including bacteria, fungi, viruses, and nematodes. Physical barriers such as polysaccharides are the first line of avoidance for pathogens entrance and cell invasion. To protect themselves against the invaders, plants have evolved innate immunity, through several mechanisms, receptor signalling, activation of transcription factors, reactive oxygen species, antimicrobial proteins, RNA silencing, and secondary metabolism components. Plant innate immunity is an efficient defence against plant pathogens. The first level of plant-microorganism interaction is the sensing of Microbial associated molecular patterns (MAMP) by recognising receptors, leading to Pattern triggered immunity (PTI). Non-race-specific inducers of defense are the elicitors, formed by a wide range of different types of molecules. PTI is sensing also Damage Associated Molecular Patterns (DAMPs). Pathogen strains evolved a series of effectors, penetrating the cells, to manipulate and modify a series of host protein targets, Effectors are sensed by Resistance proteins, often in association, a sensor and an executor, or an R guard or trap, sensed by an R executor. The perturbation of host proteins caused by effectors leads to effector-triggered immunity (ETI). Successful perception of a pathogen by PTI or ETI triggers intercellular signalling which results in expression of defence proteins and in the hypersensitive response (HR), or to Systemic Acquired Resistance (SAR). Chapter 1, Plant Leucine rich repeat- receptors for enhanced PAMP- triggered immunity (PTI) and effector triggered immunity (ETI), presents an overview on plant Leucine Rich Repeat (LRR) receptors and resistance genes, their inter-species transfer, the engineering of Resistance proteins, and the biotechnologies applications to reinforce plant species immunity and response toward bacteria, fungi and viruses. Chapter 2, VIGS: virus induced gene silencing and approaches in plant protection, describes post-transcriptional gene silencing (PTGS), during which viral gene expression is severely inhibited. A kind of PTGS, called virus-induced gene silencing (VIGS), is obtained using various virus vectors, and has been applied to research on plant functional genes. The chapter discusses the existing problems and the perspectives of the technology. Chapter 3, Induction and transducing PTI to the field, enters in detail on the receptor activation and signaling pathways. The chapter discusses the opportunities and challenges provided by these approaches to enhance or alter the plant resistance and immunity, the constrains posed by regulatory authorities, the impact on beneficial microorganisms, and the outer membrane vesicles, with prospects to exploit nanovesicles as agrochemicals in crop protection. Chapter 4, NBS-LRR genes - plant health sentinels: structure, roles, evolution and biotechnological applications, introduces information on mechanisms of action, regulation, patterns of expression, subcellular localization, origin, diversification, and evolution in plants. Aspects of plant-pathogen coevolution are discussed, as well as resistance-breaking mechanisms. The chapter presents the -omics technologies, i.e. genomics and transcriptomics, and emergence of the NLRomics, in the annotation and comparative analysis of NBS-LRR members at functional and structural level. Chapter 5, Plant disease resistance gene discovery through use of informatic tools, describes plant genetic repositories, and the application of bioinformatics in the discovery of Resistance proteins, from proteome analysis to motif searches, to R-predictor application, to bibliographic searches, comparative genomics, gene expression analyses, to studies on R-gene-associated markers, to select