Molecular genetics and evolution of disease resistance in cereals

Abstract

Contents 320I.320II.321III.321IV.322V.324VI.328VII.329330References330 Summary Cereal crops produce a large part of the globally consumed food and feed. Because of the constant presence of devastating pathogens, the molecular characterization of disease resistance is a major research area and highly relevant for breeding. There has been recent and accelerating progress in the understanding of three distinct resistance mechanisms in cereals: resistance conferred by plasma membrane‐localized receptor proteins; race‐specific resistance conferred by intracellular immune receptors; and quantitative disease resistance. Intracellular immune receptors provide a particularly rich source for evolutionary studies, and have, for example, resulted in the recent discovery of a novel detection mechanism based on integrated decoy domains. Evolutionary studies have also revealed the origins of active resistance genes in both wild progenitors of today's cereals as well as in cultivated forms. In addition, independent evolution of orthologous genes in related cereals has resulted in resistance to different pathogen species. Quantitative resistance genes have been best characterized in wheat. The quantitative resistance genes identified so far in wheat encode transporter proteins or unusual kinase proteins. The recent discoveries in these three different resistance mechanisms have contributed to the basic molecular understanding of cereal immunity against pathogens and have suggested novel applications for resistance breeding.

Genome‐wide scans of selection highlight the impact of biotic and abiotic constraints in natural populations of the model grass Brachypodium distachyon

“…The plant immune system machinery is complex and is composed of two tiers of extracellular and intracellular receptors (Krattinger and Keller, ,b) that efficiently detect the presence of pathogens (for review, see Greeff et al ., ; Couto and Zipfel, ; Eckardt, ). In this study, we found a significant enrichment of signals of selection at genes involved in this first level of defense in the eastern population.…”

An overview of genetic rust resistance: From broad to specific mechanisms

“…The recent development of NLR gene capture approaches promises to rapidly expand the repertoire of cloned rust-resistance genes [11]. To date, 9 wheat genes conferring resistance to leaf ( Lr1 , Lr21 , and Lr10 ), stem ( Sr22 , Sr33 , Sr35 , Sr45 , and Sr50 ), and stripe or yellow ( Yr10 ) rust pathogens have been cloned and all encode NLR receptor proteins [3, 11, 12]. The barley resistance to P .…”

“…As implied, non–race-specific resistance is defined as operating against all races of a pathogen species and is sometimes effective against multiple pathogens [3,12]. Such resistance is generally quantitative, involving a partial resistance phenotype in which the pathogen growth is slowed without an obvious immune response (Fig 1B).…”

Prediction and analysis of three gene families related to leaf rust (Puccinia triticina) resistance in wheat (Triticum aestivum L.)

“…We have already mentioned genes within the STP transporter family like Lr67 . Additional genes include those encoding unusual kinases, receptor-like kinases (RLKs) and receptor-like proteins (RLPs) [69], and genes involving cell wall biosynthesis and metabolism, such as cysteine proteinase, phenylalanine ammonia-lyase, plasma membrane ATPase and chalcone synthase [58]. When a pathogen attacks its host, the first line of host defense is through secretion of cell surface pattern-recognition receptors (PRRs) and such defense-induced proteins may be recognized and overcome by specific pathogen effectors.…”