Plant MLO proteins: Conserved "disease susceptibility factors" for powdery mildew fungi

Powdery mildew is a widespread plant disease of temperate climates that is caused by ascomycete fungi of the order Erysiphales. The disease is macroscopically characterized by “powdery” fungal reproduction structures on the surface of plant organs. It is an important threat for both agri- and horticulture and can cause significant harvest losses in cereals and crop plants such as wheat, barley, and tomato, and severely impact ornamental plants such as roses. Accordingly, the generation of plant breeds that exhibit robust immunity to this disease is of great economic interest. One major step in this direction was the discovery of barley mutant plants that display near complete resistance to the barley powdery mildew pathogen, Blumeria graminis f.sp. hordei (Bgh). These plants, which carry recessively inherited loss-of-function mutations in the gene Mildew resistance locus o (Mlo), show durable broad-spectrum resistance against virtually all Bgh isolates. On mlo mutant plants, powdery mildew pathogenesis is terminated at the stage of cell wall penetration and host cell entry; consequently, fungal sporelings do not form haustoria inside host cells and fungal colonies cannot develop. Subsequent studies revealed that (1) Mlo genes are restricted to plants and green algae and represented as small to medium-sized families in higher plant species and (2) that mlo-based powdery mildew resistance is not restricted to the monocot barley, but also found in the distantly related eudicot plant species Arabidopsis thaliana. Mutant alleles of Arabidopsis thaliana AtMLO2, one out of the 15 MLO genes present in the Arabidopsis genome, confers partial resistance to the adapted powdery mildew species Golovinomyces orontii and G. cichoracearum.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

The visible touch: in planta visualization of protein-protein interactions by fluorophore-based methods

Non-invasive fluorophore-based protein interaction assays like fluorescence resonance energy transfer (FRET) and bimolecular fluorescence complementation (BiFC, also referred to as "split YFP") have been proven invaluable tools to study protein-protein interactions in living cells. Both methods are now frequently used in the plant sciences and are likely to develop into standard techniques for the identification, verification and in-depth analysis of polypeptide interactions. In this review, we address the individual strengths and weaknesses of both approaches and provide an outlook about new directions and possible future developments for both techniques

Kanlı bebek

Gaston Leroux'nun Akşam'da yayımlanan Kanlı Bebek adlı romanının ilk ve son tefrikalar

Novel induced mlo mutant alleles in combination with site-directed mutagenesis reveal functionally important domains in the heptahelical barley Mlo protein

<p>Abstract</p> <p>Background</p> <p>Recessively inherited natural and induced mutations in the barley <it>Mlo </it>gene confer durable broad-spectrum resistance against the powdery mildew pathogen, <it>Blumeria graminis </it>f.sp. <it>hordei</it>. <it>Mlo </it>codes for a member of a plant-specific family of polytopic integral membrane proteins with unknown biochemical activity. Resistant barley <it>mlo </it>mutant alleles identify amino acid residues that are critical for Mlo function in the context of powdery mildew susceptibility.</p> <p>Results</p> <p>We molecularly analyzed a novel set of induced barley <it>mlo </it>mutants and used site-directed mutagenesis in combination with transient gene expression to unravel novel amino acid residues of functional significance. We integrate these results with previous findings to map functionally important regions of the heptahelical Mlo protein. Our data reveal the second and third cytoplasmic loop as being particularly sensitive to functional impediment by mutational perturbation, suggesting that these regions are critical for the susceptibility-conferring activity of the Mlo protein. In contrast, only mutations in the second but not the third cytoplasmic loop appear to trigger the Endoplasmic Reticulum-localized quality control machinery that ensures the biogenesis of properly folded membrane proteins.</p> <p>Conclusion</p> <p>Our findings identify functionally important regions of the polytopic barley Mlo protein and reveal the differential sensitivity of individual protein domains to cellular quality control.</p

Rapid evolution in plant-microbe interactions - a molecular genomics perspective

Rapid (co-)evolution at multiple timescales is a hallmark of plant-microbe interactions. The mechanistic basis for the rapid evolution largely rests on the features of the genomes of the interacting partners involved. Here, we review recent insights into genomic characteristics and mechanisms that enable rapid evolution of both plants and phytopathogens. These comprise fresh insights in allelic series of matching pairs of resistance and avirulence genes, the generation of novel pathogen effectors, the recently recognised small RNA warfare, and genomic aspects of secondary metabolite biosynthesis. In addition, we discuss the putative contributions of permissive host environments, transcriptional plasticity and the role of ploidy on the interactions. We conclude that the means underlying the rapid evolution of plant-microbe interactions are multifaceted and depend on the particular nature of each interaction

Evidence for Allele-Specific Levels of Enhanced Susceptibility of Wheat mlo Mutants to the Hemibiotrophic Fungal Pathogen Magnaporthe oryzae pv. Triticum

Barley mlo mutants are well known for their profound resistance against powdery mildew disease. Recently, mlo mutant plants were generated in hexaploid bread wheat (Triticum aestivum) with the help of transgenic (transcription-activator-like nuclease, TALEN) and non-transgenic (targeted induced local lesions in genomes, TILLING) biotechnological approaches. While full-gene knockouts in the three wheat Mlo (TaMlo) homoeologs, created via TALEN, confer full resistance to the wheat powdery mildew pathogen (Blumeria graminis f.sp. tritici), the currently available TILLING-derived Tamlo missense mutants provide only partial protection against powdery mildew attack. Here, we studied the infection phenotypes of TALEN- and TILLING-derived Tamlo plants to the two hemibiotrophic pathogens Zymoseptoria tritici, causing Septoria leaf blotch in wheat, and Magnaporthe oryzae pv. Triticum (MoT), the causal agent of wheat blast disease. While Tamlo plants showed unaltered outcomes upon challenge with Z. tritici, we found evidence for allele-specific levels of enhanced susceptibility to MoT, with stronger powdery mildew resistance correlated with more invasive growth by the blast pathogen. Surprisingly, unlike barley mlo mutants, young wheat mlo mutant plants do not show undesired pleiotropic phenotypes such as spontaneous callose deposits in leaf mesophyll cells or signs of early leaf senescence. In conclusion, our study provides evidence for allele-specific levels of enhanced susceptibility of Tamlo plants to the hemibiotrophic wheat pathogen MoT

Arabidopsis MLO2 is a negative regulator of sensitivity to extracellular reactive oxygen species

The atmospheric pollutant ozone (O-3) is a strong oxidant that causes extracellular reactive oxygen species (ROS) formation, has significant ecological relevance, and is used here as a non-invasive ROS inducer to study plant signalling. Previous genetic screens identified several mutants exhibiting enhanced O-3 sensitivity, but few with enhanced tolerance. We found that loss-of-function mutants in Arabidopsis MLO2, a gene implicated in susceptibility to powdery mildew disease, exhibit enhanced dose-dependent tolerance to O-3 and extracellular ROS, but a normal response to intracellular ROS. This phenotype is increased in a mlo2 mlo6 mlo12 triple mutant, reminiscent of the genetic redundancy of MLO genes in powdery mildew resistance. Stomatal assays revealed that enhanced O-3 tolerance in mlo2 mutants is not caused by altered stomatal conductance. We explored modulation of the mlo2-associated O-3 tolerance, powdery mildew resistance, and early senescence phenotypes by genetic epistasis analysis, involving mutants with known effects on ROS sensitivity or antifungal defence. Mining of publicly accessible microarray data suggests that these MLO proteins regulate accumulation of abiotic stress response transcripts, and transcript accumulation of MLO2 itself is O-3 responsive. In summary, our data reveal MLO2 as a novel negative regulator in plant ROS responses, which links biotic and abiotic stress response pathways.Peer reviewe

VII Jornadas de Expania

Sección: Noticias. Noticias externasLos días 27 y 28 de mayo se celebraron en Santiago de Compostela las VII Jornadas de Expania, la Asociación de Usuarios de Ex Libris en España.N