Strigolactones (SLs) represent a class of plant hormones that are involved in inhibiting shoot branching and in promoting abiotic stress responses. There is evidence that the biosynthetic pathways of SLs and abscisic acid (ABA) are functionally connected. However, little is known about the mechanisms underlying the interaction of SLs and ABA, and the relevance of this interaction for shoot architecture. Based on sequence homology, four genes (HvD27, HvMAX1, HvCCD7, and HvCCD8) involved in SL biosynthesis were identified in barley and functionally verified by complementation of Arabidopsis mutants or by virus-induced gene silencing. To investigate the influence of ABA on SLs, two transgenic lines accumulating ABA as a result of RNAi-mediated down-regulation of HvABA 8'-hydroxylase 1 and 3 were employed. LC-MS/MS analysis confirmed higher ABA levels in root and stem base tissues in these transgenic lines. Both lines showed enhanced tiller formation and lower concentrations of 5-deoxystrigol in root exudates, which was detected for the first time as a naturally occurring SL in barley. Lower expression levels of HvD27, HvMAX1, HvCCD7, and HvCCD8 indicated that ABA suppresses SL biosynthesis, leading to enhanced tiller formation in barley.

The root endophytic fungus Piriformospora indica enhances plant adaptation to environmental stress based on general and non-specific plant species mechanisms. In the present study, we integrated the ionomics, metabolomics, and transcriptomics data to identify the genes and metabolic regulatory networks conferring salt tolerance in P. indica-colonized barley plants. To this end, leaf samples were harvested at control (0 mM NaCl) and severe salt stress (300 mM NaCl) in P. indica-colonized and non-inoculated barley plants 4 weeks after fungal inoculation. The metabolome analysis resulted in an identification of a signature containing 14 metabolites and ions conferring tolerance to salt stress. Gene expression analysis has led to the identification of 254 differentially expressed genes at 0 mM NaCl and 391 genes at 300 mM NaCl in P. indica-colonized compared to non-inoculated samples. The integration of metabolome and transcriptome analysis indicated that the major and minor carbohydrate metabolism, nitrogen metabolism, and ethylene biosynthesis pathway might play a role in systemic salt-tolerance in leaf tissue induced by the root-colonized fungus.

Recessive mutations in the Mlo gene confer broad spectrum resistance in barley (Hordeum vulgare) to powdery mildew (Blumeria graminis f. sp. hordei), a widespread and damaging disease. However, all alleles discovered to date also display deleterious pleiotropic effects, including the naturally occurring mlo-11 mutant which is widely deployed in Europe. Recessive resistance was discovered in Eth295, an Ethiopian landrace, which was developmentally controlled and quantitative without spontaneous cell wall appositions or extensive necrosis and loss of photosynthetic tissue. This resistance is determined by two copies of the mlo-11 repeat units, that occur upstream to the wild-type Mlo gene, compared to 11–12 in commonly grown cultivars and was designated mlo-11 (cnv2). mlo-11 repeat unit copy number-dependent DNA methylation corresponded with cytological and macroscopic phenotypic differences between copy number variants. Sequence data indicated mlo-11 (cnv2) formed via recombination between progenitor mlo-11 repeat units and the 3′ end of an adjacent stowaway MITE containing region. mlo-11 (cnv2) is the only example of a moderated mlo variant discovered to date and may have arisen by natural selection against the deleterious effects of the progenitor mlo-11 repeat unit configuration.

S Posters Regulate and be regulated: tight control of plant defence responses by the Arabidopsis transcription factor MYB30 Pierre Buscail, Daniel Marino, Joanne Canonne, Alain Jauneau, Cecile Pouzet, Dominique Roby and Susana Rivas Laboratoire des interactions plantes micro-organismes (LIPM), UMR CNRS-INRA, FRANCE Plant defence responses are often associated to the development of the so-called hypersensitive response (HR), a form of programmed cell death that confines the pathogen to the inoculation site. The sharp boundary of the HR suggests the existence of efficient mechanisms that control cell death and survival. The transcription factor MYB30 is a positive regulator of Arabidopsis defence and HR responses against bacterial pathogens. MYB30 appears to modulate cell death-related lipid signaling by enhancing the synthesis of sphingolipid-containing very long chain fatty acids after bacterial inoculation. Plant and animal pathogenic bacteria inject type III effectors (T3Es) into host cells to suppress host immunity and promote successful infection.We have shown that MYB30 is targeted by the bacterial T3E XopD, resulting in suppression of MYB30-mediated plant defences and underlining the crucial role played by MYB30 in the regulation of plant disease resistance. In addition, the activity of MYB30 is tightly controlled inside plant cells through protein-protein interactions and posttranslational modifications. Our recent work identified a protease of the subtilase family (SBT) as a MYB30interacting partner in yeast. Interestingly, we have shown that the SBT transcript is alternatively spliced, leading to the production of two distinct gene products that encode either a secreted (SBT-1) or a nycleocytoplasmic (SBT-2) protein. The specific interaction between MYB30 and SBT-2 was confirmed in planta using the FRET-FLIM technique. Importantly, analysis of sbt mutant Arabidopsis

Bioinformatics and computational intelligence are undoubtedly remarkably fast growing fields of research and real-world applications with enormous potential for current and future developments. Bioinf

The naturally occurring enantiomer of the various octadecanoids and jasmonates is established in a biosynthetic step catalyzed by the allene oxide cyclase (AOC). The AOC converts an allene oxide formed by an allene oxide synthase (AOS). Here, we show cloning and characterization of cDNAs encoding the AOC and a third AOS, respectively, in addition to the two AOSs previously published (Plant J. 21, 199–213, 2000). The ORF of the AOC-cDNA of 717 bp codes for a protein of 238 amino acid residues carrying a putative chloroplast target sequence. Overexpression without chloroplast target sequence revealed AOC activity. The AOC was found to be a single copy gene which mapped on chromosome 6H. AOC mRNA accumulation appeared in leaf segments upon treatment with various jasmonates, octadecanoids and ABA or during stress such as treatment with sorbitol or glucose solutions. Infection with powdery mildew activated AOC expression in susceptible and resistant lines of barley which correlated with PR1b expression. Among different tissues of barley seedlings, the scutellar node and leaf base accumulated AOC mRNA preferentially which correlated with accumulation of mRNAs for other biosynthetic enzymes (lipoxygenases, AOSs). AOC mRNA accumulation appeared also abundantly in parts of the root containing the tip and correlated with elevated levels of jasmonates. The data suggest a link of AOC expression and JA formation and support role of JA in stress responses and development of barley.

Jasmonic acid or its methyl ester induce de novo synthesis of a number of proteins of mostly unknown function in barley (Hordeum vulgare L.). In a topical spray application, 30 [mu]g of jasmonic acid per plant effectively protected barley against subsequent infection by Erysiphe graminis f.sp. hordei. Examination of jasmonic acid-induced barley proteins revealed the presence of several acid-soluble (pH 2.8) proteins. Two prominent groups of 25 kD and 10 to 12 kD apparent molecular mass were present in the intercellular washing fluid. The set of extracellular, induced proteins showed no similarity to barley pathogenesis-related proteins. An in vivo test against E. graminis revealed no antifungal activity of the extracellular jasmonic acid-induced proteins. Experiments with the transcription inhibitor cordycepin showed no correlation between accumulation of jasmonic acid-induced proteins and protection. The application of jasmonic acid and E. graminis simultaneously resulted in independent extracellular accumulation of both jasmonic acid-induced proteins and of pathogenesis-related proteins. The data suggest that jasmonic acid directly inhibits appressoria differentiation of the fungus, and that it is not involved in the signal transduction mechanism leading to induction of pathogenesis-related proteins.