Deployment of fast-evolving disease-resistance genes is one of the most successful strategies used by plants to fend off pathogens. In gene-for-gene relationships, most cloned disease-resistance genes encode intracellular nucleotide-binding leucine-rich-repeat proteins (NLRs) recognizing pathogen-secreted isolate-specific avirulence (Avr) effectors delivered to the host cytoplasm. This process often triggers a localized hypersensitive response, which halts further disease development . Here we report the map-based cloning of the wheat Stb6 gene and demonstrate that it encodes a conserved wall-associated receptor kinase (WAK)-like protein, which detects the presence of a matching apoplastic effector and confers pathogen resistance without a hypersensitive response . This report demonstrates gene-for-gene disease resistance controlled by this class of proteins in plants. Moreover, Stb6 is, to our knowledge, the first cloned gene specifying resistance to Zymoseptoria tritici, an important foliar fungal pathogen affecting wheat and causing economically damaging septoria tritici blotch (STB) disease.

cDNA corresponding to the GA4 gene of Arabidopsis thaliana L. (Heynh.) was expressed in Escherichia coli, from which cell lysates converted [14 C]gibberellin (GA) 9 and [ 14 C]GA 20 to radiolabeled GA 4 and GA 1 , respectively, thereby confirming that GA4 encodes a GA 3␤-hydroxylase. GA 9 was the preferred substrate, with a Michaelis value of 1 M compared with 15 M for GA 20 . Hydroxylation of these GAs was regiospecific, with no indication of 2␤-hydroxylation or 2,3-desaturation. The capacity of the recombinant enzyme to hydroxylate a range of other GA substrates was investigated. In general, the preferred substrates contained a polar bridge between C-4 and C-10, and 13-deoxy GAs were preferred to their 13-hydroxylated analogs. Therefore, no activity was detected using GA 12 -aldehyde, GA 12 , GA 19 , GA 25 , GA 53 , or GA 44 as the open lactone (20-hydroxy-GA 53 ), whereas GA 15 , GA 24 , and GA 44 were hydroxylated to GA 37 , GA 36 , and GA 38 , respectively. The open lactone of GA 15 (20-hydroxy-GA 12 ) was hydroxylated but less efficiently than GA 15 . In contrast to the free acid, GA 25 19,20-anhydride was 3␤-hydroxylated to give GA 13 . 2,3-Didehydro-GA 9 and GA 5 were converted by recombinant GA4 to the corresponding epoxides 2,3-oxido-GA 9 and GA 6 .

Mutagenesis is an important tool in crop improvement. However, the hexaploid genome of wheat (Triticum aestivum L.) presents problems in identifying desirable genetic changes based on phenotypic screening due to gene redundancy. TILLING (Targeting Induced Local Lesions IN Genomes), a powerful reverse genetic strategy that allows the detection of induced point mutations in individuals of the mutagenized populations, can address the major challenge of linking sequence information to the biological function of genes and can also identify novel variation for crop breeding. Wheat is especially well-suited for TILLING due to the high mutation densities tolerated by polyploids. However, only a few wheat TILLING populations are currently available in the world, which is far from satisfying the requirement of researchers and breeders in different growing environments. In addition, current TILLING screening protocols require costly fluorescence detection systems, limiting their use, especially in developing countries. We developed a new TILLING resource comprising 2610 M2 mutants in a common wheat cultivar ‘Jinmai 47’. Numerous phenotypes with altered morphological and agronomic traits were observed from the M2 and M3 lines in the field. To simplify the procedure and decrease costs, we use unlabeled primers and either non-denaturing polyacrylamide gels or agarose gels for mutation detection. The value of this new resource was tested using PCR with RAPD and Intron-spliced junction (ISJ) primers, and also TILLING in three selected candidate genes, in 300 and 512 mutant lines, revealing high mutation densities of 1/34 kb by RAPD/ISJ analysis and 1/47 kb by TILLING. In total, 31 novel alleles were identified in the 3 targeted genes and confirmed by sequencing. The results indicate that this mutant population represents a useful resource for the wheat research community. We hope that the use of this reverse genetics resource will provide novel allelic diversity for wheat improvement and functional genomics.

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Soluble enzyme preparations from embryos and endosperm of Marah macrocarpus (previously Echinocysfis macrocarpa) were incubated with ['4C,1gibberellin