The barley UNICULM2 gene resides in a centromeric region and may be associated with signaling and stress responses.

Vegetative axillary meristem (AXM) activity results in the production of branches. In barley (Hordeum vulgare L.), vegetative AXM develop in the crown and give rise to modified branches, referred to as tillers. Mutations in the barley low-tillering mutant uniculm2 block vegetative AXM development and prevent tiller development. The objectives of this work were to examine gene expression in wild-type and cul2 mutant plants, fine map the CUL2 gene, and to examine synteny in the CUL2 region in barley with rice. RNA profiling experiments using two near-isogenic line pairs carrying either the cul2 mutant allele or wild-type CUL2 allele in different genetic backgrounds detected 28 unique gene transcripts exhibiting similar patterns of differential accumulation in both genetic backgrounds, indicating that we have identified key genes impacted by the CUL2 gene. Twenty-four genes had higher abundance in uniculm2 mutant tissues, and nearly half of the annotated genes likely function in stress-response or signal transduction pathways. Genetic mapping identified five co-segregating markers in 1,088 F2 individuals. These markers spanned the centromere region on chromosome 6H, and coincided with a 50-cM region on rice chromosome 2, indicating that it may be difficult to positionally clone CUL2. Taken together, the results revealed stress response and signal transduction pathways that are associated with the CUL2 gene, isolating CUL2 via positional cloning approaches that may be difficult, and the remnants of barley-rice synteny in the CUL2 region.

Transcriptome analysis of the barley-Fusarium graminearum interaction.

Fusarium head blight (FHB) of barley (Hordeum vulgare L.) is caused by Fusarium graminearum. FHB causes yield losses and reduction in grain quality primarily due to the accumulation of trichothecene mycotoxins such as deoxynivalenol (DON). To develop an understanding of the barley-F. graminearum interaction, we examined the relationship among the infection process, DON concentration, and host transcript accumulation for 22,439 genes in spikes from the susceptible cv. Morex from 0 to 144 h after F. graminearum and water control inoculation. We detected 467 differentially accumulating barley gene transcripts in the F. graminearum-treated plants compared with the water control-treated plants. Functional annotation of the transcripts revealed a variety of infection-induced host genes encoding defense response proteins, oxidative burst-associated enzymes, and phenylpropanoid pathway enzymes. Of particular interest was the induction of transcripts encoding potential trichothecene catabolic enzymes and transporters, and the induction of the tryptophan biosynthetic and catabolic pathway enzymes. Our results define three stages of E graminearum infection. An early stage, between 0 and 48 h after inoculation (hai), exhibited limited fungal development, low DON accumulation, and little change in the transcript accumulation status. An intermediate stage, between 48 and 96 hai, showed increased fungal development and active infection, higher DON accumulation, and increased transcript accumulation. A majority of the host gene transcripts were detected by 72 hai, suggesting that this is an important timepoint for the barley-F. graminearum interaction. A late stage also identified between 96 and 144 hai, exhibiting development of hyphal mats, high DON accumulation, and a reduction in the number of transcripts observed. Our study provides a baseline and hypothesis-generating dataset in barley during F. graminearum infection and in other grasses during pathogen infection.

Functional and comparative bioinformatic analysis of expressed genes from wheat spikes infected with Fusarium graminearum.

Fusarium head blight, caused by the fungus Fusarium graminearum, is a major disease on wheat (Triticum aestivum L.). Expressed sequence tags (ESTs) were used to identify genes expressed during the wheat-F. graminearum interaction. We generated 4,838 ESTs from a cDNA library prepared from spikes of the partially resistant cultivar Sumai 3 infected with F. graminearum. These ESTs were composed of 2,831 singlet (single-copy transcripts) and 715 contigs (multiple-copy transcripts) for a total of 3,546 non-redundant sequences. Four sets of nonredundant sequences were identified. One set contains numerous, common biotic and abiotic stress-related genes. Many of these stress-related genes were represented by multiple ESTs, indicating that they are abundantly expressed. A second set comprised 16 nonredundant sequences from F. graminearum that may be required for pathogenicity. A subset of these fungal genes encodes proteins associated with plant cell wall degradation. A third set of 326 nonredundant sequences had no DNA or amino acid sequence similarity to almost 1 million plant and over 7 million animal sequences in dbEST (as of 22 June 2001). Thus, these 326 nonredundant sequences have only been found in our F. graminearum-infected 'Sumai 3' cDNA library. A fourth set of 29 nonredundant sequences was found in our F. graminearum-infected wheat and another plant-pathogen interaction cDNA library. Some of these sequences encode proteins that may act in establishing various plant-fungal interactions.