Evolutionary relationships among barley and <i>Arabidopsis</i> core circadian clock and clock-associated genes

The circadian clock regulates a multitude of plant developmental and metabolic processes. In crop species, it contributes significantly to plant performance and productivity and to the adaptation and geographical range over which crops can be grown. To understand the clock in barley and how it relates to the components in the Arabidopsis thaliana clock, we have performed a systematic analysis of core circadian clock and clock-associated genes in barley, Arabidopsis and another eight species including tomato, potato, a range of monocotyledonous species and the moss, Physcomitrella patens. We have identified orthologues and paralogues of Arabidopsis genes which are conserved in all species, monocot/dicot differences, species-specific differences and variation in gene copy number (e.g. gene duplications among the various species). We propose that the common ancestor of barley and Arabidopsis had two-thirds of the key clock components identified in Arabidopsis prior to the separation of the monocot/dicot groups. After this separation, multiple independent gene duplication events took place in both monocot and dicot ancestors. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00239-015-9665-0) contains supplementary material, which is available to authorized users

Physical and genetic mapping of barley (Hordeum vulgare) germin-like cDNAs

Germin with oxalate oxidase and superoxide dismutase activity is a homohexamer of six manganese-containing interlocked β-jellyroll monomers with extreme resistance to heat and proteolytic degradation [Woo, E.-J., Dunwell, J. M., Goodenough, P. W., Marvier, A. C. & Pickersill, R. W. (2000) Nat. Struct. Biol. 7, 1036–1038]. This structure is conserved in germin-like proteins (GLPs) with other enzymatic functions and characteristic for proteins deposited in plant cell walls in response to pathogen attack and abiotic stress. Comparative nucleotide and amino acid sequence analyses of 49,610 barley expressed sequence tags identified 124 germin and germin-like cDNAs, which distributed into five subfamilies designated HvGER-I to HvGER-V. Representative cDNAs for these subfamilies hybridized to 67 bacterial artificial chromosome (BAC) clones from a library containing 6.3 genomic equivalents. Twenty-six BAC clones hybridized to the subfamily IV probe and identified a gene-rich region including clone 418E1 of 96 kb encoding eight GLPs (i.e., 1 gene per 12 kb). This BAC clone lacked highly repeated sequences and mapped to the subtelomeric region of the long arm of chromosome 4(4H). Among the six genes of the contig expressed in leaves, one specifies a protein known to be associated with papilla formation in the epidermis upon powdery mildew infection. Three structural genes for oxalate oxidase are present in subfamily I and eight GLPs of various functions in the other subfamilies. These genes map at loci in chromosomes 1(7H), 2 (2H), 3(3H), 4(4H), and 7(5H). Some are present on a single BAC clone. The results are discussed in relation to cereal genome organization

Changes induced by powdery mildew in the salicylic acid and polyamine contents and the antioxidant enzyme activities of wheat lines

Investigations were made on four wheat (Triticum aestivum L.) lines under greenhouse conditions, in order to reveal the role of stress-protective materials, namely salicylic acid, polyamines and antioxidant enzymes in the level of tolerance to powdery mildew infection caused by Blumeria graminis (DC.) Speer f.sp. tritici Ém. Marchal. The four lines showed different levels of tolerance, assessed on the Saari- Prescott scoring scale: TC26 and TC33 proved to be susceptible and TC9 and TC19 resistant. In most of the lines, infection caused changes in the activities of antioxidant enzymes, especially in the case of guaiacol peroxidase. Four peroxidase isoenzymes, which responded differently to powdery mildew infection could be detected by gel electrophoresis. Infection had only a slight effect on the levels of salicylic acid (free and bound forms) in inoculated plants; while the levels of polyamines, especially spermidine and spermine increased after infection. Correlation analysis was also performed to examine how close a relationship exists between the parameters investigated. It was concluded that salicylic acid, polyamines and antioxidant enzymes have an important role in plant responses and defence mechanisms during this biotic stress and that in some cases there were significant relationships between them