Species relationship in the Pennisetum gene pool: enzyme polymorphism

Summary Variation in leaf esterases (EST), 6-phosphogluconate dehydrogenase (PGD), shikimate dehydrogenase (SKDH), leucine aminopeptidase (AMP), phosphoglucomutase (PGM) and malate dehydrogenase (MDH) is reported in the Pennisetum gene pool. In the primary gene pool, polymorphism for EST, AMP, SKDH was very high, as compared to the near-monomorphic isozymes of PGD. Two loci controlling leaf esterases Est-1 and Est-2, were identified in the primary gene pool. Differences in allelic frequency distribution of the polymorphic Est-1 locus occur between the cultivated and wild pearl millet. The prevalent alleles of Est-1 are absent in P. purpureum Schumach (secondary gene pool). A monomorphic band of the -esterase-specific Est-2 locus was identified in most of the secondary gene pool accessions, P. squamulatum Fresen and an accession of P. pedicellatum. SKDH and EST revealed differences between most of the tertiary gene pool species. By contrast, a PGD zymogram was prevalent in several species of different sectional taxa. Gene duplication for PGD isozymes occurs in the diploid species, P. ramosum, of the tertiary gene pool. Heterodimers of PGD and EST were observed in the hybrid between pearl millet and P. squamulatum, whereas a monomeric structure characterized SKDH and AMP.     

Disomic Thinopyrum intermedium addition lines in wheat with barley yellow dwarf virus resistance and with rust resistances.

Zhong 5 is a partial amphiploid (2n = 56) between Triticum aestivum (2n = 42) and Thinopyrum intermedium (2n = 42) carrying all the chromosomes of wheat and seven pairs of chromosomes from Th. intermedium. Following further backcrossing to wheat, six independent stable 2n = 44 lines were obtained representing 4 disomic chromosome addition lines. One chromosome confers barley yellow dwarf virus (BYDV) resistance, whereas two other chromosomes carry leaf and stem rust resistance; one of the latter also confers stripe rust resistance. Using RFLP and isozyme markers we have shown that the extra chromosome in the Zhong 5-derived BYDV resistant disomic addition lines (Z1, Z2, or Z6) belongs to the homoeologous group 2. It therefore carries a different locus to the BYDV resistant group 7 addition, L1, described previously. The leaf, stem, and stripe rust resistant line (Z4) carries an added group 7 chromosome. The line Z3 has neither BYDV nor rust resistance, is not a group 2 or group 7 addition, and is probably a group 1 addition. The line Z5 is leaf and stem rust resistant, is not stripe rust resistant, and its homoeology remains unknown.     

Molecular-genetic maps for group 1 chromosomes of Triticeae species and their relation to chromosomes in rice and oat

Group 1 chromosomes of the Triticeae tribe have been studied extensively because many important genes have been assigned to them. In this paper, chromosome 1 linkage maps of Triticum aestivum, T. tauschii, and T. monococcum are compared with existing barley and rye maps to develop a consensus map for Triticeae species and thus facilitate the mapping of agronomic genes in this tribe. The consensus map that was developed consists of 14 agronomically important genes, 17 DNA markers that were derived from known-function clones, and 76 DNA markers derived from anonymous clones. There are 12 inconsistencies in the order of markers among seven wheat, four barley, and two rye maps. A comparison of the Triticeae group 1 chromosome consensus map with linkage maps of homoeologous chromosomes in rice indicates that the linkage maps for the long arm and the proximal portion of the short arm of group 1 chromosomes are conserved among these species. Similarly, gene order is conserved between Triticeae chromosome 1 and its homoeologous chromosome in oat. The location of the centromere in rice and oat chromosomes is estimated from its position in homoeologous group 1 chromosomes of Triticeae.     

The cre1 and cre3 nematode resistance genes are located at homeologous loci in the wheat genome

Differential responses in host-nematode pathotype interactions occur in wheat lines carrying different cereal cyst nematode resistance (Cre) genes. Cre1, located on chromosome 2B, confers resistance to most European nematodes and the sole Australian pathotype, while Cre3, present on chromosome 2D, is highly resistant to the Australian pathotype and susceptible to a number of European pathotypes. Genes encoding nucleotide binding site-leucine rich repeat (NBS-LRR) proteins that cosegregate with the Cre3 locus cross hybridize to homologues whose restriction fragment length polymorphism (RFLP) patterns distinguish near-isogenic Cre1 nematode-resistant wheat lines. Genetic mapping showed that the NBS-LRR gene members that distinguished the Cre1 near-isogenic lines were located on chromosome 2BL at a locus, designated Xcsl107, that cosegregates with the Cre1 locus. A haplotype of NBS-LRR genes from the Xcsl107 locus provides a diagnostic marker for the presence of Cre1 nematode resistance in a wide collection of wheat lines and segregating families. Genetic analysis of NBS-LRR haplotypes that cosegregate with Cre1 and Cre3 resistance, together with flanking cDNA markers and other markers from homoeologous group 2 chromosomes, revealed a conserved gene order that suggests Cre1 and Cre3 are homeoloci.     

HKT1;5-like cation transporters linked to Na+ exclusion loci in wheat, Nax2 and Kna1

Bread wheat (Triticum aestivum) has a greater ability to exclude Na⁺ from its leaves and is more salt tolerant than durum wheat (Triticum turgidum L. subsp. durum [Desf.]). A novel durum wheat, Line 149, was found to contain a major gene for Na⁺ exclusion, Nax2, which removes Na⁺ from the xylem in the roots and leads to a high K⁺-to-Na⁺ ratio in the leaves. Nax2 was mapped to the distal region on chromosome 5AL based on linkage to microsatellite markers. The Nax2 locus on 5AL coincides with the locus for a putative Na⁺ transporter, HKT1;5 (HKT8). The Nax2 region on 5AL is homoeologous to the region on chromosome 4DL containing the major Na⁺ exclusion locus in bread wheat, Kna1. A gene member of the HKT1;5 family colocates to the deletion bin containing Kna1 on chromosome 4DL. This work provides evidence that Nax2 and Kna1 are strongly associated with HKT1;5 genes.     

Variants in the interleukin-1 alpha and beta genes,and the risk for periodontal disease in dogs

Elevated levels of interleukin-1 (IL-1) have been shown to amplify the inflammatory response against periodontopathogenic bacteria. In humans, polymorphisms in the IL1A and IL1B genes are the most well-studied genetic polymorphisms associated with periodontal disease (PD). In contrast to human, there is a lack of knowledge on the genetic basis of canine PD. A case–control study was conducted in which a molecular analysis of dog IL1A and IL1B genes was performed. Of the eight genetic variants identified, seven in IL1A gene and one in IL1B gene, IL1A/1_g.388A >C and IL1A/1_g.521T >A showed statistically significant differences between groups (adjusted OR (95% CI): 0.15 (0.03–0.76), P= 0.022; 5.76 (1.03–32.1), P= 0.046, respectively). It suggests that in the studied population the IL1A/1_g.388C allele is associated with a decreased PD risk, whereas the IL1A/1_g.521A allele can confer an increased risk. Additionally, the IL1A/2_g.515G >T variation resulted in a change of amino acid, i.e. glycine to valine. In silico analysis suggests that this change can alter protein structure and function, predicting it to be deleterious or damaging. This work suggests that IL1 genetic variants may be important in PD susceptibility in canines.