Sixteen new simple sequence repeat markers from Brassica juncea expressed sequences and their cross‐species amplification

The availability of expressed sequence data derived from gene discovery programs enables mining for simple sequence repeats (SSR), providing useful genetic markers for crop improvement. These markers are inexpensive, require minimal labour to produce and can frequently be associated with functionally annotated genes. This study presents the development and characterization of 16 expressed sequence tags (EST)‐SSR markers from Brassica juncea and their cross‐amplification across Brassica species. Sixteen primer pairs were assessed for polymorphism in all genomes of the diploid and amphidiploid Brassica species. The markers show reliable amplification, considerable polymorphism and high transferability across species, demonstrating the utility of EST‐SSRs for genetic analysis of brassicas.     

Identification and characterization of simple sequence repeat markers from Brassica napus expressed sequences

The availability of expressed sequence data derived from gene discovery programs enables mining for simple sequence repeats (SSR), providing useful genetic markers for crop improvement. These markers are inexpensive, require minimal labour to produce and can frequently be associated with functionally annotated genes. This study presents the development and characterization of 24 expressed sequence tags (EST)‐SSR markers from Brassica napus and their cross‐amplification across Brassica species. The markers show reliable amplification, genome specificity and considerable polymorphism, demonstrating the utility of EST‐SSRs for genetic analysis of wild Brassica populations and commercial Brassica germplasm.     

Influence of colony associated factors on nest selection in an Indian queenless ant

1. Organisms face the difficult task of selecting an optimal new nest from the available options during relocation. Studies on honeybees and ants in their natural habitat indicate that scouts encounter multiple options that vary in their physical and biotic characteristics. 2. Architectural features, location, odour, and the presence of nest mates impact their choice of nest site selection. In order to examine the influence of diverse parameters on final nest site selection we conducted choice experiments on ants in the context of relocation. 3. After controlling for any influence by physical characteristics, we found that the presence of brood, adults, and colony odour acted as attractants with more colonies relocating into these new nests than expected by chance alone. In contrast, the presence of a reproductive female, or familiarity of location had no influence on the choice. New nests containing dead ants evoked cleaning responses from scouts, which may interfere with relocation into these nests. 4. Even although colonies consist of hundreds of adults and brood, colony integrity was maintained in 98.7% of colonies. Furthermore, we found that none of the eight studied colonies relocated when faced with minor flooding in their natural habitat, indicating that the cost of relocation is non‐trivial and that this species is capable of minor damage repairs. 5. These observations highlight the complexity of relocation in general, allow the characterisation of desirable nest attributes in this species, and highlight the need for similar exploration in other social insects.     

RGK regulation of voltage-gated calcium channels

Voltage-gated calcium channels(VGCCs) play critical roles in cardiac and skeletal muscle contractions,hormone and neurotransmitter release,as well as slower processes such as cell proliferation,differentiation,migration and death.Mutations in VGCCs lead to numerous cardiac,muscle and neurological disease,and their physiological function is tightly regulated by kinases,phosphatases,G-proteins,calmodulin and many other proteins.Fifteen years ago,RGK proteins were discovered as the most potent endogenous regulators of VGCCs.They are a family of monomeric GTPases(Rad,Rem,Rem2,and Gem/Kir),in the superfamily of Ras GTPases,and they have two known functions: regulation of cytoskeletal dynamics including dendritic arborization and inhibition of VGCCs.Here we review the mechanisms and molecular determinants of RGK-mediated VGCC inhibition,the physiological impact of this inhibition,and recent evidence linking the two known RGK functions.     

A New Laboratory Technique for Studying the Effects of Heavy Metals on Bryophyte Growth

A novel, non-destructive method for measuring moss gametophytegrowth rates is presented. Standard 2-cm moss gametophores aresupported vertically on Velcro strips held within a clear perspexbox, with their bases resting in liquid. Shoots sampled fromthe field were either continuously exposed to test solutionsvia their cut bases, or by preliminary pulse-immersion. Growthwas assessed by linear extension, or final dry mass, and showeddifferent patterns and sensitivities to heavy metals using thetwo exposure methods. A biologically appropriate assessmentof toxicity was established, using tissue concentrations comparableto material from polluted field sites, by considering the cellularlocation of heavy metals in shoots. A linear relationship wasestablished between apical growth and intracellular Zn concentrationrecovered in the newly produced gametophyte tissue, irrespectiveof the method of exposure or Zn concentration in the remainingor original shoot portion. The limitations and ambiguity associatedwith many heavy-metal monitoring and toxicity studies are addressed,and the advantages and further applications offered by thisgrowth system are discussed. Rhytidiadelphus squarrosus ; growth; heavy metal effects; cadmium; copper; lead; zinc; bioassay     

Maternal <Emphasis Type="Italic">MTHFR</Emphasis> polymorphism (677 C–T) and risk of Down’s syndrome child: meta-analysis

Methylenetetrahydrofolate reductase (MTHFR) is the most important gene that participates in folate metabolism. Presence of valine instead of alanine at position 677 and elevated levels of homocystein causes DNA hypomethylation which in turn favours nondisjunction. In this study, we conducted a meta-analysis to establish link between maternal single-nucleotide polymorphism (SNP) and birth of Down’s syndrome (DS) child. A total of 37 case–control studies were selected for analysis including our own, in which we investigated 110 cases and 111 control mothers. Overall, the result of meta-analysis showed significant risk of DS affected by the presence of maternal SNP (MTHFR 677 C–T OR = 0.816, 95% CI = 0.741–0.900, P<0.0001). Heterogeneity of high magnitude was observed among the studies. The chi-square value suggested a highly significant association between homozygous mutant TT genotype and birth of DS child (χ²=23.63, P=0.000). Genetic models suggested that ‘T’ allele possesses high risk for DS whether present in dominant (OR = 1.23, 95% CI = 1.13–1.34); codominant (OR = 1.17, 95% CI = 1.10–1.25) or recessive (OR = 1.21, 95% CI = 1.05–1.38) form. The analysis from all 37 studies combined together suggested that MTHFR 677 C–T is a major risk factor for DS birth.     

Mapping of stripe rust resistance gene in an <Emphasis Type="Italic">Aegilops caudata</Emphasis> introgression line in wheat and its genetic association with leaf rust resistance

A pair of stripe rust and leaf rust resistance genes was introgressed from Aegilops caudata, a nonprogenitor diploid species with the CC genome, to cultivated wheat. Inheritance and genetic mapping of stripe rust resistance gene in backcross-recombinant inbred line (BC-RIL) population derived from the cross of a wheat–Ae. caudata introgression line (IL) T291-2(pau16060) with wheat cv. PBW343 is reported here. Segregation of BC-RILs for stripe rust resistance depicted a single major gene conditioning adult plant resistance (APR) with stripe rust reaction varying from TR-20MS in resistant RILs signifying the presence of some minor genes as well. Genetic association with leaf rust resistance revealed that two genes are located at a recombination distance of 13%. IL T291-2 had earlier been reported to carry introgressions on wheat chromosomes 2D, 3D, 4D, 5D, 6D and 7D. Genetic mapping indicated the introgression of stripe rust resistance gene on wheat chromosome 5DS in the region carrying leaf rust resistance gene LrAc, but as an independent introgression. Simple sequence repeat (SSR) and sequence-tagged site (STS) markers designed from the survey sequence data of 5DS enriched the target region harbouring stripe and leaf rust resistance genes. Stripe rust resistance locus, temporarily designated as YrAc, mapped at the distal most end of 5DS linked with a group of four colocated SSRs and two resistance gene analogue (RGA)-STS markers at a distance of 5.3 cM. LrAc mapped at a distance of 9.0 cM from the YrAc and at 2.8 cM from RGA-STS marker Ta5DS_2737450, YrAc and LrAc appear to be the candidate genes for marker-assisted enrichment of the wheat gene pool for rust resistance.