Conservation Genetics of Kangaroo Mice, Genus Microdipodops

The two currently recognized species of kangaroo mice, Microdipodops megacephalus and M. pallidus, inhabit sandy soils of the Great Basin Desert in western North America. Given their habitat specificity and the fluctuating climate throughout the Pleistocene, kangaroo mice likely endured a turbulent biogeographic history that resulted in disjunct distributions and isolation of genetic lineages. Recent phylogenetic investigations using mitochondrial data have revealed several mitochondrial clades within this genus that may represent cryptic species. These mitochondrial clades are genetically unique, occupy relatively small distributions, and, as such, may be at an increased risk of extinction due to climate change and extensive recent habitat alteration. Herein, we apply haplotype network, population genetic, and historical demographic analyses to mitochondrial data of each Micropdipodops species and mitochondrial clade to assess conservation genetics within kangaroo mice. Results indicate that each mitochondrial clade is a distinct lineage with little to no gene flow occurring among clades. Additionally, historical demographic analyses support past population expansions and identify locations of past refugium for each distinct lineage. Although mitochondrial data indicate that the clades appear to be in approximate genetic equilibrium and have not suffered any extreme bottlenecks over time, there is still concern for the survival of smaller and more vulnerable Microdipodops subpopulations due to impending habitat threats in the Great Basin Desert.     

Transposon tagging in diploid strawberry

Fragaria vesca was transformed with a transposon tagging construct harbouring amino terminally deleted maize transposase and EGFP (Ac element), NPTII, CaMV 35S promoter (P35S) driving transposase and mannopine synthase promoter (Pmas) driving EGFP (Ds element). Of 180 primary transgenics, 48 were potential launch pads, 72 were multiple insertions or chimaeras, and 60 exhibited somatic transposition. T(1) progeny of 32 putative launch pads were screened by multiplex PCR for transposition. Evidence of germ-line transposition occurred in 13 putative launch pads; however, the transposition frequency was too low in three for efficient recovery of transposants. The transposition frequency in the remaining launch pads ranged from 16% to 40%. After self-pollination of the T(0) launch pads, putative transposants in the T(1) generation were identified by multiplex PCR. Sequencing of hiTAIL-PCR products derived from nested primers within the Ds end sequences (either P35S at the left border or the inverted repeat at the right border) of T(1) plants revealed transposition of the Ds element to distant sites in the strawberry genome. From more than 2400 T(1) plants screened, 103 unique transposants have been identified, among which 17 were somatic transpositions observed in the T(0) generation. Ds insertion sites were dispersed among various gene elements [exons (15%), introns (23%), promoters (30%), 3' UTRs (17%) as well as intergenically (15%)]. Three-primer (one on either side of the Ds insertion and one within the Ds T-DNA) PCR could be used to identify homozygous T(2) transposon-tagged plants. The mutant collection has been catalogued in an on-line database.     

Photooxidative reactions in chloroplast thylakoids. Evidence for a Fenton-type reaction promoted by superoxide or ascorbate

A methyl viologen (MV)^* mediated Mehler reaction was studied using Type C and D chloroplasts (thylakoids) from spinach. The extent of photooxidative reactions were measured as (a) rate of ethylene formation from methional oxidation indicating the production of oxygen radicals, and (b) rate of malondialdehyde (MDA) formation as a measure of lipid peroxidation. Without added ascorbate, 1 M FerricEDTA increased ethylene formation by greater than 4-fold, but had no effect on MDA production. Ascorbate (1 mM) produced a tripling of ethylene while it reduced MDA formation in the presence of iron. Radical scavengers diethyldithiocarbamate (DDTC), formate, 1,4-diazabicyclo (2.2.2octane) (DABCO), inhibited ethylene formation. Using 0,4 M mannitol to scavenge hydroxyl radicals, the rates of ethylene formation were reduced 40 to 60% with or without 1 M Fe(III) EDTA. The strong oxidant(s) not scavenged by mannitol are hypothesized to be either alkoxyl radicals from lipid peroxidation, or site specific formation of hydroxyl radicals in a lipophillic environment not exposed to mannitol. Singlet oxygen does not appear to be a significant factor in this system. Catalase strongly inhibited both ethylene and MDA synthesis under all conditions; 1 mM ascorbate did not reverse this inhibition. However, the strong superoxide dismutase (SOD) inhibition of ethylene and MDA formation was completely reversed by 1 mM ascorbate. This suggests that superoxide was functioning as an iron reducing agent and that in its absence, ascorbate was similarly promoting oxidations. Therefore, these oxidative processes were dependent on the presence of H₂O₂ and a reducing agent, suggesting the involvement of a Fenton-type reaction.Abbreviation DABCO 1,4-diazabicyclo(2.2.2.octane) - DCMU 3-(3,4 Dichlorophenyl). 1,1-dimethyl urea - DDTC diethyldithiocarbamate - EDTA ethylenediamine-tetraacetic acid - MDA malondialdehyde - MV methyl viologen - SOD superoxide dismutase - TBA thiobarbituric acid - TCA trichloroacetic acid Scientific contribution number 1315 from the New Hampshire Agriculture Experiment Station.     

Cerapeplus gen.n. and the classification of micropeplids (Coleoptera: Micropeplidae)

Cerapeplus siamensis gen.n., sp.n. from Thailand is described and illustrated. The new genus is characterized by filament-based lamellar secretions arising from the lateral body margin, a feature observed for the first time in Coleoptera. Possible autapomorphies for the micropeplid genera are discussed. It is concluded that Cerapeplus and Kalissus are monophyletic; Micropeplus and/Or Peplomicrus are probably polyphyletic but both genera together form a monophyletic group. A number of characters support the family status of the micropeplids recently proposed by some authors. A revised family diagnosis is provided.