September 22, 2019  |  

Order of removal of conventional and nonconventional introns from nuclear transcripts of Euglena gracilis.

Nuclear genes of euglenids and marine diplonemids harbor atypical, nonconventional introns which are not observed in the genomes of other eukaryotes. Nonconventional introns do not have the conserved borders characteristic for spliceosomal introns or the sequence complementary to U1 snRNA at the 5′ end. They form a stable secondary structure bringing together both exon/intron junctions, nevertheless, this conformation does not resemble the form of self-splicing or tRNA introns. In the genes studied so far, frequent nonconventional introns insertions at new positions have been observed, whereas conventional introns have been either found at the conserved positions, or simply lost. In this work, we examined the order of intron removal from Euglena gracilis transcripts of the tubA and gapC genes, which contain two types of introns: nonconventional and spliceosomal. The relative order of intron excision was compared for pairs of introns belonging to different types. Furthermore, intermediate products of splicing were analyzed using the PacBio Next Generation Sequencing system. The analysis led to the main conclusion that nonconventional introns are removed in a rapid way but later than spliceosomal introns. Moreover, the observed accumulation of transcripts with conventional introns removed and nonconventional present may suggest the existence of a time gap between the two types of splicing.

July 19, 2019  |  

Bats may eat diurnal flies that rest on wind turbines

Bats are currently killed in large numbers at wind turbines worldwide, but the ultimate reason why this happens remains poorly understood. One hypothesis is that bats visit wind turbines to feed on insects exposed at the turbine towers. We used single molecule next generation DNA sequencing to identify stomach contents of 18 bats of four species (Pipistrellus pygmaeus, Nyctalus noctula, Eptesicus nilssonii and Vespertilio murinus) found dead under wind turbines in southern Sweden. Stomach contents were diverse but included typically diurnal flies, e.g. blow-flies (Calliphoridae), flesh-flies (Sarcophagidae) and houseflies (Muscidae) and also several flightless taxa. Such prey items were eaten by all bat species and at all wind turbine localities and it seems possible that they had been captured at or near the surface of the turbines at night. Using sticky traps, we documented an abundance of swarming (diurnal) ants (Myrmica spp.) and sometimes blow-flies and houseflies at the nacelle house. Near the base of the tower the catches were more diverse and corresponded better with the taxa found in the bat stomachs, including various diurnal flies. To evaluate if flies and other insects resting on the surface of a wind turbine are available to bats, we ensonified a house fly (Musca) on a smooth (plastic) surface with synthetic ultrasonic pulses of the frequencies used by the bat species that we had sampled. The experiment revealed potentially useful echoes, provided the attack angle was low and the frequency high (50–75 kHz). Hence resting flies and other arthropods can probably be detected by echolocating bats on the surface of a wind turbine. Our findings are consistent with published observations of the behavior of bats at wind turbines and may actually explain the function of some of these behaviors.

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