Heat-evolved microalgal symbionts increase coral bleaching tolerance.

Coral reefs worldwide are suffering mass mortalities from marine heat waves. With the aim of enhancing coral bleaching tolerance, we evolved 10 clonal strains of a common coral microalgal endosymbiont at elevated temperatures (31°C) for 4 years in the laboratory. All 10 heat-evolved strains had expanded their thermal tolerance in vitro following laboratory evolution. After reintroduction into coral host larvae, 3 of the 10 heat-evolved endosymbionts also increased the holobionts' bleaching tolerance. Although lower levels of secreted reactive oxygen species (ROS) accompanied thermal tolerance of the heat-evolved algae, reduced ROS secretion alone did not predict thermal tolerance in symbiosis. The more tolerant symbiosis exhibited additional higher constitutive expression of algal carbon fixation genes and coral heat tolerance genes. These findings demonstrate that coral stock with enhanced climate resilience can be developed through ex hospite laboratory evolution of their microalgal endosymbionts.

Genomic innovations, transcriptional plasticity and gene loss underlying the evolution and divergence of two highly polyphagous and invasive Helicoverpa pest species.

BACKGROUND: Helicoverpa armigera and Helicoverpa zea are major caterpillar pests of Old and New World agriculture, respectively. Both, particularly H. armigera, are extremely polyphagous, and H. armigera has developed resistance to many insecticides. Here we use comparative genomics, transcriptomics and resequencing to elucidate the genetic basis for their properties as pests. RESULTS: We find that, prior to their divergence about 1.5 Mya, the H. armigera/H. zea lineage had accumulated up to more than 100 more members of specific detoxification and digestion gene families and more than 100 extra gustatory receptor genes, compared to other lepidopterans with narrower host ranges. The two genomes remain very similar in gene content and order, but H. armigera is more polymorphic overall, and H. zea has lost several detoxification genes, as well as about 50 gustatory receptor genes. It also lacks certain genes and alleles conferring insecticide resistance found in H. armigera. Non-synonymous sites in the expanded gene families above are rapidly diverging, both between paralogues and between orthologues in the two species. Whole genome transcriptomic analyses of H. armigera larvae show widely divergent responses to different host plants, including responses among many of the duplicated detoxification and digestion genes. CONCLUSIONS: The extreme polyphagy of the two heliothines is associated with extensive amplification and neofunctionalisation of genes involved in host finding and use, coupled with versatile transcriptional responses on different hosts. H. armigera's invasion of the Americas in recent years means that hybridisation could generate populations that are both locally adapted and insecticide resistant.

Modulation of intracortical excitability in human hand motor areas. The effect of cutaneous stimulation and its topographical arrangement.

Changes in afferent input can alter the excitability of intracortical inhibitory systems. For example, using paired transcranial magnetic stimulation (TMS), both electrical digital stimulation and muscle vibration have been shown to reduce short-interval intracortical inhibition (SICI). The effects following muscle vibration are confined to the corticospinal projection to the vibrated muscles. The results following digital stimulation are less clear and the relative timing of the cutaneous stimulation and TMS is critical. Here we investigated further whether changes in SICI following digit stimulation exhibit topographic specificity. Eleven normal subjects were investigated (age 28.2+/-7.5 years, mean+/-SD). Electromyographic recordings were made from the right first dorsal interosseous (FDI), abductor digiti minimi (ADM) and abductor pollicis brevis (APB) muscles. SICI was measured, with and without preceding electrical digit II or digit V cutaneous stimulation. The interval between the digital nerve stimulus and test magnetic stimulus was independently set for each subject and established by subtracting the onset latency of the motor evoked potential (MEP) from the latency of the E2 component of the cutaneomuscular reflex. Therefore, measures of intracortical excitability were made at a time at which it is known that cutaneous input is capable of modulating cortical excitability. Single digital nerve stimuli applied to digit II significantly reduced SICI in FDI but not in ADM. Single digital nerve stimuli applied to digit V significantly reduced SICI in ADM but not in FDI or APB. There was a more generalised effect on intracortical facilitation (ICF) with both digit II and digit V stimulation significantly increasing ICF in FDI and ADM. Digital stimulation (either DII or DV) did not significantly affect SICI/ICF in APB. These findings show that appropriately timed cutaneous stimuli are capable of modulating SICI in a topographically specific manner. We suggest that the selective decrease in SICI seen with cutaneous stimulation may be important for focusing of muscle activation during motor tasks.