Mate recognition in the South African citrus thrips Scirtothrips aurantii (Faure) and cross-mating tests with populations from Australia and South Africa

South African citrus thrips (Scirtothrips aurantii) is a pest of citrus, mango and other horticultural species in its native range, which encompasses a large part of Africa. Its adventitious establishment in Australia in 2002 was a major cause for concern. The thrips, 11 years after its incursion into Australia, has remained on plants of a single host plant genus Bryophyllum (Crassulaceae). Characterization of the Specific-Mate Recognition System of the Bryophyllum population of thrips present in Australia and behavioral bioassay experiments revealed that compounds found in the insects' body extracts play a crucial role in mate recognition of S. aurantii. Reciprocal cross-mating experiments between the Australian Bryophyllum insects and South African S. aurantii from horticultural host plants showed that mating frequencies were significantly lower in test crosses (Bryophyllum x horticultural) than in controls (Bryophyllum x Bryophyllum or horticultural x horticultural), which indicates there are at least two distinct species within S. aurantii and suggests further tests of this interpretation. The results suggest that these tiny phytophagous insects localize mates through their association with a particular host plant species (or closely-related group of species). Also, specific tests are suggested for clarifying the species status of the host-associated populations of S. aurantii in Africa

Migration through a small pore disrupts inactive chromatin organization in neutrophil-like cells

Abstract Background Mammalian cells are flexible and can rapidly change shape when they contract, adhere, or migrate. The nucleus must be stiff enough to withstand cytoskeletal forces, but flexible enough to remodel as the cell changes shape. This is particularly important for cells migrating through confined spaces, where the nuclear shape must change in order to fit through a constriction. This occurs many times in the life cycle of a neutrophil, which must protect its chromatin from damage and disruption associated with migration. Here we characterized the effects of constricted migration in neutrophil-like cells. Results Total RNA sequencing identified that migration of neutrophil-like cells through 5- or 14-μm pores was associated with changes in the transcript levels of inflammation and chemotaxis-related genes when compared to unmigrated cells. Differentially expressed transcripts specific to migration with constriction were enriched for groups of genes associated with cytoskeletal remodeling. Hi-C was used to capture the genome organization in control and migrated cells. Limited switching was observed between the active (A) and inactive (B) compartments after migration. However, global depletion of short-range contacts was observed following migration with constriction compared to migration without constriction. Regions with disrupted contacts, TADs, and compartments were enriched for inactive chromatin. Conclusion Short-range genome organization is preferentially altered in inactive chromatin, possibly protecting transcriptionally active contacts from the disruptive effects of migration with constriction. This is consistent with current hypotheses implicating heterochromatin as the mechanoresponsive form of chromatin. Further investigation concerning the contribution of heterochromatin to stiffness, flexibility, and protection of nuclear function will be important for understanding cell migration in relation to human health and disease