Biology of <Emphasis Type="Italic">Lasioglossum</Emphasis> (<Emphasis Type="Italic">L.</Emphasis>) <Emphasis Type="Italic">majus</Emphasis> (Hymenoptera: Halictidae), a largely solitary sweat bee with behavioural adaptations to communality

Within the bee family Halictidae there have been three origins of sociality. Although detection of origins and reversal from sociality requires phylogenetic studies, at a behavioural level a predisposition to sociality can be detected by analysis of intra-specific interactions. We studied aspects of nesting biology and behavioural interactions in Lasioglossum (Lasioglossum) majus, a poorly known halictine inhabiting temperate regions of Europe, which is suspected to be solitary. Nests were found to be largely used by one female, but some were shared by more than one individual. These few nests, whose entrances were very close to each other, were found to be connected underground. A few individuals were observed to enter in a nest where a female was waiting, behaving as a guard and allowing the incoming bee to enter the nest. By use of circle-tube experiments, the behavioural repertoire exhibited by females during encounters was assessed. Levels of withdrawal and cooperative events were comparable with those observed in other solitary nesting species, but aggressive events were very rare, as in several observed communal species. We conclude that L. (L.) majus females, despite general solitary nesting, possess behavioural components enabling them to adopt, probably in high nest-density areas, nest-sharing strategies. A similar kind of local social polymorphism has been observed in two other species of the subgenus Lasioglossum, but these are the first data available on a European species and the first record of subterranean connections among nests of halictid bees.     

Philopatry, nest choice, and aggregation temporal–spatial change in the digger wasp Cerceris arenaria (Hymenoptera: Crabronidae)

Studying temporal and spatial changes of aggregations of digger wasps through nesting seasons is interesting because of its link to social evolution via a semi-social pathway, but information about this topic is scarce. An aggregation of Cerceris arenaria Latreille was studied during 1997–1999 and for a short period in 2001. The colony grew in area and number of nests through the first three seasons, but the aggregation reduced in 2001, and this decrease was confirmed by a count of nests made in 2003 and 2005. The positions of the nest entrances remained almost constant over the years, at least in high-nest-density areas, because of the repeated use of the same burrows from which they emerged. This fact permits the population to exploit for many years a restricted area and could act as a nest-density-regulation method for fossorial species that rarely dig new nests, preventing an excessive nest density. The newly emerged females did not dig new nests, showed a high philopatry in the choice of their first nest, and preferred to look for other nests to occupy close to the ones recently abandoned (mainly for an undergone usurpation by a conspecific female). Philopatry, along with lack of new nest digging and position-dependent nest choice, is probably an important factor maintaining spatial stability of the aggregation through the years and could represent a first step in the evolution of a higher sociality in apoid burrowing Hymenoptera.     

Nesting habits of two spider wasps: Anoplius infuscatus and Episyron sp. (Hymenoptera: Pompilidae), with a review of the literature

Many behavioural aspects of Anoplius infuscatus (Vander Linden) and Episyron sp. Schioedte were examined in detail, both on a qualitative and, when possible, on a quantitative level, during a long-term field study in Northern Italy. Both wasps dig unicellular nests on bare soil, which are filled with a single spider to feed the brood. The main differences regard the way to hunt their prey, that of burrowing, that of transporting and introducing the spider into the nest, the habit of amputating spider legs and the abdominal movements during nest closing. On the whole, starting from prey capture to nest closure, A. infuscatus is significantly slower than Episyron. The observed ethological differences are well fitted to the exploitation of the different preys consisting in wolf spiders (Lycosidae) and orb weaving spiders (Araneidae), respectively. Some flexibility in the observed behaviour is described. A critical re-examination of the literature shows that, even if most results agree with those of previous authors, two controversial points remain open regarding Episyron species: the position of the egg (on the prey or on the cell wall) and the way to grasp the spider during tranport and introdution into the nest.     

Genetic dissection of Al tolerance QTLs in the maize genome by high density SNP scan

Background

Aluminum (Al) toxicity is an important limitation to food security in tropical and subtropical regions. High Al saturation on acid soils limits root development, reducing water and nutrient uptake. In addition to naturally occurring acid soils, agricultural practices may decrease soil pH, leading to yield losses due to Al toxicity. Elucidating the genetic and molecular mechanisms underlying maize Al tolerance is expected to accelerate the development of Al-tolerant cultivars.

Results

Five genomic regions were significantly associated with Al tolerance, using 54,455 SNP markers in a recombinant inbred line population derived from Cateto Al237. Candidate genes co-localized with Al tolerance QTLs were further investigated. Near-isogenic lines (NILs) developed for ZmMATE2 were as Al-sensitive as the recurrent line, indicating that this candidate gene was not responsible for the Al tolerance QTL on chromosome 5, qALT5. However, ZmNrat1, a maize homolog to OsNrat1, which encodes an Al³⁺ specific transporter previously implicated in rice Al tolerance, was mapped at ~40 Mbp from qALT5. We demonstrate for the first time that ZmNrat1 is preferentially expressed in maize root tips and is up-regulated by Al, similarly to OsNrat1 in rice, suggesting a role of this gene in maize Al tolerance. The strongest-effect QTL was mapped on chromosome 6 (qALT6), within a 0.5 Mbp region where three copies of the Al tolerance gene, ZmMATE1, were found in tandem configuration. qALT6 was shown to increase Al tolerance in maize; the qALT6-NILs carrying three copies of ZmMATE1 exhibited a two-fold increase in Al tolerance, and higher expression of ZmMATE1 compared to the Al sensitive recurrent parent. Interestingly, a new source of Al tolerance via ZmMATE1 was identified in a Brazilian elite line that showed high expression of ZmMATE1 but carries a single copy of ZmMATE1.

Conclusions

High ZmMATE1 expression, controlled either by three copies of the target gene or by an unknown molecular mechanism, is responsible for Al tolerance mediated by qALT6. As Al tolerant alleles at qALT6 are rare in maize, marker-assisted introgression of this QTL is an important strategy to improve maize adaptation to acid soils worldwide.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-153) contains supplementary material, which is available to authorized users.     

Alteration of the Glucagon Axis in GPR120 (FFAR4) Knockout Mice: A ROLE FOR GPR120 IN GLUCAGON SECRETION

GPR40 (FFAR1) and GPR120 (FFAR4) are G-protein-coupled receptors (GPCRs) that are activated by long chain fatty acids (LCFAs). GPR40 is expressed at high levels in islets and mediates the ability of LCFAs to potentiate glucose-stimulated insulin secretion (GSIS). GPR120 is expressed at high levels in colon, adipose, and pituitary, and at more modest levels in pancreatic islets. The role of GPR120 in islets has not been explored extensively. Here, we confirm that saturated (e.g. palmitic acid) and unsaturated (e.g. docosahexaenoic acid (DHA)) LCFAs engage GPR120 and demonstrate that palmitate- and DHA-potentiated glucagon secretion are greatly reduced in isolated GPR120 KO islets. Remarkably, LCFA potentiated glucagon secretion is similarly reduced in GPR40 KO islets. Compensatory changes in mRNA expression of GPR120 in GPR40 KO islets, and vice versa, do not explain that LCFA potentiated glucagon secretion seemingly involves both receptors. LCFA-potentiated GSIS remains intact in GPR120 KO islets. Consistent with previous reports, GPR120 KO mice are hyperglycemic and glucose intolerant; however, our KO mice display evidence of a hyperactive counter-regulatory response rather than insulin resistance during insulin tolerance tests. An arginine stimulation test and a glucagon challenge confirmed both increases in glucagon secretion and liver glucagon sensitivity in GPR120 KO mice relative to WT mice. Our findings demonstrate that GPR120 is a nutrient sensor that is activated endogenously by both saturated and unsaturated long chain fatty acids and that an altered glucagon axis likely contributes to the impaired glucose homeostasis observed in GPR120 KO mice.