An ELMO2-RhoG-ILK network modulates microtubule dynamics

ELMO2 belongs to a family of scaffold proteins involved in phagocytosis and cell motility. ELMO2 can simultaneously bind integrin-linked kinase (ILK) and RhoG, forming tripartite ERI complexes. These complexes are involved in promoting β1 integrin-dependent directional migration in undifferentiated epidermal keratinocytes. ELMO2 and ILK have also separately been implicated in microtubule regulation at integrin-containing focal adhesions. During differentiation, epidermal keratinocytes cease to express integrins, but ERI complexes persist. Here we show an integrin-independent role of ERI complexes in modulation of microtubule dynamics in differentiated keratinocytes. Depletion of ERI complexes by inactivating the Ilk gene in these cells reduces microtubule growth and increases the frequency of catastrophe. Reciprocally, exogenous expression of ELMO2 or RhoG stabilizes microtubules, but only if ILK is also present. Mechanistically, activation of Rac1 downstream from ERI complexes mediates their effects on microtubule stability. In this pathway, Rac1 serves as a hub to modulate microtubule dynamics through two different routes: 1) phosphorylation and inactivation of the microtubule-destabilizing protein stathmin and 2) phosphorylation and inactivation of GSK-3β, which leads to the activation of CRMP2, promoting microtubule growth. At the cellular level, the absence of ERI species impairs Ca2+-mediated formation of adherens junctions, critical to maintaining mechanical integrity in the epidermis. Our findings support a key role for ERI species in integrin-independent stabilization of the microtubule network in differentiated keratinocytes

Aberrant Cx43 expression and mislocalization in metastatic human melanomas

At present, it is unclear if melanocytes contain Cx43 gap junctions and whether Cx43 expression is regulated in melanoma onset and progression. To this end, we cultured pure populations of mouse melanocytes and found that they had no detectable Cx43 and exhibited an inability for dye transfer indicating they were devoid of functional gap junctions. Given the evidence that melanomas acquire the expression of other connexin isoforms during tumor progression, we assessed if Cx43 was also expressed and assembled into gap junctions at any stage of human melanoma onset and progression to distant metastases. Nearly all primary melanomas within the epidermis lacked Cx43. In contrast, nodal metastases expressed low levels of Cx43 which was markedly higher in distant metastases that had invaded vital organs. Importantly, in all stages of melanoma progression, Cx43 could be detected in intracellular compartments but was rarely assembled into gap junctions indicative of functional gap junction channels. Overall, these studies suggest that melanocytes do not form Cx43 homocellular gap junctions and even though Cx43 levels increase during melanoma progression, this connexin rarely assembles into gap junction structures

Relationships between phenotypic plasticity and environmental variables.

To understand the relations between environment and phenotypic plasticity is important to forecast any possible adaptation of plants to climate change. We tested for any difference between central and marginal (Mediterranean and Alpine). Study was performed on 20 populations chosen on the basis of their distance from niche optimum.In Mediterranean marginal populations : \u2022 wide flowers display corolla, \u2022 short stamen, inducing more investment in attractiveness than in seed maturation \u2022 lower pollen production and seed set. Our results suggestthat: Largest floral display and lowest allocation of resources for seeds production in Mediterranean populations may be due to the highest competition for resources (pollinators, water and soil nutrient) together with the lowest resource availability. Future climate change will probably bring about: extinction of low altitudes populations the upward shift of other

Management of an invasive plant in a Mediterranean Protected Area: the experience of Senecio deltoideus in Italy

Biological invasions are one of the most serious threats to global biodiversity and ecosystem integrity. The problem is growing year by year and a large number of protected areas worldwide are today invaded by at least one exotic species. In this study, we tested the eco-friendly and cost-effective weeding control of Senecio deltoideus in a Regional Protected Area in the North Mediterranean region. During a two years experiment, four techniques compatible with the local laws on protected areas (natural-herbicide, flame-weeding, mulching and mowing) were applied five times a season on sixty plots, compared with fifteen untreated controls. All techniques were effective in reducing Senecio covering: after the first year the maximum covering was limited to 37.93% (flame weeding) with a mean value of 10%; after second year the covering was further reduced (17.02% max; 2% mean). Interestingly, during the second year all plots submitted to a one-year treatment showed an enduring control of S. deltoideus covering (40.73% max; 20% mean). Taking into account feasibility and their impact on the environment, the weeding control recommendable for S. deltoideus is mowing. In a long-time management strategy, the selected treatment could be applied every two years with a drastic reduction in costs for the manager of the protected area

Reproductive traits of the invasive species Acacia dealbata Link. in the northern Mediterranean basin

Among the many exotic plants introduced in the last two centuries in Northern Mediterranean Basin Acacia dealbata Link. is one of the most invasive. Despite its presence in the region since many years, it has not yet been investigated how the species has established itself and has formed small forests. In this study, we aimed to gather data on reproductive trait of the invasive species A. dealbata at the northern limit of the Mediterranean bioclimatic region. In six naturalized populations, fruit and seed set were estimated and seed germination was tested in laboratory. Two out of the six populations failed to set fruits, and the fruit set was always low as observed in other invaded areas of the world. Only three populations produced germinating seeds whose rates were comparable to other invasive areas. The seeds may constitute a long-lasting seed bank that may favour the colonization of the species in areas disturbed by external factors. In conclusion, the reproductive system may contributes only partially to the spread and invasiveness of the species in the Northern Mediterranean basin, while the plant to spread itself adopts also other vegetative strategies