Cryptic N2 Fixation
- Caroline Ash
Lichen-covered buildings, rocks, and trees are a common sight. Indeed, if they remain static for long enough, or simply grow slowly, most objects on Earth's surface become coated by cyanobacteria, algae, fungi, lichens, and bryophytes. These coatings are called cryptogamic covers, and Elbert et al. estimate that these photoautotrophic communities make substantial contributions to carbon and nitrogen cycling. Carbon uptake by these communities was estimated to be highest in Europe (at about 10% of net primary production) and lowest in Africa (at about 4%) and in total to constitute about 1% of the carbon content of terrestrial vegetation. Far more striking is their relative contribution to total biological nitrogen fixation, ranging from 30% in Europe and South America to more than 80% in Asia and North America. This means that models of nitrogen cycling need to account for the activities of cryptogamic covers, or they may miss the majority of biological nitrogen fixation occurring in some regions.
Nat. Geosci. 5, 459 (2012).
- Cell Signaling
Toll-Like Receptor Tag Team
- L. Bryan Ray
How many receptors does it take to initiate an antiviral response? Yamashita et al. say it's two, plus an additional tyrosine kinase. First, you need Toll-like Receptor 3 (TLR3), which has a well-characterized role in the detection of double-stranded RNA (dsRNA) and initiation of protective cellular responses. Earlier findings showed that TLR3 differs from other TLRs in requiring phosphorylation of two tyrosine residues in its cytoplasmic tail for activation. Here, another receptor is implicated in the activation of antiviral responses by TLR3—the epidermal growth factor receptor (EGFR), which is itself a tyrosine kinase. The EGFR was found to associate with dsRNA-activated TLR3 in endosomal membranes along with another tyrosine kinase, Src. Both EGFR and Src appeared to phosphorylate a particular tyrosine residue in TLR3, and inhibition of the kinases inhibited TLR3-dependent antiviral responses. Thus, antiviral responses may involve interactions between signaling systems controlling cell growth and those mediating innate immune responses.
Sci. Signal. 5, ra50 (2012).
A Wealth of Meaning
- Gilbert Chin
The United Nations recently reported that women spend anywhere from twice to four times the number of hours on family and domestic responsibilities as men, which has invigorated a discussion about the tradeoffs between career and family that women often face. Kushlev et al. examined the link between wealth—in the form of education and income—and subjective measures of the meaningfulness of life and happiness of residents of British Columbia. An inverse relation was observed between socioeconomic status and the meaningfulness of life for parents when taking care of their children, whereas during the rest of the day, there was no such correlation. In a follow-up field experiment, the concept of wealth was casually introduced while asking attendees at a children's festival about their happiness and sense of meaning. Once again, there was no link between wealth and happiness, but a negative relation between thoughts of wealth and a sense of meaningfulness. Thus, paradoxically, affluence may compromise one of the subjective benefits of parenting—a sense of meaning in life.
J. Exp. Soc. Psychol. 48, 10.1016/j.jesp.2012.06.001 (2012).
- Ocean Science
Refuges for Corals
- H. Jesse Smith
Global warming presents a real and present danger to coral reefs, owing to the increasing frequency of bleaching events as water temperatures rise. In the central Pacific, for instance, sea surface temperatures are projected to increase by nearly 3°C by the end of this century, a rise that could be devastating to many of the rich marine ecosystems that thrive there. However, the climate system is complex and heterogeneous in its response to global warming, particularly at smaller scales, and there should be regions in which surface ocean warming is less pronounced than others. Karnauskas and Cohen report that warming around some Pacific islands could be mitigated by enhanced upwelling caused by the strengthening of the equatorial undercurrent, which models predict will occur. Less warming should translate into less severe negative impacts on the coral reefs and rich ecosystems in those locations, potentially providing vital refuges in otherwise more hostile environmental conditions. Although few coral reefs may benefit from this island effect, because the equatorial undercurrent flows only around the Equator, knowing where refuges could exist might help planning efforts to protect them in ways that we can control.
Nat. Clim. Change 2, 530 (2012).