In Science this week, a team led by researchers from the University of Wisconsin uncovered the reasons why one variant of soybeans is particularly resistant to soybean cyst nematode, the most economically damaging pathogen for the soybean industry. Among different soybean varieties, the one with the Rhg1, or resistance to H. glycines, quantitative trait locus on chromosome 18 "consistently contributes much more effective SCN resistance than any other known loci." To determine the molecular basis for this resistance, the investigators used RNAi to silence Rhg1-associated genes and found that a cluster of them work together to provide the nematode resistance. Further, whole-genome shotgun sequencing revealed that plants carrying multiple copies of the cluster demonstrated even greater resistance, all of which suggests that "a number of other complex traits are controlled by this type of structural variation."
Also in Science, University of Washington School of Medicine investigators reveal a method by which bacteria populations control the growth of so-called cheaters that use the products secreted by their peers, but do not produce any themselves. Focusing on the opportunistic pathogen Pseudomonas aeruginosa, the team notes that bacteria use a cell-to-cell communication system to control the production of extracellular products that can be used by any other member of the group. Not all bacteria respond to such signals and produce these products, yet the cheaters do not overrun the cooperative bacteria. Through a series of microarray analyses and gene sequencing experiments, the researchers found that the cheaters are incapable of catabolizing the nucleotide adenosine, which is one of the products of partially digested protein. The cooperative bacteria, however, can break down adenosine, giving them an advantage not available to the cheaters. Knowledge of this process could yield new strategies for fighting bacterial infections.
And in a Perspectives piece in this week's issue, a team of researchers discusses how host behavior may be affected by their microbiomes. Much of such work has focused on pathogens, but the team argues that nonpathogenic microbes should also be studied for their effects on their hosts. Recent studies have found that, the article says, fruit flies tend to mate with fruit flies that eat a similar diet and that the gut microbiome in mice "can influence stress, anxiety, and depression-related behavior via effects on the host's neuroendrocrine system." It adds that "the interface between the fields of microbiology and behavior is poised to expand our understanding of complex microbial communities already known to shape animal nutrition and health and to unveil a hidden dimension of animal behavior."