Kingdom-blurring discovery

This column is always interested in cross-Kingdom co-operation (especially if it involves plants!), but some ‘associations’ go too far, and often in weirdly and wonderfully unexpected covert ways and make you wonder where one kingdom ends and another begins. Take, for instance, the news that microRNAs from dietary staples such as rice can not only be found in the blood and tissues of humans and other plant-eating mammals, but that those botanical biomolecules may actually influence gene expression in their new hosts. Lin Zhang and colleagues found that MIR168a, which is highly enriched in rice, inhibits a protein that helps remove low-density lipoprotein (LDL) from the blood (Cell Research), at least in mice. If more widely applicable this finding is likely to have implications for dietary management of cholesterol levels in humans since elevated amounts of LDLs are associated with health problems such as cardiovascular disease. Perhaps this is the plant way of telling us not to eat them after all? And this is on the back of news that ribosomes may exert control over what RNAs they actually ‘decide’ to translate. Working with mice, Nadya Kondrashov et al. present evidence that ribosomes can regulate gene expression, in some instances (Cell, 2011). Famously, ribosomes are largely considered ‘just’ to facilitate the translation of messenger RNA into polypeptide chains during protein synthesis by providing a physical substrate where this can take place (yes, I know I’m simplifying it a bit; ). This work is regarded highly enough to have been post-publication peer-reviewed by the Faculty of 1000. I don’t know, which bit of the cell is in control? Is this now an example of feed-back, or feed-forward? Either way, it seems that the more you dig the more you find that it’s feeding every which way. In any event, this represents another ‘trophy’ for the cell biology hall of fame. By way of turning the tables somewhat away from plants and back in favour of animals, Jonathan Kingdon and colleagues tell the tale of the African crested rat (Proceedings of the Royal Sociey, B;– spot the seamless mouse–rat link?). This rodent has developed the interesting trait of ‘unpalatability by appropriation’ in which it gnaws, masticates and slavers toxins acquired from the roots and bark of Acokanthera schimperi (Apocynaceae) onto highly specialised hairs. The poison (a cardenolide, closely resembling ouabain) is one of the active components in a traditional African arrow poison long celebrated for its power to kill elephants(!). But being a sporting kind of critter, ‘Ratty’ advertises its possession of this particularly potent plant poison to would-be attackers.