Noble plant wins Nobel Prize!

We don’t usually have much cause to celebrate the Nobel Prizes in botany *, so let’s make the most of the 2015 Nobel Prize in Physiology or Medicine. No, it’s not William Campbell and Satoshi Omura’s discoveries relating to “a novel therapy against infections caused by roundworm parasites” – important though that work is. Rather, it’s for the work of the third member of that illustrious trio, Youyou Tu, and her “discoveries concerning a novel therapy against malaria”.

Symptoms of Malaria
Image: Mikael Häggström / Wikipedia.

Malaria is a mosquito-borne infectious disease of humans and other animals caused by parasitic protozoans of the genus Plasmodium. It “remains a worldwide burden that causes hundreds of thousands of deaths every year” (Timothy Wells et al., Nature Reviews Drug Discovery 14: 424–442, 2015), and “may have killed half of all the people that ever lived” (John Whitfield).

The novel therapy is based around use of artemisinin,** a “sesquiterpene lactone with an unusual peroxide bridge” derived from the wormwood plant Artemisia annua. The story of its rediscovery and development as an anti-malarial is eloquently told in phytochemist Youyou Tu’s own words (Nature Medicine 17: 1217-1220, 2011). Prior to artemisinin’s development treatment for malaria was largely due to application of derivatives of another plant-sourced compound, quinine, originally obtained from the Cinchona tree.

Sadly, resistance is developing against the artemisinin-based treatments and the search continues for new effective antimalarial agents. But, as one plant helps treat malaria, another seems to act in the opposite way, as Vincent Nyasembe et al. report in the case of Parthenium hysterophorus, a native of North and South America but now an invasive weed in Africa (PLoS ONE 10(9): e0137836). They found that female Anopheles gambiae mosquitoes accumulated substantial energy reserves when fed on P. hysterophorus. And, given that An. gambiae is the primary mosquito vector responsible for malarial transmission in most of sub-Saharan Africa, this alien plant could therefore help to keep the mosquito alive in the absence of its meal of human blood, thereby adding to even more cases of malaria (apart from other human and livestock issues with this plant – e.g. Seema Patel, 3 Biotech 1:1–9, 2011). Not only do we have to fight malaria directly we also have to resist alien invasions; a tall order indeed!

[Ed. – for more on ‘medicines from plants’, there is also a recent update on the cyclopeptides – circular mini-proteins (absolutely fascinating molecules, and not the usual linear chains we normally think of in the context of proteins) – by Robert Burman et al. (Front. Plant Sci. 6:855).]

* Prompted to review the Nobels’ noble history I’ve identified the following plant-based Prizes:

  • Barbara McClintock “for her discovery of mobile genetic elements” (transposons – ‘jumping genes’ (Sandeep Ravindran, PNAS 109: 20198-20199, 2012)) – in maize; Physiology or Medicine (1983)
  • Norman E. Borlaug “for his work in enhancing grain production in the 1940s and 1950s which has been hailed as the Green Revolution”; Peace Prize (1970)
  • Melvin Calvin “for his research on the carbon dioxide assimilation [i.e. photosynthesis] in plants”; Chemistry (1961)
  • Sir Robert Robinson “for his investigations on plant products of biological importance, especially the alkaloids” – but who also has a malarial connection; Chemistry (1947)
  • Hans Fischer “for his researches into the constitution of haemin and chlorophyll and especially for his synthesis of haemin”; Chemistry (1930)
  • Richard Martin Willstätter “for his researches on plant pigments, especially chlorophyll”; Chemistry (1915)

From that rigorous analysis we can conclude that, if you want to be in with a good chance for a Nobel for your botany, it needs to be (bio)chemical. As an aside, it’s noteworthy that >100 years ago Ronald Ross gained the Nobel for Physiology or Medicine in 1902 “for his work on malaria, by which he has shown how it enters the organism and thereby has laid the foundation for successful research on this disease and methods of combating it”.

** as hard to spell properly as I find this word, its full scientific name of (3R,5aS,6R,8aS,9R,12S,12aR)-Octahydro-3,6,9-trimethyl-3,12-epoxy-12H-pyrano[4,3-j]-1,2-benzodioxepin-10(3H)-one is probably even harder to get right – and remember.