Grand opportunities in physiology to address the grand challenges facing the planet

Abstract

For people, plants can seem like aliens. Movements are typically slow, and many consider plants “slow and low life [sLow life]” (Hangarter, 2009). Their appearance and behavior are so different from ourselves that we are in awe when we learn that many of the central functions of plants and humans are encoded by highly conserved genes. For example at the core of metabolism, hexokinase, the enzyme that phosphorylates incoming glucose, and many of the proteins that transport glucose look strikingly similar. This similarity goes yet deeper, as hexokinase has two distinct functions both as an enzyme and as a sensor (“sensyme”), a duality that appears to be conserved from plants to fungi to animals (Frommer et al., 2003). In a second example, the identification of the first higher plant ammonium transporter allowed a function to be assigned for the first time to an important human locus – the Rhesus factor (Ninnemann et al., 1994; Marini et al., 1997). One of the most recent and striking examples of functional similarities was the finding that both plants and animals use carbonic anhydrase to sense carbon dioxide – in humans permitting champagne bubbles to be tasted, and in plants crucial for control over the gas exchange with the atmosphere (Frommer, 2010). McGary et al. (2010) found that plants and people share at least 48 functional modules; sets of genes that act in common to produce a phenotype. Many of these are disease-related. “There was a lot of screaming in the halls for that one [sic what was conceived as unexpected similarity]” as Edward Marcotte, a cancer researcher at the University of Texas, stated in the New York Times (Zimmer, 2010). This “deep homology” in functional networks, identified through the use of large datasets from the TAIR Arabidopsis database (www.arabidopsis.org/) argues strongly that research in plants can not only unravel the secrets of plants, but can guide research in metazoan organisms. It is apparently a consequence of evolution, where much remains to be learned about the first ancestors of multicellular green organisms and the mechanisms that had to evolve to allow for efficient photosynthesis, gas exchange, efficient mining of mineral nutrients and multicellularity.