Regents Professor Norman Lewis, and fellow researcher and spouse Laurence Davis, shown in the photo above, are holding cuttings from the Arboretum’s Japanese pagoda tree (Sophora japonica or Styphnolobium japonicum planted in 1988) on Friday, June 26, 2020 at the Yakima Area Arboretum.  Professor Lewis and Laurence Davis were collecting samples of Japanese pagoda trees from around the state to help with a research project they are conducting for WSU.

What are the samples being used for?  Professor Norman Lewis and researcher Laurence B. Davin are using Styphnolobium japonicum plant material for their biochemical studies. Inside the plant cells of the wood – there is a very interesting type of isoflavone called a sophorol (the name derives from the original Latin name for the Japanese Pagoda tree, Sophora japonica), which they needed to isolate for their studies.

The sophorals are being isolated to help his team learn more about the successful evolution/adaptation of plants to land, from their aquatic forerunners, over hundreds of millions of years.  This plant evolution created new biochemical pathways. Professor Lewis exclaims that, “this is the domain of the plant phenolics isoflavone – these include substances that produce the cell wall constituents of lignin, that enable plants to stand upright and withstand the forces of gravity and to provide conduits for water/nutrient conduction in the vasculature. Plant phenols are also important players in producing suberin (familiar to us as cork, or the brownish skin that is formed over time on slicing a potato), that enable plants to survive in a desiccating  environment.  Vegetable tannins (many human health protecting) are other important plant phenols, as well as a host of related plant defense molecules (lignans, phytoalexins etc) that can differ depending on the plant family.”

Professor Lewis also goes on to say that their research is, “largely directed to understanding how these different types of plant phenols are formed to give their different metabolic classes. In 1997 in Science, they reported the discovery of a class of proteins that they named dirigent proteins (from the latin dirigere, to guide or align). While these proteins are still largely of unknown biochemical function, what is known thus far is that they guide entry into different plant phenol classes and which, in turn, enabled plants to adapt to land. The dirigent protein products include the structural lignins, the related lignans, some terpenoids, and more recently the anti-fungal phytoalexins (called pterocarpans) that accumulate in legumes.”

Sophorol, in the Japanese Pagoda tree, is needed for their biochemical studies of a dirigent protein sub-family that has enabled phytoalexin formation in legumes, such as in the pea.

Their trip to Yakima was not just to collect Japanese Pagoda tree limbs. On the way, they dropped off some of their other plant samples – stored on dry ice  – that had been originally grown on the International Space Station (ISS) – to the Pacific Northwest National Lab (PNNL) for proteomics analyses. En route, they handed off the ISS samples to fellow collaborator, Kim Hixson. These Space-grown plants were the so-called model plant, Arabidopsis, with different lines having different lignin levels. – to see how they behaved

Norman and Laurence were greatly appreciative of getting the first of their Japanese pagoda tree samples from the Yakima Area Arboretum so they can continue in their quest into discovering how land plants have evolved and adapted. We look forward to learning what comes out of their research too.