Plants are an ancient, rich and sustainable source of natural chemodiversity in the form of alkaloids, terpenoids, flavonoids, tannins and other classes of small-molecular-weight compounds (phytochemicals). Lacking the adaptive immunity of animals, plants evolved to rely on small molecules for their survival, proliferation and reproduction. Rigorous and ever-shifting evolutionary pressures shaping both chemical structures and relative abundances of phytochemicals underscore the fact that these molecules will continue finding novel applications in numerous venues that aim to improve our quality of life and health. Thus, in addition to the well-recognized uses of phytochemicals in healthcare, both traditional and modern, many other industries (food and beverage, cosmetics, agriculture, polymer, energy, etc.) are currently proactively researching opportunities for replacing synthetic or fossil materials by those derived from plants and other sustainable biological sources, with the anticipation that these alternatives will provide positive gains in consumer safety, environmental impact and sustainability. In fact, the vision of a bio-based economy of a non-dystopian post-fossil future aims to use plant-derived resources for energy, medicine, materials and many other essential needs.
The central element of this economy is the use of intelligent 'bio-refineries', where renewable resources will be converted into a range of value-added products. Development of such bio-refineries requires technological innovation in bio-prospecting (searching for new materials with useful properties in organisms) for a guided discovery of reliable, cost-effective and sustainable feedstock opportunities. And since it has been estimated that only a small portion (less than 10%) of more than 250,000 plant species on the planet has been interrogated to any extent for phytochemical content, there remain vast prospects for the discovery of novel molecular entities with unprecedented properties and/or valorization potential, especially in underexplored ecological and taxonomic domains, and for currently underutilized or wasted materials, such as the so-called 'agricultural residue'. There are also other important corollary benefits of bio-prospecting relevant for this project. Plant-derived materials are expected to have a generally superior safety profile than synthetics for humans, livestock, pets and environment in general, being produced by fellow eukaryotes. For threatened habitats, bioprospecting could support an important mission of preserving biodiversity, and, considering recent de-emphasis of natural products by pharmaceutical industry, academia could step in and fill the potentially richly rewarding discovery niche. High-throughput bio-prospecting of whole plants for useful compounds presents, however, numerous challenges in both accessibility of diverse collections amenable for regular feedstock harvests and batch-to-batch control over phytochemical content, which could vary significantly depending on geographic, seasonal, agronomic, microbiological and many other factors. Moreover, certain types of plants--toxic, endangered, protected, uncultivable, disease-transmitting or invasive--may not be easily tractable for such efforts.
Plant cell culture technology is an emerging alternative approach that promises to overcome most, if not all, of these limitations, whereby dedifferentiated (callus) cultures are established from different plant tissues and grown sustainably in liquid or on solid media. A recent (2014) donation of the one-of-the-kind 2,280-species-strong Plant Cell Culture Library (PCCL) to the University of Massachusetts has enabled access by the academic community at large to a vast and taxonomically diverse collection of sustainably cultivable callus cell lines. This collection has a potential to solve the key challenges of working with whole plants: access to a high level of biological diversity, exquisite control over experimental reproducibility and ability to manipulate secondary metabolism with ecologically meaningful elicitation tactics. We view this variable responsiveness of plant surrogates to specific external stimuli (elicitors) as an opportunity to enrich in a rational fashion chemical diversity displayed by the biologically diverse collection. One potentially significant limitation of the collection is that it does not reflect well the biodiversity of the local flora. Altogether, less than 5% of PCCL species can be attributed to plants that are either native to or commonly cultivated in Massachusetts, which currently restricts feedstock scale-up potential in any bio-prospecting efforts involving the PCCL collection, and limits its value to the scientific and agricultural communities at the University of Massachusetts (UMass) and New England region in general.
