Lingling Shang, originally from China, moved to Quebec City, Canada in 2013. She got a bachelor degree in Shandong Agriculture University in Shandong Province, China in 2010, and a master degree in China Agriculture University in Beijing, China in 2012. She worked at Syngenta Inc. as a trainee for one year, and then started Ph.D. studies at Laval University in 2013, with the personal objective of improving her skills and becoming an expert in plant science. The main focus of her work is to increase recombinant protein yields in plant expression platforms by the optimization of environmental factors in controlled environments.
Plants are now proven production hosts for biopharmaceuticals and extensive research has been done over the last decade to develop molecular tools for recombinant protein yield improvement. Despite major advances, little is known about the effects of basic environmental parameters on plant biomass production prior to protein expression. In this study, we investigated three important environmental factors, atmospheric CO2 concentration, photosynthetic photon flux density (PPFD) and different ratios of ammonium supply, on growth and development of the plant protein expression host Nicotiana benthamiana transiently transformed to express influenza virus hemagglutinin in the form of virus-like particles (HA-VLPs), in leaf tissue. High PPFD, CO2 enrichment and high ammonium supply increased leaf fresh weight during plant growth phase, before Agrobacterium infiltration for protein expression. High PPFD and CO2 enrichment also increased fresh weight at harvest (following the 6-day protein expression phase), but a high ammonium supply had the opposite effect. On a leaf fresh weight basis, high ammonium supply increased the content of both total soluble protein (TSP) and large Rubisco (RbcL) subunit, but had no effect on HA-VLP content. High PPFD had no effect on TSP and RbcL but decreased HA-VLP content, compared to CO2 enrichment having no effect on TSP, RbcL and HA-VLP contents. On a plant basis, high ammonium supply increased RbcL content, decreased HA-VLP accumulation level under low PPFD and had no effect on TSP content. High PPFD significantly increased TSP and RbcL contents but decreased HA-VLP content at normal ammonium supply. CO2 enrichment had a slight positive effect on TSP and RbcL contents but no effect on HA-VLP accumulation level. In addition, the increase in TSP content under high PPFD (significant) and CO2 enrichment (tendency) correlated with the increase in RbcL. HA yield was not positively affected under those conditions.