TITLE:
Impact of Different Light Characteristics on the Growth and Lipid Content of Diatom Phaeodactylum tricornutum Transconjugant Strains
AUTHORS:
Nikunj Sharma, Elisa Ines Fantino, Fatima Awwad, Natacha Mérindol, Arun Augustine, Fatma Meddeb, Isabel Desgagné-Penix
KEYWORDS:
Phaeodactylum tricornutum, Light Condition, Episomal Vector, Dia-toms, Fatty Acids, Biomass
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.14 No.1,
January
20,
2023
ABSTRACT: Light regulates important metabolic processes
in microalgal cells, which can further impact the metabolism and the
accumulation of biomolecules such as lipids, carbohydrates, and proteins.
Different characteristics of light have been studied on various strains of the
model diatom Phaeodactylum tricornutum, but not on transconjugant cells and information on
wild-type strains is still limited. Therefore, we studied the impact of
different light characteristics such as spectral quality, light intensity and
light shift on the growth, and the composition in lipids and fatty acids of P.
tricornutum cells to provide a comprehensive context for future
applications. Initially, we tested the impact of spectral quality and light
intensity on P. tricornutum transformed with an episomal vector (Ptev), harboring the resistance gene Sh ble. Results indicated that Ptev cells accumulated more biomass and
overall lipids in spectral quality Red 1 (R1: 34% > 600 nm > 66%) more
effectively as compared to Red 2 (R2: 8% > 600 nm > 92%). It was also
detected that cell granularity was higher in R1 as compared to R2. Furthermore,
by testing two light intensities 65 μmol·m-2·s-1 and 145 μmol·m-2·s-1 light, it was
observed that 145 μmol·m-2·s-1 led
to an increase in growth trend, total biomass and lipid content. Combining
spectral qualities and light intensities, we show that the lipid accumulation
raised by 2.8-fold. Studying the light intensity and spectral quality allowed
us to optimize the light conditions to R1 spectral quality and light intensity
145 μmol·m-2·s-1. These initial
results showed that red light R1 at 145 μmol·m-2·s-1 was the best condition for biomass and total lipids accumulation in Ptev cells. Next, we further combined
these two-light optimizations with a third light characteristics, i.e. light shift, where the cultures were shifted during the early stationary phase
to a different light environment. We studied Red light shift (Rs) to
investigate how light condition variations impacted P. tricornutum transconjugants Ptev and with an
episomal vector containing the reporter gene YFP (PtYFP). We observed that Rs induced growth and fatty acid
eicosapentaenoic acid (EPA) in Ptev
as compared to PtYFP. Altogether, the
study shows that red light shift of R1 at 145 μmol·m-2·s-1 promoted biomass and total lipids accumulation in Ptev and PtYFP cells. The
study provides a comprehensive approach to using different light
characteristics with the aim to optimize growth and lipids, as well as to fatty
acid production.