The influence of light intensity and photoperiod on duckweed biomass and starch accumulation for bioethanol production

Resurgence of duckweed research and applications: report from the 3rd International Duckweed Conference

Duckweed, flowering plants in the Lemnaceae family, comprises the smallest angiosperms in the plant kingdom. They have some of the fastest biomass accumulation rates reported to date for plants and have the demonstrated ability to thrive on wastewater rich in dissolved organic compounds and thus could help to remediated polluted water resources and prevents eutrophication. With a high quality genome sequence now available and increased commercial interest worldwide to develop duckweed biomass for renewables such as protein and fuel, the 3rd International Duckweed Conference convened at Kyoto, Japan, in July of 2015, to update the community of duckweed researchers and developers on the progress in the field. In addition to sharing results and ideas, the conference also provided ample opportunities for new-comers as well as established workers in the field to network and create new aliances. We hope this meeting summary will also help to disseminate the key advances and observations that have been presented in this conference to the broader plant biology community in order to encourage increased cross-fertilization of ideas and technologies.

Using proteomic analysis to investigate uniconazole-induced phytohormone variation and starch accumulation in duckweed (Landoltia punctata)

BACKGROUND

Duckweed (Landoltia punctata) has the potential to remediate wastewater and accumulate enormous amounts of starch for bioethanol production. Using systematical screening, we determined that the highest biomass and starch percentage of duckweed was obtained after uniconazole application. Uniconazole contributes to starch accumulation of duckweed, but the molecular mechanism is still unclear.

RESULTS

To elucidate the mechanisms of high starch accumulation, in the study, the responses of L. punctata to uniconazole were investigated using a quantitative proteomic approach combined with physiological and biochemical analysis. A total of 3327 proteins were identified. Among these identified proteins, a large number of enzymes involved in endogenous hormone synthetic and starch metabolic pathways were affected. Notably, most of the enzymes involved in abscisic acid (ABA) biosynthesis showed up-regulated expression, which was consistent with the content variation. The increased endogenous ABA may up-regulate expression of ADP-glucose pyrophosphorylase to promote starch biosynthesis. Importantly, the expression levels of several key enzymes in the starch biosynthetic pathway were up-regulated, which supported the enzymatic assay results and may explain why there is increased starch accumulation.

CONCLUSIONS

These generated data linked uniconazole with changes in expression of enzymes involved in hormone biosynthesis and starch metabolic pathways and elucidated the effect of hormones on starch accumulation. Thus, this study not only provided insights into the molecular mechanisms of uniconazole-induced hormone variation and starch accumulation but also highlighted the potential for duckweed to be feedstock for biofuel as well as for sewage treatment.