Sulfur limitation boosts more starch accumulation than nitrogen or phosphorus limitation in duckweed (Spirodela polyrhiza).

Duckweeds contain high levels of starch and are environmentally sustainable and economically viable feedstock for biofuel production. Here, the biomass and starch yield of three duckweed species under three different nutrient-limited conditions were analyzed to investigate the possible ways of further increasing the efficiency of starch production. The results showed that sulfur limitation resulted in the highest starch yield, which was 42% and 73% higher than in nitrogen or phosphorus limitation conditions, respectively. The high yield of sulfur-limited duckweed is largely due to the combinations of little effects on biomass and high accumulations of starch. Although nitrogen limitation led to higher starch content (67.4%), it severely reduced biomass production. Besides, this work revealed the mechanism of starch accumulation induced by sulfur limitation in duckweed based on transcriptomic analysis. In summary, sulfur limitation is a practical approach to increase starch yields in duckweed without affecting growth or biomass production. • Sulfur limitation induces starch production without inhibiting growth of duckweed. • Starch content was as high as 56.2% of dry weight under sulfur limitation. • Sulfur limitation results in the highest starch yield in three duckweed species. • SDI1 and bZIP17 were identified for improving starch yield by genetic engineering. • The mechanism of sulfur limitation-induced starch accumulation was elucidated. [ABSTRACT FROM AUTHOR]