Abstract
BackgroundDuckweed is considered a promising feedstock for bioethanol production due to its high biomass and starch production. The starch content can be promoted by plant growth regulators after the vegetative reproduction being inhibited. Maleic hydrazide (MH) has been reported to inhibit plant growth, meantime to increase biomass and starch content in some plants. However, the molecular explanation on the mechanism of MH action is still unclear.ResultsTo know the effect and action mode of MH on the growth and starch accumulation in Spirodela polyrrhiza 7498, the plants were treated with different concentrations of MH. Our results showed a substantial inhibition of the growth in both fronds and roots, and increase in starch contents of plants after MH treatment. And with 75 µg/mL MH treatment and on the 8th day of the experiment, starch content was the highest, about 40 mg/g fresh weight, which is about 20-fold higher than the control. The I2-KI staining and TEM results confirmed that 75 µg/mL MH-treated fronds possessed more starch and big starch granules than that of the control. No significant difference for both in the photosynthetic pigment content and the chlorophyll fluorescence parameters of PII was found. Differentially expressed transcripts were analyzed in S. polyrrhiza 7498 after 75 µg/mL MH treatment. The results showed that the expression of some genes related to auxin response reaction was down-regulated; while, expression of some genes involved in carbon fixation, C4 pathway of photosynthesis, starch biosynthesis and ABA signal transduction pathway was up-regulated.ConclusionThe results provide novel insights into the underlying mechanisms of growth inhibition and starch accumulation by MH treatment, and provide a selective way for the improvement of starch production in duckweed.
Highlights
Duckweed is considered a promising feedstock for bioethanol production due to its high biomass and starch production
Effect of Maleic hydrazide (MH) on parameters related to light reactions To figure out the reasons for starch accumulation after MH treatment, we investigated parameters related to light reactions of photosynthesis
We found that IAA22-like, IAA27 and IAA30 (IAA30-like) were all down-regulated in S. polyrrhiza 7498 after MH treatment (Table 2)
Summary
Duckweed is considered a promising feedstock for bioethanol production due to its high biomass and starch production. The starch content can be promoted by plant growth regulators after the vegetative reproduction being inhibited. Maleic hydrazide (MH) has been reported to inhibit plant growth, meantime to increase biomass and starch content in some plants. Duckweeds (Lemnaceae) are among the known smallest flowering plants, which are aquatic, propagate mainly via asexual reproduction, and most importantly grow more rapidly than other higher plants [1,2,3]. We explored the effect and mechanism of MH on inhibiting growth in plants of Spirodela polyrrhiza 7498, the first duckweed species used for genome sequencing, as an appropriate concentration can promote starch content, which is very feasible in the application of bioenergy production of duckweed plants [3, 16, 17, 30]
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