Zhu Yerong, Li Xiaoxue, Gao Xuan, Sun Jiqi, Ji Xiaoyuan, Feng Guodong, Shen Guangshuang, Xiang Beibei, Wang Yong
College of Life Science, Nankai University, Weijin Road 94, Tianjin, 300071, China.
School of Chinese Material Medica, Tianjin University of Traditional Chinese Medicine, Poyang Lake Road 10, Tianjin, 301617, China.
Biotechnol Biofuels. 2021 Apr 19;14(1):99. doi: 10.1186/s13068-021-01932-y.
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. However, the molecular explanation on the mechanism of MH action is still unclear.
To 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 I-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.
The 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.
浮萍因其高生物量和淀粉产量而被认为是生物乙醇生产的一种有前景的原料。在营养繁殖受到抑制后，植物生长调节剂可以提高淀粉含量。据报道，马来酰肼（MH）可抑制植物生长，同时增加某些植物的生物量和淀粉含量。然而，关于MH作用机制的分子解释仍不清楚。
为了解MH对多根紫萍7498生长和淀粉积累的影响及作用方式，用不同浓度的MH处理植株。我们的结果表明，MH处理后，叶状体和根的生长均受到显著抑制，植株淀粉含量增加。在75 μg/mL MH处理且实验第8天时，淀粉含量最高，约为40 mg/g鲜重，比对照高约20倍。碘-碘化钾染色和透射电镜结果证实，75 μg/mL MH处理的叶状体比对照含有更多的淀粉和大淀粉粒。光合色素含量和PSII叶绿素荧光参数均无显著差异。对75 μg/mL MH处理后的多根紫萍7498进行差异表达转录本分析。结果表明，一些与生长素反应相关的基因表达下调；而一些参与碳固定、光合作用C4途径、淀粉生物合成和脱落酸信号转导途径的基因表达上调。
这些结果为MH处理抑制生长和积累淀粉的潜在机制提供了新的见解，并为提高浮萍淀粉产量提供了一种选择方法。
