Adventitious roots (ARs) have an unmatched status in plant growth and metabolism due to the degeneration of primary roots in lotuses. In the present study, we sought to assess the effect of sucrose on ARs formation and observed that lignin synthesis was involved in ARs development. We found that the lignification degree of the ARs primordium was weaker in plants treated with 20 g/L sucrose than in 50 g/L sucrose treatment and control plants. The contents of lignin were lower in plants treated with 20 g/L sucrose and higher in plants treated with 50 g/L sucrose. The precursors of monomer lignin, including p-coumaric acid, caffeate, sinapinal aldehyde, and ferulic acid, were lower in the GL50 library than in the GL20 library. Further analysis revealed that the gene expression of these four metabolites had no novel difference in the GL50/GL20 libraries. However, a laccase17 gene (NnLAC17), involved in polymer lignin synthesis, had a higher expression in the GL50 library than in the GL20 library. Therefore, NnLAC17 was cloned and the overexpression of NnLAC17 was found to directly result in a decrease in the root number in transgenic Arabidopsis plants. These findings suggest that lignin synthesis is probably involved in ARs formation in lotus seedlings.
Background In China, lotus is an important cultivated crop with multiple applications in ornaments, food, and environmental purification. Adventitious roots (ARs), a secondary root is necessary for the uptake of nutrition and water as the lotus principle root is underdeveloped. Therefore, AR formation in seedlings is very important for lotus breeding due to its effect on plant early growth. As lotus ARs formation was significantly affected by sucrose treatment, we analyzed the expression of genes and miRNAs upon treatment with differential concentrations of sucrose, and a crosstalk between sucrose and IAA was also identified. Results Notably, 20 mg/L sucrose promoted the ARs development, whereas 60 mg/L sucrose inhibited the formation of ARs. To investigate the regulatory pathway during ARs formation, the expression of genes and miRNAs was evaluated by high-throughput tag-sequencing. We observed that the expression of 5438, 5184, and 5345 genes was enhanced in the GL20/CK0, GL60/CK0, and CK1/CK0 libraries, respectively. Further, the expression of 73, 78, and 71 miRNAs was upregulated in the ZT20/MCK0, ZT60/MCK0, and MCK1/MCK0 libraries, respectively. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that most of the differentially expressed genes and miRNAs in the GL20/GL60 and ZT20/ZT60 libraries were involved in signal transduction. A large number of these genes (29) and miRNAs (53) were associated with plant hormone metabolism. We observed an association between five miRNAs (miR160, miR156a-5p, miR397-5p_1, miR396a and miR167d) and nine genes (auxin response factor, protein brassinosteroid insensitive 1, laccase, and peroxidase 27) in the ZT20/ ZT60 libraries during ARs formation. Quantitative polymerase chain reaction (qRT-PCR) was used to validate the high-throughput tag-sequencing data. Conclusions We found that the expression of many critical genes involved in IAA synthesis and IAA transport was changed after treatment with various concentration of sucrose. Based on the change of these genes expression, IAA and sucrose content, we concluded that sucrose and IAA cooperatively regulated ARs formation. Sucrose affected ARs formation by improving IAA content at induction stage, and increased sucrose content might be also required for ARs development according to the changes tendency after application of exogenous IAA.
Background Lotus is an aquatic horticultural crop that is widely cultivated in most regions of China and is used as an important off-season vegetable. The principal root of lotus is degenerated, and adventitious roots (ARs) are irreplaceable for plant growth. We found that no ARs formed under darkness and that exposure to high-intensity light significantly promoted the development of root primordia. Four differential expression libraries based on three light intensities were constructed to monitor metabolic changes, especially in indole-3-acetic acid (IAA) and sugar metabolism. Results AR formation was significantly affected by light, and high light intensity accelerated AR development. Metabolic changes during AR formation under different light intensities were evaluated using gene expression profiling by high-throughput tag-sequencing. More than 2.2 × 104 genes were obtained in each library; the expression level of most genes was between 0.01 and 100 (FPKF value). Libraries constructed from plants grown under darkness (D/CK), under 5000 lx (E/CK), and under 20,000 lx (F/CK) contained 1739, 1683, and 1462 upregulated genes and 1533, 995, and 834 downregulated genes, respectively, when compared to those in the initial state (CK). Additionally, we found that 1454 and 478 genes had altered expression in a comparison of libraries D/CK and F/CK. Gene transcription between libraries D/F ranged from a 5-fold decrease to a 5-fold increase. Twenty differentially expressed genes (DEGs) were involved in the signal transduction pathway, 28 DEGs were related to the IAA response, and 35 DEGs were involved in sugar metabolism. We observed that the IAA content was enhanced after seed germination, even in darkness; this was responsible for AR formation. We also observed that sucrose could eliminate the negative effect of 150 μMol IAA during AR development. Conclusions AR formation was regulated by IAA, even in the dark, where induction and developmental processes could also be completed. In addition, 36 genes displayed altered expression in carbohydrate metabolism and ucrose metabolism was involved in AR development (expressed stage) according to gene expression and content change characteristics.
BackgroundIn China, lotus is an important cultivated crop with multiple applications in ornaments, food, and environmental purification. Adventitious roots (ARs), a secondary root is necessary for the uptake of nutrition and water as the lotus principle root is underdeveloped. To investigate the regulatory pathway during ARs formation, we analyzed the expression of genes and miRNAs upon treatment with differential concentrations of sucrose, and a crosstalk between sucrose and IAA was also identified. ResultsWe observed that the lotus ARs formation was significantly affected by sucrose treatment. Notably, 20 mg/L sucrose promoted the ARs development, whereas 60 mg/L sucrose inhibited the formation of ARs. The expression of genes and miRNAs was evaluated by high-throughput tag-sequencing. We observed that the expression of 5438, 5184, and 5345 genes was enhanced in the GL20/CK0, GL60/CK0, and CK1/CK0 libraries, respectively. Further, the expression of 73, 78, and 71 miRNAs was upregulated in the ZT20/MCK0, ZT60/MCK0, and MCK1/MCK0 libraries, respectively. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that most of the differentially expressed genes and miRNAs in the GL20/GL60 and ZT20/ZT60 libraries were involved in signal transduction. A large number of these genes (29) and miRNAs (53) were associated with plant hormone metabolism. We observed an association between five miRNAs (miR160, miR156a-5p, miR397-5p_1, miR396a and miR167d) and nine genes (auxin response factor, protein brassinosteroid insensitive 1, laccase, and peroxidase 27) in the ZT20/ ZT60 libraries during ARs formation.Quantitative polymerase chain reaction (qPCR) was used to validate the high-throughput tagsequencing data. ConclusionsWe found that the expression of many critical genes involved in IAA synthesis and IAA transport was changed after treatment with various concentration of sucrose. Based on the change of these genes expression, IAA and sucrose content, we concluded that sucrose and IAA cooperatively regulated ARs formation. Sucrose affected ARs formation by improving IAA content at induction stage, and increased
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