Abstract
BackgroundTea plant (Camellia sinensis) is one of the most popular non-alcoholic beverages worldwide. In tea, lateral roots (LRs) are the main organ responsible for the absorption of moisture and mineral nutrients from the soil. Lateral roots formation and development are regulated by the nitrogen and auxin signaling pathways. In order to understand the role of auxin and nitrogen signaling in LRs formation and development, transcriptome analysis was employed to investigate the differentially expressed genes involved in lateral roots of tea plants treated with indole-3-butyric acid (IBA), N-1-naphthylphthalamic acid (NPA), low and high concentrations of nitrogen.ResultsA total of 296 common differentially expressed genes were identified and annotated to four signaling pathways, including nitrogen metabolism, plant hormone signal transduction, glutathione metabolism and transcription factors. RNA-sequencing results revealed that majority of differentially expressed genes play important roles in nitrogen metabolism and hormonal signal transduction. Low nitrogen condition induced the biosynthesis of auxin and accumulation of transcripts, thereby, regulating lateral roots formation. Furthermore, metabolism of cytokinin and ethylene biosynthesis were also involved in lateral roots development. Transcription factors like MYB genes also contributed to lateral roots formation of tea plants through secondary cell wall biosynthesis. Reversed phase ultra performance liquid chromatography (RP-UPLC) results showed that the auxin concentration increased with the decreased nitrogen level in lateral roots. Thus, tea plant lateral roots formation could be induced by low nitrogen concentration via auxin biosynthesis and accumulation.ConclusionThis study provided insights into the mechanisms associated with nitrogen and auxin signaling pathways in LRs formation and provides information on the efficient utilization of nitrogen in tea plant at the genetic level.
Highlights
Tea plant (Camellia sinensis) is one of the most popular non-alcoholic beverages worldwide
The aboveground parts of seedlings treated with No nitrogen (NN), low nitrogen (LN) and high nitrogen (HN) were shorter than the control (Fig. 1)
The leaves of the seedlings showed brownish colouration (Fig. 2c, Fig. 3). This suggests that exogenous auxin could avoid the inhibition of the lateral roots (LRs) growth with HN treatment in tea plant
Summary
Tea plant (Camellia sinensis) is one of the most popular non-alcoholic beverages worldwide. Lateral roots formation and development are regulated by the nitrogen and auxin signaling pathways. In order to understand the role of auxin and nitrogen signaling in LRs formation and development, transcriptome analysis was employed to investigate the differentially expressed genes involved in lateral roots of tea plants treated with indole-3-butyric acid (IBA), N-1-naphthylphthalamic acid (NPA), low and high concentrations of nitrogen. Nitrogen supplying has a strong correlation with auxin synthesis and metabolism These reports have provided a clear basis for further exploration of the regulatory relationship between nitrogen metabolism-related genes and plant LRs growth. Most of these studies focused on the model plant Arabidopsis thaliana only, and rarely included woody plants
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