Transcriptomics and metabolomics analysis revealed the regulatory network of apical buds development in lotus (Nelumbo nucifera Gaertn.)

Abstract

As a perennial ornamental plant, lotus will begin to become dormant in the face of adverse environmental conditions. The dormancy and apical buds development of lotus are of great significance in regulating the flowering period, storage and reproduction of the lotus rhizome, but the related regulatory mechanisms have not been reported. In this study, we sampled the lotus apical buds at 0 d, 12 d and 24 d after planting, and determined that the lotus could complete the dormancy releaseprocess at 12 days after planting. The monitoring of physiological indexes, hormone levels and transcriptome sequencing of 9 samples in three periods were carried out. It was found that the contents of carbohydrates and hormones changed significantly during apical buds development. Transcriptome analysis also showed that a large number of differentially expressed genes were enriched in hormone synthesis and signal transduction pathways, starch and sucrose metabolism pathways, and lipid metabolism pathways, these genes may be involved in the development of lotus apical buds. Subsequently, we analyzed the differential transcription factors during apical buds development and screened a key differential gene NnHSP18.2. NnHSP18.2 is a heat shock protein (HSP) family gene specifically expressed on apical buds, encoding a protein of 160 amino acids with a conserved α-crystallin domain (ACD) domain. Overexpression of NnHSP18.2 can inhibit Arabidopsis seed germination. These results are of great significance for exploring the molecular mechanism of lotus apical buds development and actively promoting the development of the lotus industry.