Qingqing Liu

ABC transporters (ATP-binding cassette transporters) constitute one of the largest known protein families and are widely distributed in plants. Their primary function involves utilizing energy derived from ATP hydrolysis to transport substrates across membranes against concentration gradients. These transporters play crucial roles in the translocation and accumulation of metabolites, stress tolerance, disease resistance, and plant defense. Lotus is an important traditional Chinese medicinal herb and contains active ingredients primarily composed of secondary metabolites, whose transport and accumulation require the involvement of ABC transporters. However, the function of these ABC transporters remains unexplored in lotus. In this study, 122 ABC transporter genes were predicted within the lotus genome. We identified 1~15 conserved motifs among the NnABC proteins and most of them were stable proteins predominantly located on the plasma membrane with ExPASy-ProtParam, ProComp and WoLF PSORT analysis. Phylogenetic tree analysis revealed that the lotus ABC transporter gene family could be divided into eight subfamilies, from ABCA to ABCI, and the evolution was predominantly driven by purifying selection. Comparative transcriptome analysis between the cultivar ‘Yindu Zhimi’ with orange-reddish stamen and ‘Weishan Hong’ with yellowish stamen, along with quantitative real-time PCR results, showed that the NnABCG25 gene is highly specifically expressed in the orange-reddish stamen. Molecular docking demonstrated that NnABCG25 has a stable affinity for lycopene, β-carotene and β-apocarotenal, suggesting its potential involvement in the transport of carotenoids in the stamen. These findings expand our understanding of the role of ABC transporters in the transport and accumulation of carotenoids, as well as providing a valuable reference for research on the ABC transporter gene family in other plants.

Compared with rose, chrysanthemum, and water lily, the absence of short-wide and long-narrow tepals of ornamental lotus (Nelumbo Adans.) limits the commercial value of flowers. In this study, the genomes of two groups of lotus mutants with wide-short and narrow-long tepals were resequenced to uncover the genomic variation and candidate genes associated with tepal shape. In group NL (short for N. lutea, containing two mutants and one control of N. lutea), 716,656 single nucleotide polymorphisms (SNPs) and 221,688 insertion-deletion mutations (Indels) were obtained, while 639,953 SNPs and 134,6118 Indels were obtained in group WSH (short for ‘Weishan Hong’, containing one mutant and two controls of N. nucifera ‘Weishan Hong’). Only a small proportion of these SNPs and Indels was mapped to exonic regions of genome: 1.92% and 0.47%, respectively, in the NL group, and 1.66% and 0.48%, respectively, in the WSH group. Gene Ontology (GO) analysis showed that out of 4890 (NL group) and 1272 (WSH group) annotated variant genes, 125 and 62 genes were enriched (Q < 0.05), respectively. Additionally, in the Kyoto Encyclopedia of Genes and Genomes (KEGG) database, 104 genes (NL group) and 35 genes (WSH group) were selected (p < 0.05). Finally, there were 306 candidate genes that were sieved to determine the development of tepal shape in lotus plants. It will be an essential reference for future identification of tepal-shaped control genes in lotus plants. This is the first comprehensive report of genomic variation controlling tepal shape in lotus, and the mutants in this study are promising materials for breeding novel lotus cultivars with special tepals.

The lotus (Nelumbo Adans.) is an important aquatic plant with ornamental, medicinal and edible values and cultural connotations. It has single-, semi-double-, double- and thousand-petalled types of flower shape and is an ideal material for developmental research of flower doubling. The lotus is a basal eudicot species without a morphological difference between the sepals and petals and occupies a critical phylogenetic position in flowering plants. In order to investigate the genetic relationship between the sepals and petals in the lotus, the class E genes which affect sepal formation were focused on and analyzed. Here, SEPALLATA 1(NnSEP1) and its homologous genes AGAMOUS-LIKE MADS-BOXAGL9 (NnAGL9) and MADS-BOX TRANSCRIPTION FACTOR 6-like (NnMADS6-like) of the class E gene family were isolated from the flower buds of the Asian lotus (Nelumbo nucifera Gaertn.). The protein structure, subcellular localization and expression patterns of these three genes were investigated. All three genes were verified to locate in the nucleus and had typical MADS-box characteristics. NnSEP1 and NnMADS6-like were specifically expressed in the sepals, while NnAGL9 was highly expressed in the petals, suggesting that different developmental mechanisms exist in the formation of the sepals and petals in the lotus. The significant functional differences between NnSEP1, NnMADS6-like and NnAGL9 were also confirmed by a yeast two-hybrid assay. These results expand our knowledge on the class E gene family in sepal formation and will benefit fundamental research on the development of floral organs in Nelumbo.