Auxin regulates bulbil development by affecting carbohydrate metabolism in Lilium lancifolium

Lily bulbils originate from the leaf axils of the middle and upper stems of lilies and play an important role in the reproduction of triploid Lilium lancifolium. The development process of lily bulbils results from cell division and expansion, but the roles of plant hormones and carbohydrate metabolism remains unclear. In this study, we treated L. lancifolium with exogenous indole-3-acetic acid (IAA) and the auxin polar transport inhibitor N-1-naphthylphthalamic acid (NPA) and analyzed morphology, transcriptomics, and gene function during bulbil development. The IAA treatment increased the bulbil diameter and total weight per plant, promoting bulbil development. By constructing an association network of characters and modules, we found that bulbil diameter was significantly negatively correlated with the black module genes and positively correlated with the yellow module genes, which are related to plant hormone and carbohydrate metabolism. We identified key genes in the bulblet system due to bulbil and bulblet development similarities. Silencing the LlSAUR36 and LlIAA10 genes in the auxin signaling pathway inhibited bulblet development. In the carbohydrate metabolism pathway, we identified two key genes using silencing methods, LlTPS1 and LlCSLC5, resulting in phenotypes similar to LlSAUR36 and LlIAA10, which inhibited bulbil development. In conclusion, auxin signaling engages in the bulbil development of L. lancifolium by regulating key carbohydrate metabolism genes. This study provides a molecular basis for developing lily bulbils and offers useful clues for the future development of new lily bulbil production methods.