Growth and Transcriptomics Analysis of Michelia macclurei Dandy Plantlets with Different LED Quality Treatments

Michelia macclurei Dandy is a significant tree species that has extensive cultivation for forestry and horticulture purposes in southern China, owing to its economic and practical importance. Light quality influences plantlet growth and development during tissue culture. However, the growth characteristic and molecular regulation of M. macclurei under different light quality conditions are not well understood yet. In this study, we investigated the morphological, chlorophyll content, and transcriptomic responses of M. macclurei plantlets under different light-emitting diode (LED) qualities, including white, blue, and red light. The results showed that blue light significantly increased plant height (21.29%) and leaf number (18.65%), while red light decreased plant height and leaf number by 7.53% and 16.49%, respectively. In addition, the plantlets’ chlorophyll content and etiolation rate were significantly reduced by blue and red light quality compared to white light. Compared to white light, blue light had a negative effect, leading to decreased rooting rate (64.28%), root number (72.72%), and root length (75.86%). Conversely, red light had a positive effect, resulting in increased rooting rate (24.99%), root number (109.58%), and root length (72.72%). Transcriptome analysis identified 54 differentially expressed genes (DEGs) in three groups that consisted of blue light vs. white light (BL-vs-WL), red light vs. white light (RL-vs-WL), and red light vs. blue light (RL-vs-BL). Specifically, 21, 7, and 41 DEGs were identified in the three groups, respectively. The DEGs found in the RL-vs-WL and BL-vs-WL groups were involved in plant hormone signaling, nitrogen metabolism, and phenylpropanoid biosynthesis pathways, which suggests that M. macclurei plantlets adapt to the changes of light quality via modulating gene expression. Overall, our study provides valuable insights for understanding the molecular and morphological responses of M. macclurei plantlets under different light qualities.