WRKY transcription factor (TF) plays a crucial role in plant abiotic stress response, but it is rarely reported in Michelia crassipes. Our studies have found that the transcription factor McWRKY43, a member of the IIc subgroup, is strongly upregulated under cold stress. In this study, we cloned the full length of McWRKY43 to further investigate the function of McWRKY43 in resistance to cold stress and its possible regulatory pathways in M. crassipes. Under cold stress, the seed-germination rate of transgenic tobacco was significantly higher than that of the wild type, and the flavonoid content, antioxidant enzyme activities, and proline content of transgenic tobacco seedlings were significantly increased, which promoted the expression of flavonoid pathway structural genes. In addition, the transient transformation of McWRKY43 in the M. crassipes leaves also found the accumulation of flavonoid content and the transcription level of flavonoid structural genes, especially McLDOX, were significantly increased under cold stress. Yeast one-hybrid (Y1H) assay showed that McWRKY43 could bind to McLDOX promoter, and the transcription expression of McLDOX was promoted by McWRKY43 during cold stress treatment. Overall, our results indicated that McWRKY43 is involved in flavonoid biosynthetic pathway to regulate cold stress tolerance of M. crassipes, providing a basis for molecular mechanism of stress resistance in Michelia.

Published genome sequences can facilitate multiple genome sequencing studies of flower development, which can serve as the basis for later analysis of variation in flower phenotypes. To identify potential regulators related to flower morphology, we captured dynamic expression patterns under five different developmental stages of petunia flowers, a popular bedding plant, using transcriptome and miRNA sequencing. The significant transcription factor (TF) families, including MYB, MADS, and bHLH, were elucidated. MADS-box genes exhibited co-expression patterns with BBR-BPC, GATA, and Dof genes in different modules according to a weighted gene co-expression network analysis. Through miRNA sequencing, a total of 45 conserved and 26 novel miRNAs were identified. According to GO and KEGG enrichment analysis, the carbohydrate metabolic process, photosynthesis, and phenylalanine metabolism were significant at the transcriptomic level, while the response to hormone pathways was significantly enriched by DEmiR-targeted genes. Finally, an miRNA–RNA network was constructed, which suggested the possibility of novel miRNA-mediated regulation pathways being activated during flower development. Overall, the expression data in the present study provide novel insights into the developmental gene regulatory network facilitated by TFs, miRNA, and their target genes.