Transcriptome analysis reveals the mechanism of NaHCO₃ promoting tobacco leaf maturation

NaHCO₃ accelerates the aging of tobacco leaves; however, the underlying molecular mechanisms have not been elucidated. This study aimed to explore the mechanism of NaHCO₃ in the promotion of tobacco leaf maturation using transcriptome analysis. Leaves on plants or detached leaves of the tobacco variety, Honghua Dajinyuan, were sprayed with or without 1% NaHCO₃. The leaf yellowing was observed, the pigment content and enzyme activities were determined and RNA sequencing (RNA-seq) was performed. Spraying NaHCO₃ onto detached leaves was found to promote leaf yellowing. Pigment content, catalase activity, and superoxide dismutase activity significantly decreased, whereas peroxidase activity and malondialdehyde content significantly increased. RNA-seq demonstrated that spraying with NaHCO₃ upregulated genes associated with cysteine and methionine metabolism; alpha-linolenic acid metabolism; and phenylalanine, tyrosine, and tryptophan biosynthesis and downregulated genes related to photosynthesis and carotenoid biosynthesis. Genes correlated with autophagy-other, valine, leucine, and isoleucine degradation, and the MAPK signaling pathway were upregulated while those correlated with DNA replication, phenylalanine, and tyrosine and tryptophan biosynthesis were downregulated in detached leaves sprayed with NaHCO₃ compared with the plant leaves sprayed with NaHCO₃. Overall, this study is the first to elucidate the molecular and metabolic mechanisms of NaHCO₃ in the promotion of tobacco leaf maturation.