# Transcriptome analysis reveals the mechanism of NaHCO3 promoting tobacco leaf maturation

## TL;DR

This study uses transcriptome analysis to uncover how NaHCO3 promotes tobacco leaf maturation by affecting gene expression and enzyme activity.

## Contribution

The study is the first to elucidate the molecular and metabolic mechanisms of NaHCO3 in promoting tobacco leaf maturation.

## Key findings

- Spraying NaHCO3 promotes leaf yellowing and alters enzyme activities like peroxidase and catalase.
- RNA-seq shows upregulation of genes related to cysteine metabolism and downregulation of photosynthesis-related genes.
- Detached leaves show distinct gene expression patterns compared to plant leaves when treated with NaHCO3.

## Abstract

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.