Enhancement of methyl salicylate accumulation promotes early flowering in transgenic tobacco plants by overexpressing a carboxymethyl transferase (SAMT) gene from Lycium chinense

Abstract

Flowering time is an important agronomic trait, which is of great significance to the plant growth process. Salicylic acid (SA) is a key hormone that regulates plant growth and development. It can be converted into methyl salicylate (MeSA) catalyzed by SA carboxymethyl transferase (SAMT). Previous studies showed that SA was related to the regulation of plant flowering; however, the specific mechanism associated with this process remained to be further elucidated. In this study, the transgenic tobacco overexpressing LcSAMT gene and WT tobacco were cultivated to observe the flowering status of plant. The biomass and growth of tobaccos were recorded at different stages of plant growth. Endogenous MeSA content, phenylalanine ammonia-lyase (PAL) activity, and anthocyanin content were determined in transgenic tobacco plants during flowering stage. It was observed that the flowering time of transgenic tobacco was usually 6–7 days earlier than WT tobacco, and a higher endogenous MeSA content, PAL activity, and anthocyanin content were found in transgenic tobacco plants during flowering stage. Quantitative real-time PCR (qPCR) and transcriptome analysis were also performed in this study. There were 3924 differentially expressed genes (DEGs) identified between WT and transgenic tobacco plants by transcriptome analysis. These DEGs were primarily associated with plant hormone signal transduction pathways, plant pathogen interaction pathways, and mitogen-activated protein kinase (MAPK) pathways. QPCR analysis of 15 DEGs revealed that these genes were markedly upregulated in transgenic tobacco which was in accordance with transcriptome sequencing results. This study indicated that the SAMT gene-mediated SA homeostasis played important roles in the regulation of tobacco flowering.