Identification and expression profiling of rosmarinic acid biosynthetic genes from Satureja khuzistanica under carbon nanotubes and methyl jasmonate elicitation

Satureja khuzistanica is a medicinal herb endemic to Iran which can serve as a source of rosmarinic acid (RA). In the present study, the effect of different concentrations of methyl jasmonate (MeJA) and multi-walled carbon nanotubes (MWCNTs) on the rosmarinic acid accumulation and the expression of genes involved in its biosynthetic pathway was evaluated in nodal segment cultures of S. khuzistanica. The concentration of RA varied in plant extracts derived from the field, plants obtained under in vitro solid media, calli, suspension cultures and nodal segment cultures in liquid medium, with the highest amount recorded in nodal segment cultures. Phenylalanine ammonia-lyase (PAL), tyrosine aminotransferase (TAT), 4-hydroxyphenylpyruvate reductase (HPPR) and RA synthase (RAS) cDNA clones as key biosynthetic genes of RA production were identified and expression patterns were assayed in response to MeJA and MWCNTs, exogenously applied at a range of 0, 50, 100, 250mg L-1. The expression levels of HPPR, PAL and TAT were up-regulated at 100mg L-1 MWCNTs, whereas down-regulated levels were observed at 250mg L-1. RAS was up-regulated in all MWCNTs treatments. HPPR, PAL and TAT expression increased sharply at 250mg L-1 MeJA. The highest levels of RAS transcripts were observed at 100mg L-1 MeJA. The highest HPPR, PAL and TAT expression levels were observed at 250mg L-1 MeJA. In accordance, HPLC analysis showed a high amount of RA under MeJA and MWCNT elicitors. Our results provide helpful information on the expression profiles of biosynthetic genes in connection with RA accumulation.