Alkaloids production and antioxidant properties in Catharanthus roseus (L.) G. Don. shoots and study of alkaloid biosynthesisrelated gene expression levels in response to methyl jasmonate and putrescine treatments as ecofriendly elicitors. Biol. Fut. 70,[38][39][40][41][42][43][44][45][46]

No abstract

To compare the effects of different carbon sources on physiological aspects, especially medicinal alkaloid biosynthesis and related gene expression in Catharantus roseus (L.) G.Don, we employed sucrose and sorbitol with two concentrations (87.64 mM, the equimolar concentration of sucrose in MS basal medium, and 150 mM) on the plant’s shoots in vitro in presence of 100 μM methyl jasmonate. The production of plant alkaloids including vincristine, vinblastine, ajmalicine, vindoline and catharantine and their biosynthetic and regulatory gene expression was measured. Both treatments had incremental effects on alkaloid production, upregulated the mitogen-activated protein kinase3 (MAPK3) and a downstream responsive transcription factor, ORCA3, which resulted in elevated transcript contents of the important genes in terpenoid indol alkaloids biosynthetic pathway including peroxidase1 (PRX1), geissoschizine synthase (GS), strictosidine synthase (STR) and deacetylvindoline acetyltransferase (DAT). Defensive responses such as antioxidant enzymes (catalase, peroxidase and superoxide dismutase) activities and non-enzymatic metabolites (total phenolics, flavonoids and carotenoids) contents increased under both treatments but the effects of sorbitol were stronger. Reduced fresh weight and chlorophylls contents, increased malondialdehyde (MDA) and carotenoid contents were shown after a week under all employed treatments. It seems that replacement of sucrose with sorbitol and also, increased concentrations of both carbon sources via increasing osmotic pressure make stressful conditions for the plant especially in longer times.

This study aimed to determine the effects of methyl jasmonate (Mj) combined with chromium (Cr) as elicitor on production of medicinal alkaloids, its antioxidant potential, and its effects on the expression of signaling and biosynthetic enzymes. Combined treatment had positive effects on secondary metabolism and changed genes expression levels of mitogen-activated protein kinase 3 (<em>MAPK3</em>), a transcription factor (TF) known as octadecanoid-responsive <em>Catharanthus</em> AP2-domain 3 (<em>ORCA3</em>) upstream of plant alkaloids biosynthetic pathway. Maximum expression levels of peroxidase1 (<em>PRX1</em>)<em>, </em>geissoschizine synthase (<em>GS</em>) (24 h-treatment), <em>MAPK3</em> and <em>ORCA3 </em>(8 h-treatment)<em>, </em>were 6.25−, 4.87-, 7.67-, and 5.38-fold higher than control, respectively, in response to 100 µM Mj + 50 µM Cr. This value was 5.92-fold for strictosidine synthase (<em>STR</em>) in response to 100 µM Mj + 100 µM Cr after 24 h. The maximum total yield of vincristine was 1.52-fold more than control in response to 100 µM Mj after one week. This increase was 2.16, 4.01, 2.39 and 1.97-fold for ajmalicine, vinblastine, vindoline and catharanthine respectively, in response to 100 µM Mj + 50 µM Cr. Mj + Cr can elevate alkaloid production by induction of <em>MAPK3</em> and <em>ORCA3</em> signaling pathway, which induces expression of downstream terpenoid indole alkaloids (TIAs) biosynthetic enzymes.