Abstract
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 (MAPK3), a transcription factor (TF) known as octadecanoid-responsive Catharanthus AP2-domain 3 (ORCA3) upstream of plant alkaloids biosynthetic pathway. Maximum expression levels of peroxidase1 (PRX1), geissoschizine synthase (GS) (24 h-treatment), MAPK3 and ORCA3 (8 h-treatment), 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 (STR) 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 MAPK3 and ORCA3 signaling pathway, which induces expression of downstream terpenoid indole alkaloids (TIAs) biosynthetic enzymes.
Highlights
Catharanthus roseus L. (Apocynaceae) is a significant pharmaceutical plant that contains more than 130 alkaloids named terpenoid indole alkaloids (TIAs), 25 of which are found in nature in dimeric form and have antidiabetic, bactericide, antihypertensive, and anticancerous activities
As it was considered before, the low levels of dimeric anticancer drugs, their costliness, and their difficult chemical biosynthesis have attracted the attention of many researchers and prompted them to find ways to optimize the production of these TIAs
The current results showed that there was an upregulation of octadecanoid-responsive Catharanthus AP2domain 3 (ORCA3) and mitogenactivated protein kinase 3 (MAPK3) in response to Methyl jasmonate (Mj) alone and in combination with Cr treatments, in consistent with Gao et al (2010) reporting that transcription of ORCA3 and orthologs of MAPK3 in other plants were upregulated by Mj treatment and different stresses like high salinity, cold, heat, wounding, chitin, UV, osmotic, and oxidative stresses
Summary
Catharanthus roseus L. (Apocynaceae) is a significant pharmaceutical plant that contains more than 130 alkaloids named terpenoid indole alkaloids (TIAs), 25 of which are found in nature in dimeric form and have antidiabetic, bactericide, antihypertensive, and anticancerous activities. (Apocynaceae) is a significant pharmaceutical plant that contains more than 130 alkaloids named terpenoid indole alkaloids (TIAs), 25 of which are found in nature in dimeric form and have antidiabetic, bactericide, antihypertensive, and anticancerous activities. C. roseus is the source of ajmalicine which has been identified as an antihypertensive agent (Ncube & Van Staden, 2015). The pharmacological significance of TIAs and their low amounts in the plant which is the unique source of them (around 0.0005 % of dry mass) have motivated broad research on the TIA pathway for manipulating plant metabolism to enhance alkaloid amounts. One important technique for raising secondary metabolite contents is the utilization of heavy metals in plant cell, tissue, and organ cultures to enhance the generation of secondary metabolites, and to promote the de novo biosynthesis of them (Wójciak-Kosior et al, 2016). The effects of Cr combined with Mj on the expression levels of key elements of the biosynthetic pathway, such as strictosidine synthase (STR), deacetylvindoline-4-Oacetyltransferase (DAT), geissoschizine synthase (GS) and a peroxidase (PRX1), has not yet been determined
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