Transgenic mimicry of pathogen attack stimulates growth and secondary metabolite accumulation

Abstract

Plant secondary metabolites, including pharmaceuticals, flavorings and aromas, are often produced in response to stress. We used chemical inducers of the pathogen defense response (jasmonic acid, salicylate, killed fungi, oligosaccharides and the fungal elicitor protein, cryptogein) to increase metabolite and biomass production in transformed root cultures of the medicinal plant, Withania somnifera, and the weed, Convolvulus sepium. In an effort to genetically mimic the observed effects of cryptogein, we employed Agrobacterium rhizogenes to insert a synthetic gene encoding cryptogein into the roots of C. sepium, W. somnifera and Tylophora tanakae. This genetic transformation was associated with stimulation in both secondary metabolite production and growth in the first two species, and in growth in the third. In whole plants of Convolvulus arvensis and Arabidopsis thaliana, transformation with the cryptogein gene led, respectively, to increases in the calystegines and certain flavonoids. A similar transgenic mimicry of pathogen attack was previously employed to stimulate resistance to the pathogen and abiotic stress. In the present study of biochemical phenotype, we show that transgenic mimicry is correlated with increased secondary metabolite production in transformed root cultures and whole plants. We propose that natural transformation with genes encoding the production of microbial elicitors could influence interactions between plants and other organisms.

Metabolic shift from withasteroid formation to phenylpropanoid accumulation in cryptogein-cotransformed hairy roots of Withania somnifera (L.) Dunal

“…A synthetic β-cryptogein gene was constructed to study the pathogen-induced molecular interactions in plants for initiation of the defense response, mediated by elicitin (O'Donohue et al 1995). Genetic (endogenous) expression of the β-cryptogein protein was shown to mimic the effects of exogenous cryptogein treatment on growth and secondary metabolite accumulation (Chaudhuri et al 2009). Through transfer of cryptogein gene in target plants, earlier studies aimed either to improve secondary metabolite production in transformed plants and cotransformed hairy root cultures, such as Tylophora tanachae, Bacopa monnieri, and Coleus blumei (Chaudhuri et al 2009;Majumdar et al 2012;Vuković et al 2013), or to achieve the resistance against plant pathogens in Arabidopsis thaliana and N. tabacum (Tepfer et al 1998;O'Donohue et al 1995).…”

A Proteomic Approach to Evaluate the Effects of Endogenous Expression of Cryptogein Gene in Crypt-Transgenic Plants of Bacopa monnieri

“…Cryptogein (crypt)-induced elicitation, as established in transgenic plants expressing crypt gene showed enhanced accumulation of secondary metabolites in many plant species [7,9,30], including B. monnieri [19,20] In the present study, we compared the whole leaf proteome using 2DGE to understand the cross-talks between different plant defence systems that ultimately promoted bacosides (triterpenoid saponins) biosynthesis in crypt-transgenic plant lines as evident in our previous study [20]. Using a broad pH range IPG strip (pH 3-11) 54 differentially abundant proteins were identified and function of 85 % of these differentially abundant proteins could be identified in the present study.…”

“…Over expression of β-cryptogein induces HR in tobacco and triggers resistance against P. parasitica var nicotianae [5,6] and other pathogens. Effective increase in biomass and/ or secondary metabolites accumulation in crypt-transgenic cultures in a number of plant species have also been observed [7][8][9], where the crypt gene was either under the constitutive promoter [7] or under the inducible promoter [8]. …”

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“…Medicinal plants are important source of bioactive compounds, which are used as pharmaceuticals, agrochemicals, fragrance ingredients and food additives, medicinal and other dietary supplements [1]. Out of nearly 50 members of the family Asclepiadaceae, which are well distributed over Africa, Asia, Australia and the Pacific Islands, only 23 have been reported to contain phenanthroindolizidine alkaloids and among these most of the alkaloids have been obtained from Tylophora indica [2].…”