Submitted to: PLoS One
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/4/2013
Publication Date: 10/16/2013
Publication URL: http://handle.nal.usda.gov/10113/59033
Citation: Goyal, R.K., Hancock, R.E., Mattoo, A.K., Misra, S. 2013. Expression of an engineered heterologous antimicrobial peptide in potato alters plant development and mitigates normal abiotic and biotic responses. PLoS One. 8(10):e77505. DOI: 10.1371/journal.pone.0077505. Interpretive Summary: Sustained plant losses due to microbial diseases cause crop yield reduction and are of major economic concern to farmers and the agriculture industry. Throughout the world there is an ongoing effort to develop crops resistant to different diseases. Diseases and pests cause major losses in total potato production, conservative estimates putting annual losses at 22% worldwide. Plants use different defense strategies against pathogens (bacteria, fungi and viruses) including the less known production of antimicrobial peptides (AMPs) that have a wide distribution in nature from microorganisms to complex eukaryotes. Transgenic research has demonstrated that when heterologous antimicrobial peptide variants, synthetic AMPs, or other plant AMPs are introduced into plants, including potato, they bring about broad-spectrum resistance to diverse types of pathogens. In collaboration with two institutions in Canada, the USDA scientist tested two transgenic potato lines that expressed an AMP called msrA3 side by side with the control wild type plants for their response to abiotic stresses (induced senescence, oxidative stress and wounding) as well as to a potato pathogen (Fusarium solani). This team demonstrated in this publication that expression of MsrA3 in potato provided resistance against the pathogen F. solani, mitigated plant defense responses, and altered timing of bud development, which culminated in increased yield by the two transgenic potato lines. This research is of interest to breeders, plant physiologists, pathologists and industry.
Technical Abstract: Antimicrobial cationic peptides (AMPs) are ubiquitous small proteins used by living cells to defend against a wide spectrum of pathogens. Their amphipathic property helps their interaction with negatively charged cellular membrane of the pathogen causing cell lysis and death. AMPs also modulate signaling pathway(s) and cellular processes in animal models; however, little is known of cellular processes other than the pathogen-lysis phenomenon modulated by AMPs in plants. An engineered heterologous AMP, msrA3, expressed in potato was previously shown to cause resistance of the transgenic plants against selected fungal and bacterial pathogens. These lines together with the wild type were studied for growth habits, and for inducible defense responses during challenge with biotic (necrotroph Fusarium solani) and abiotic stressors (dark-induced senescence, wounding and temperature stress). msrA3-expression not only conferred protection against F. solani but also delayed development of floral buds and prolonged vegetative phase. Analysis of select gene transcript profiles showed that the transgenic potato plants were suppressed in the hypersensitive (HR) and reactive oxygen species (ROS) responses to both biotic and abiotic stressors. Also, the transgenic leaves accumulated lesser amounts of the defense hormone jasmonic acid upon wounding with only a slight change in salicylic acid as compared to the wild type. Thus, normal host defense responses to the pathogen and abiotic stressors were mitigated by msrA3 expression suggesting MSRA3 regulates a common step(s) of these response pathways. The stemming of the pathogen growth and mitigating stress response pathways likely contributes to resource reallocation for higher tuber yield.