Abstract
Peanut (Arachis hypogaea L.) is one of the important oilseed crops of the Indian subcontinent and fungal diseases like early leaf spot (ELS) and late leaf spot (LLS) caused by Cercospora arachidicola and Phaeoisariopsis personata, respectively, are major peanut cultivation constraints. Defensins are basically antimicrobial peptides that have been implicated in plant defense against various microbial attacks. Transgenic peanut plants, developed through Agrobacterium mediated transformation of de-embryonated cotyledons and overexpressing a synthetic defensin fusion gene from fenugreek (Tfgd2) and radish (RsAFP2) linked by a linker peptide, were found to have enhanced resistance to the ELS and LLS infection over the wild type (cv. GG 20). Both transformed and untransformed lines were characterized for leaf spot diseases using a detached leaf assay. PCR and RT-PCR analyses confirmed stable integration and expression of these genes in peanut transgenics. This investigation provides further evidence that a fusion product of two plant defensins can be successfully implemented as a means of imparting resistance to multiple fungal pathogens through genetic engineering in peanut.
Highlights
Peanut (Arachis hypogaea L.), which is known as groundnut, is grown in around 109 countries between 40°N and 40°S, encompassing major regions of Asia and Africa (Shoba et al, 2012)
We have developed and characterized a transgenic peanut overexpressing a fusion gene made up of Tfgd2 and RsAFP2 defensins linked by a linker peptide sequence, for its resistance to early (ELS) and late leaf spot (LLS) diseases
Defensins are considered excellent candidates for transgenic approaches, and many defensins that can impart resistance when overexpressed in otherwise susceptible plants were identified (Gao et al, 2000; Jha and Chattoo, 2009; Portieles et al, 2010)
Summary
Peanut (Arachis hypogaea L.), which is known as groundnut, is grown in around 109 countries between 40°N and 40°S, encompassing major regions of Asia and Africa (Shoba et al, 2012). In the ongoing pursuit of disease resistant crops, defensins are one of the most extensively studied peptide families and are used as targets for transgenic approaches in a range of plant species (duPlessis, 2012). It was found that the defensin-encoding genes are overrepresented in some plants species, contributing around 3% of all genetic material in Arabidopsis (Silverstein et al, 2007) This accentuates the significance of these peptides in general plant biology, including plant defense (duPlessis, 2012). We have developed and characterized a transgenic peanut overexpressing a fusion gene made up of Tfgd and RsAFP2 defensins linked by a linker peptide sequence (occurring in the seeds of Impatiens balsamina), for its resistance to early (ELS) and late leaf spot (LLS) diseases
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