In Silico Identification of Mimicking Molecules as Defense Inducers Triggering Jasmonic Acid Mediated Immunity against Alternaria Blight Disease in Brassica Species.

Rajesh K Pathak,Mamta Baunthiyal,Gohar Taj,Rohit Shukla,Dinesh Pandey,Anil Kumar

doi:10.3389/fpls.2017.00609

Abstract

Alternaria brassicae and Alternaria brassicicola are two major phytopathogenic fungi which cause Alternaria blight, a recalcitrant disease on Brassica crops throughout the world, which is highly destructive and responsible for significant yield losses. Since no resistant source is available against Alternaria blight, therefore, efforts have been made in the present study to identify defense inducer molecules which can induce jasmonic acid (JA) mediated defense against the disease. It is believed that JA triggered defense response will prevent necrotrophic mode of colonization of Alternaria brassicae fungus. The JA receptor, COI1 is one of the potential targets for triggering JA mediated immunity through interaction with JA signal. In the present study, few mimicking compounds more efficient than naturally occurring JA in terms of interaction with COI1 were identified through virtual screening and molecular dynamics simulation studies. A high quality structural model of COI1 was developed using the protein sequence of Brassica rapa. This was followed by virtual screening of 767 analogs of JA from ZINC database for interaction with COI1. Two analogs viz. ZINC27640214 and ZINC43772052 showed more binding affinity with COI1 as compared to naturally occurring JA. Molecular dynamics simulation of COI1 and COI1-JA complex, as well as best screened interacting structural analogs of JA with COI1 was done for 50 ns to validate the stability of system. It was found that ZINC27640214 possesses efficient, stable, and good cell permeability properties. Based on the obtained results and its physicochemical properties, it is capable of mimicking JA signaling and may be used as defense inducers for triggering JA mediated resistance against Alternaria blight, only after further validation through field trials.

Highlights

Brassica species are one of the second largest oilseed producing crops in the world after soybean [Glycine max (L.) Merr.], surpassing sunflower (Helianthus annuus L.), peanut (Arachis hypogaea L.), and cottonseed (Gossypium hirsutum L.) during the last several decades (FAO, 2010; Agricultural Outlook, 2010–2019)
The publically accessible complete nucleotide sequence of the COI1 (2327 bp) from B. rapa L., which is expected to play vital role in defense responses during pathogenesis of Alternaria blight, was downloaded from NCBI and subjected to MATLAB Bioinformatics toolbox2 to visualize the distribution of nucleotide using pie chart (Figure 1A) and dimmers were displayed in bar chart (Figure 1B)
After determining the content of amino acid present in the protein sequence of COI1, we have found the high content of Leucine, Arginine, Glutamic acid and Valine, and this information was plotted using bar graph (Figure 1D)

Summary

Introduction

Brassica species are one of the second largest oilseed producing crops in the world after soybean [Glycine max (L.) Merr.], surpassing sunflower (Helianthus annuus L.), peanut (Arachis hypogaea L.), and cottonseed (Gossypium hirsutum L.) during the last several decades (FAO, 2010; Agricultural Outlook, 2010–2019). More than 30 diseases are known to occur on Brassica crops in India (Saharan, 1992), majority of which are caused by different fungal pathogens, whereas viral and bacterial diseases have minute effect on their yield. Alternaria blight caused by Alternaria brassicae and Alternaria brassicicola is the most common and destructive disease of Brassica throughout the world which can result in yield reductions of up to 36% (Duczek et al, 1998). Many efforts have been made by scientists to develop disease resistant transgenic plants with limited success to develop complete de novo resistance against Alternaria blight due to lack of knowledge about the resistance gene homologs (Mondal et al, 2003; Taj et al, 2004; Marmath et al, 2011; Kumar et al, 2014). There is required use of innovative approaches in agricultural sciences to tackle such type of problems

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