Proteomic analysis of elicitation of downy mildew disease resistance in pearl millet by seed priming with β-aminobutyric acid and Pseudomonas fluorescens.
Downy mildew is one of the severe diseases of pearl millet, globally affecting its commercial production. Priming of seeds of a susceptible cultivar of pearl millet with β-aminobutyric acid (BABA) and Pseudomonas fluorescens has reduced the downy mildew disease incidence level under field studies. In the current study, proteomic approach was used to elucidate the poorly studied resistance mechanism in these elicitor primed pearl millet seeds in response to Sclerospora graminicola infection. 2DE-MS/MS based proteomic approach revealed that majority of the 63 differentially accumulated (p≤0.05) proteins associated with energy and metabolism followed by stress and defense category. Multivariate statistics disclosed that infection caused by the pathogen rather than elicitor treatment had a major influence on the dynamics of protein abundance. Mechanism of priming mediated by BABA and P. fluorescens were different from each other as evident by the protein abundance profile of hierarchical clustering analysis. Over-representation of proteins pertaining to glucose metabolism suggests that seed priming ensures plant protection against disease without compromising its normal growth and development. In addition the study forms a basis for future investigation by functional analysis of these differentially accumulated proteins to further unravel the resistance mechanism of elicitor primed plant against the S. graminicola.


CONCLUSIONS
The study is based on the comparative proteomic analysis between BABA and P. fluorescens mediated resistance in pearl millet, in response to downy mildew causing biotroph - S. graminicola. To our knowledge, this article is the first to report on seedling proteome of pearl millet whose genome is not yet sequenced. In addition, the study also provides clue for the plausible antagonistic cross-talk that might exist between jasmonic acid signaling and salicylic acid signaling in SAR and ISR mediated resistance by BABA and P. fluorescens against the downy mildew pathogen. Furthermore, pearl millet seedling proteome being perturbed by pathogen inoculation was more apparent than that caused by elicitor treatment, as revealed by multivariate statistics like PCA. Analysis by gene enrichment tools further revealed that the glucose metabolism pathway was majorly being affected in our study. This could be attributed to the essential balance that is being maintained in energy diversion towards stress and normal physiological process due to the priming effect of the elicitors against biotic stress.
Department of Studies in Biotechnology, Manasagangotri, University of Mysore, Mysore 570 006, Karnataka, India.
Chandra Pal
CP
Anup
Department of Studies in Biotechnology, Manasagangotri, University of Mysore, Mysore 570 006, Karnataka, India.
Prasad
P
Melvin
Department of Studies in Biotechnology, Manasagangotri, University of Mysore, Mysore 570 006, Karnataka, India.
Nataraj
N
Shilpa
HR-LCMS Lab Sophisticated Analytical Instrumentation Facility, Indian Institute of Technology, Bombay, India.
Mayuri Nalin
MN
Gandhi
HR-LCMS Lab Sophisticated Analytical Instrumentation Facility, Indian Institute of Technology, Bombay, India.
Manali
M
Jadhav
Camo Software, Bangalore, India.
Hussain
H
Ali
Department of Studies in Biotechnology, Manasagangotri, University of Mysore, Mysore 570 006, Karnataka, India. Electronic address: krk@appbot.uni-mysore.ac.in.
Kukkundoor Ramachandra
KR
Kini
D000613:Aminobutyrates / Q000494:pharmacology*; D000935:Antifungal Agents / Q000494:pharmacology; D004194:Disease; D060467:Disease Resistance / Q000187:drug effects / Q000502:physiology; D031782:Pennisetum / Q000187:drug effects / Q000378:metabolism* / Q000382:microbiology*; D044742:Peronospora / Q000502:physiology; D010935:Plant Diseases / Q000382:microbiology* / Q000517:prevention & control*; D011551:Pseudomonas fluorescens / Q000502:physiology*; D012639:Seeds / Q000187:drug effects / Q000378:metabolism / Q000382:microbiology
D000613:Aminobutyrates; D000935:Antifungal Agents; C012223:alpha-aminobutyric acid
Pearl millet; Priming; Proteomics; S. graminicola; β-aminobutyric acid (BABA) and P. fluorescens