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ARS Home » Southeast Area » Mississippi State, Mississippi » Crop Science Research Laboratory » Corn Host Plant Resistance Research » Research » Publications at this Location » Publication #330332
Title: Expression profiling coupled with in-silico mapping identifes candidate genes for reducing aflatoxin accumulation in maize

Author
item DHAKAL, R. - LSU Agcenter
item CGAU, C. - LSU Agcenter
item KARAN, R. - University Of Florida
item Windham, Gary
item Williams, William
item SUBUDHU, P. - LSU Agcenter

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/22/2017
Publication Date: 4/6/2017
Citation: Dhakal, R., Cgau, C., Karan, R., Windham, G.L., Williams, W.P., Subudhu, P. 2017. Expression profiling coupled with in-silico mapping identifes candidate genes for reducing aflatoxin accumulation in maize. Frontiers in Plant Science. 8:503. https://doi.org/10.3389/fpls.2017.00503.
DOI: https://doi.org/10.3389/fpls.2017.00503

Interpretive Summary: Reducing Aspergillus flavus infection and aflatoxin accumulation in developing corn kernels through the identification and selection of resistance genotypes is an effective and sustainable control strategy. Introgression of multiple resistant QTL to susceptible, adaptive, and agronomically superior corn lines through marker assisted breeding will help in developing improved resistant lines. The characterization of various host defense mechanisms and associated resistance genes is necessary for developing resistant corn germplasm. Suppression subtraction hybridization (SSH) libraries were prepared from the developing kernels of corn inbred lines Mp715 (resistant inbred) and B73 (susceptible inbred) to identify differentially expressed genes (DEGs) in response to A. flavus inoculation. Three hundred DEGs were identified from SSH libraries and their expression was studied by reverse northern hybridization. Several genes related to plant stress response, signal transduction, and disease resistance were identified. Thirty DEGs potentially involved in aflatoxin resistance were used for transcript abundance in seven corn inbreds (Mp715, Mp719, Mp420, Mp313E, Mo18W, B73, and Va35) following fungal inoculations by using reverse transcription PCR (RT-PCR). Most genes were highly expressed in resistant inbreds compared to susceptible inbreds. Further validation of RT-PCR results using quantitative real-time PCR (qPCR) showed higher expression of pathogenesis-related protein-4 (PR-4), PR-5, and leucine rich repeat family protein among resistant germplasm most notably in Mp719. In-silico mapping identified 105 genes on or nearby QTL regions potentially involved in aflatoxin resistance. This integrated approach involving gene expression and QTL mapping led to the identification of several candidate genes most likely involved in host-plant resistance factors that suppress aflatoxin accumulation in corn.

Technical Abstract: Aflatoxin, a potent carcinogenic secondary metabolite produced by the fungus Aspergillus flavus, is hazardous to health of human and livestock when consumed in small amount. The lack of information about consistent QTL for aflatoxin resistance is a major obstacle in implementing marker assisted selection in order to develop aflatoxin resistant maize inbreds and hybrids. The characterization of various host defense mechanisms and associated resistance genes is necessary for developing resistant maize germplasms. Suppression subtraction hybridization (SSH) libraries were prepared from the developing kernels of inoculated Mp715 (resistant inbred) and B73 (susceptible inbred) to identify differentially expressed genes (DEGs) in response to A. flavus inoculation. Three hundred DEGs were identified from SSH libraries and their expression was studied by reverse northern hybridization. Several genes (including transcription factors) related to stress response, signal transduction, and disease resistance were identified. Thirty DEGs potentially involved in aflatoxin resistance were used for transcript abundance in seven inbreds (Mp715, Mp719, Mp420, Mp313E, Mo18W, B73, and Va35) at different time points after inoculation by using reverse transcription PCR (RT-PCR). Most genes were highly expressed in resistant inbreds compared to susceptible inbreds. Further validation of RT-PCR results using quantitative real-time PCR (qPCR) showed higher expression of pathogenesis-related protein-4 (PR-4), PR-5, and leucine rich repeat family protein among resistant germplasm most notably in Mp719. In-silico mapping identified 105 genes on or nearby QTL regions potentially involved in aflatoxin resistance. This integrated approach involving gene expression and QTL mapping led to the identification of several candidate genes most likely involved in host-plant resistance and host-pathogen interaction leading to reduced aflatoxin accumulation in maize.