Submitted to: Journal of Toxicology Toxins Reviews
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/24/2005
Publication Date: 9/18/2005
Citation: Guo, B., Holbrook, Jr., C. C., Yu, J., Lee, R. D., Lynch, R. E. 2005. Application of technology of gene expression in response to drought stress and elimination of preharvest aflatoxin contamination. In: Abbas, H. (ed.). Aflatoxin and Food Safety. Boca Raton, Florida: CRC Press. Pp. 313-331. Interpretive Summary: In the field, corn and peanut become contaminated with aflatoxins when subjected to prolonged periods of heat and drought stress, especially in the Southern U.S. To meet the challenge of prevention of preharvest aflatoxin contamination, it will be necessary to have a more detailed understanding of the organization and function of the genetic material of corn and peanut in response to drought stress and other factors. The genes that control functions leading to plant reaction to the environmental stress and fungal infection must be identified. This article reviews drought stress and aflatoxin contamination, new molecular tools used to study gene expression, and genetic engineering approaches to control aflatoxin contamination. Drought tolerance, for example, may be determined by many genetic factors. The "one-gene-at-a-time" approach for analyzing gene function is inadequate. It is now possible to study global gene expressions in a specific tissue and at a specific time, and to locate multiple genes of plants in responding to environmental stresses. There are several major new molecular tools used for gene functional analysis, such as Expressed Sequence Tag (EST) and Microarray technology. Research progress has been made in our laboratories using microarray chip to study gene expression for gene identification and characterization.
Technical Abstract: Aflatoxin contamination in the field is known to be influenced by numerous factors. Drought and high temperatures are conducive to Aspergillus flavus infection and aflatoxin contamination. This article reviews the application of new molecular tools to study host plant resistance to biotic and abiotic factors affecting preharvest aflatoxin contamination in corn and peanut. We will also summarize recent studies conducted in our laboratories to evaluate the relationship of drought tolerance and aflatoxin contamination, and discuss the progress in using genetic engineering approaches to control preharvest aflatoxin contamination. The application of molecular tools, such as proteomics, DD-RT-PCR (differential display reverse transcription-polymerase chain reaction), expressed sequence tag (EST) and gene chip technology (macro/micro-array) to study gene expression in response to drought stress, and genetic transformation, will be reviewed. We have used DD-RT-PCR to display genes expressed in peanut and corn grown under drought stressed vs irrigated condition. Microarray technology has been used to study the whole genome as influenced by drought stress and fungal infection in corn and peanut. We are also studying A. flavus ESTs to better understand the genetic control and regulation of toxin biosynthesis. Because of the complexity of the Aspergillus-plant (corn and peanut) interactions, better understanding of the genetic mechanisms of resistance will be needed using both conventional and molecular breeding for crop improvement and control of preharvest aflatoxin contamination. Genetic improvement of crop resistance to drought stress is one component and will provide a good perspective on the efficacy of control strategy through genetic improvement.