Submitted to: Planta
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/28/2005
Publication Date: 11/15/2005
Citation: Park, S., Huang, Y., Ayoubi, P. 2005. Identification of expression profiles of sorghum genes in response to greenbug phloem-feeding using cDNA substraction and microarray analysis. Planta. 223:932-947. Interpretive Summary: cDNA microarrays are a powerful technology to analyze gene activity changes in plants that are exposed to various biotic and abiotic stresses or undergoes the switch of developmental phases. In this study, we collected plant tissues from a greenbug resistant plant before and during greenbug infestation, and examined gene expression changes in the sorghum seedlings in response to greenbug attack using microarray technology. Comparison of the gene expression profiles in the parallel assays revealed distinct expression patterns in these test materials, suggesting that greenbug infestation induced dramatic changes of gene expression in infested sorghum cells/tissues to activate the signal transduction pathways and to produce direct resistance factors for their defensive actions. Identification and molecular characterization of these differentially expressed genes will contribute to a better understanding of the genetic interactions underlying host defense responses and this set of aphid-responsive genes may be an important source for developing improved resistance to greenbug pests in sorghum as well as in other cereal crops.
Technical Abstract: Interaction between phloem-feeding aphids and host plants depends upon a unique stylet penetration pathway and is indeed very complex. Understanding the molecular details of this interaction, such as the aphid genes required for infestation, host genes needed for defense responses, and the genetic mechanisms by which host and insect signaling networks are regulated, can help us design new strategies for better managing aphid pests. As an initial step of our functional genomics project on molecular interactions of aphids-crop plants, we selected grain sorghum [Sorghum bicolor (L.) Moench] and greenbug [Schizaphis graminum (Rondani)] as a model system to conduct the genome-wide analysis of host gene activities in response to greenbug attack using gene expression profiling. In this study, cDNA microarray technology showed a large scale of gene activation in infested sorghum seedlings of a resistant genotype when compared to the same genotype without infestation as prepared in parallel. Overall, approximately 12.6% of the 2,304 SSH sequences spotted on the microarray chip showed more than 2-fold stronger signals, of which many differentially expressed genes are related to direct or indirect host defense. In general, more genes were induced to express at significant high levels; whereas a small number of genes were suppressed by greenbug feeding. Comparison of transcript profiles reveals overlapping activation of defense related genes, suggesting that host responses to insects and pathogens are linked in some cases. Finally, this study demonstrates that the microarray technology is already showing new features of plant responses to insect attack. And genome-wide transcriptional profiling is particularly appropriate for the study of molecular interactions of plant-aphid and is providing novel insight into the pathways involved and their interactions with one another.