MICRORNA REGULATION OF HOST PLANT RESISTANCE TO APHIDS

Aphids are very common insect pests that feed on plants by inserting their highly-modified mouthparts directly into plant vascular tissues to feed on the sugars and amino acids that are transported in the phloem sap. Aphids damage crops by transmitting viruses, altering normal plant functions, and removing nutrients. They are highly adaptable, and their high reproductive rates makes them particularly difficult to control. The heavy and persistent use of insecticides has resulted in the evolution of resistance to many insecticides, making the use of non-chemical alternatives for controlling these pests, including host plant resistance, increasingly important. Aphid resistant traits have been identified in a number of crop systems and some of these have entered breeding programs and have been released to the field. In most cases, however, little is known about the molecular basis for this resistance. A better understanding of the genes, regulatory pathways, and mechanisms that contribute to resistance would assist plant breeding programs in developing long-lasting aphid resistance. Studies are now revealing gene expression patterns and defense pathways that are differentially regulated in response to aphid infestation in susceptible and resistant plants. What is now required is more information on the regulation of these responses. Research in the last several years has established that small non-coding RNAs function as critical regulators of plant development and plant responses to environmental stresses by silencing (turning off) genes. Small RNAs have been identified in phloem sap; the phloem sap is used by aphids as their sole food source. This project will determine if specific small RNAs regulate gene expression in response to the stress caused by aphid feeding as components of the resistance mechanism, possibly playing direct roles as plant defense molecules. The goal of the work outlined in this project is to identify small RNAs and their targets that are involved in aphid-host plant interactions and to establish their role in host plant resistance.