Submitted to: Plant Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/3/2006
Publication Date: 2/21/2006
Citation: Mozoruk, J.J., Hunnicutt, L.E. , Cave, R.D., Hunter, W.B., Bausher, M.G. 2006. Profiling transcriptional changes in Citrus sinensis (L.) Osbeck challenged by herbivory from the xylem-feeding leafhopper Homalodisca coagulata (Say) by cDNA macroarray analysis. Plant Science. 170: 1068-1080. Interpretive Summary: Herbivorous insects cause extensive damage to many agriculturally important crops by way of physical damage or transmission of plant pathogens. Control of these destructive pests has traditionally relied on chemical pesticides; however, this control method is often costly and generally results in a negative impact to the environment. This has warranted the pursuit of more environmentally-friendly and cost-effective control methods to combat economically destructive pest insects. One such method is to augment or increase the effectiveness of the host plant’s own defensive mechanisms. The research presented here aims to decipher and understand the molecular mechanisms of defense by studying its underlying genetic basis.
Technical Abstract: The molecular mechanisms underlying plant defense to sap-feeding insects are slowly being uncovered. In large part, past research has focused on interactions between phloem-feeding insects and their annual host plants with little emphasis on xylem-feeders or woody perennials—especially fruit trees. Using nylon filter cDNA arrays, we analyzed the transcriptional changes of 1731 non-redundant citrus transcripts that resulted from herbivory by a xylem-feeding leafhopper, the glassy-winged sharpshooter (GWSS), Homalodisca coagulata (Say) (Hemiptera: Cicadellidae). In addition, herbivory-elicited changes were compared to those of mechanical damage to better identify GWSS-specific responses. GWSS feeding led to a significant expression change in 50 transcripts. Of these, 14 were also changed by mechanical damage; however, the magnitude was in many cases reduced, suggesting transcriptional modification by GWSS-derived elicitors. Sequence similarity searches with the public database GenBank indicated that the responsive transcripts broadly function in direct defense, defense signaling, ROS scavenging, transport, cell wall modification, photosynthesis and abiotic stress. In particular, GWSS feeding resulted in a transcript profile that resembled wounding, likely through jasmonic acid-independent pathways as well as an association with dehydration stress. In contrast to similar studies with aphids, salicylic acid-dependent pathogenesis–related genes were weakly induced. Interestingly, six of the GWSS-responsive transcripts failed to significantly match any public protein sequence signifying their potential as novel genes functioning in plant defense, wound response or abiotic stress.