Analysis of plant expression profiles revealed that aphid attack triggered dynamic defense responses in sorghum plant

Authors: Huang, Yinghua; HUANG, JIAN - Oklahoma State University

Submitted to: Frontiers in Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/27/2023
Publication Date: 8/15/2023
Citation: Huang, Y., Huang, J. 2023. Analysis of plant expression profiles revealed that aphid attack triggered dynamic defense responses in sorghum plant. Frontiers in Genetics. 14. Article 1194273. https://doi.org/10.3389/fgene.2023.1194273.
DOI: https://doi.org/10.3389/fgene.2023.1194273

Interpretive Summary: Aphids are the most important insect pests of small grains in the U.S. and worldwide. Sorghum plants are often attacked by greenbug and sugarcane aphids, resulting in significant crop damage and yield loss. Although few sorghum sources with natural resistance to greenbug have been identified, little is known about the genetic mechanisms at the molecular level. In this study, our primary goal was to investigate defense genes functioning in resistant sorghum plants to protect themselves from aphid feeding. Thus, the genome-wide expression profiles induced by greenbug were developed and subsequently assessment of those differentially expressed genes was conducted using the genomics approach. Our results from those analyses revealed that molecular responses of host plants to phloem-feeding of greenbugs were comprehensive and dynamic changes (i.e., up- and down-regulation) of gene expression in infested plants in response to greenbug feeding. The rapid reaction of the host defense brought up immediate activation of the signal transduction pathways and subsequent expression of resistance genes to defend against the attackers. Furthermore, comparative analysis of the greenbug-induced transcript profiles in resistant plants with those in susceptible cultivars provided new insight into the defense mechanisms protecting crop plants from attack by these damaging cereal aphids. The improved understanding of the molecular details of host-aphid interaction and the genetic mechanisms underlying host plant defense can not only advance our knowledge on the basics of plant performance but also help us design new strategies for better managing aphid pests.

Technical Abstract: Sorghum [Sorghum bicolor (L.) Moench] is one of the most important cereal crops grown worldwide but is often attacked by aphids such as greenbug and sugarcane aphid. The greenbug (Schizaphis graminum Rondani) has been a major aphid pest of sorghum as well other small grains. In response to aphid attack, host plant initiates a large transcriptional reorganization, leading to activation of the host defense genes in infested plants. In this study, transcriptional profiles were developed from two pools of sorghum seedling tissues representing aphid-infested and non-infested sorghum seedlings, respectively using microarray and RNA-seq methodss. Then transcriptome analysis revealed a wide range of gene activities in aphid-challenged seedlings of the resistant genotype (PI 550607) when compared to the same genotype without infestation prepared in parallel. Sequence annotation and functional analysis showed that many differentially expressed genes were related to direct host defense or signal transduction pathways which regulate host defense. In addition to the common responsive genes, defense-related transcripts were expressed to respond to greenbug specifically. These unique transcripts expressed exclusively in the resistant genotype challenged by aphid, but not in the transcript profiles obtained either from other resistant or susceptible sorghum cultivars infested by greenbug. Thus, the differential expression data indicate that aphid triggered dynamic defense responses in sorghum plants and furthermore suggest that the genotype-specific defense response to aphids is a complex process involving both general defense systems and specific resistance mechanisms. Finally, the results of this study provide new insights into the mechanisms underlying host plant defense against aphids and help us design better strategies for effectively controlling aphid pests.