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Research Project: Genetic Mechanisms and Improvement of Insect Resistance in Wheat, Barley, and Sorghum

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Title: Genome-wide characterization of the sorghum JAZ gene family and their responses to phytohormone treatments and aphid infestation

item SHRESTHA, KUMAR - Oklahoma State University
item Huang, Yinghua

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/3/2022
Publication Date: 2/25/2022
Citation: Shrestha, K., Huang, Y. 2022. Genome-wide characterization of the sorghum JAZ gene family and their responses to phytohormone treatments and aphid infestation. Scientific Reports. 12. Article 3238.

Interpretive Summary: Jasmonate ZIM-domain (JAZ) proteins are important as they are involved in many physiological and stress-related processes in plants. Sorghum is not only an important cereal crop but also a preferred bioenergy plant. Although many JAZ protein genes have been well characterized in the model plant species, little is known about the organization and function of JAZ genes in sorghum plants. Thus, ARS scientists in Stillwater, Oklahoma have recently conducted the genome-wide analysis of JAZ gene family in sorghum. Here, they report that a total of 18 JAZ genes were discovered in the sorghum genome and evidently those newly identified sorghum JAZ genes were found to share the similar structural features that were reported in the JAZ genes in other plant species. During this study, the scientists have also conducted molecular experiments to investigate the function of those JAZ genes using quantitative real-time PCR. The results generated from the experiments showed differential expression of the 18 JAZ genes in response to attack by sugarcane aphid, a devastating insect pest on sorghum. Similarly, differential expression patterns were also observed in sorghum plants treated with certain plant hormones that are usually involved in plant-insect interactions. Of the 18 sorghum JAZ genes, four genes (namely SbJAZ1, SbJAZ5, SbJAZ13 and SbJAZ16) were highly expressed in resistant plant in response to aphid infestation, suggesting their roles in host plant defense against aphid attack. In summary, the resulted information from this study will contribute not only to the JAZ genes as a useful tool for crop improvement but also to a better understanding of the molecular mechanisms of plant resistance to sugarcane aphids.

Technical Abstract: Jasmonate ZIM-domain (JAZ) proteins are the key repressors of the jasmonic acid (JA) signal transduction pathway and play a crucial role in stress-related defense, phytohormone crosstalk and modulation of the growth-defense tradeoff. In this study, the sorghum genome was analyzed through genome-wide comparison and domain scan analysis, which led to the identification of 18 sorghum JAZ (SbJAZ) genes. All SbJAZ proteins possess the conserved TIFY and Jas domains and they formed a phylogenetic tree with five clusters related to the orthologs of other plant species. Similarly, evolutionary analysis indicated the duplication events as a major force of expansion of the SbJAZ genes and there was strong neutral and purifying selection going on. In silico analysis of the promoter region of the SbJAZ genes indicates that SbJAZ5, SbJAZ6, SbJAZ13, SbJAZ16 and SbJAZ17 are rich in stress-related cis-elements. In addition, expression profiling of the SbJAZ genes in response to phytohormones treatment (JA, ET, ABA, GA) and sugarcane aphid (SCA) was performed in two recombinant inbred lines (RILs) of sorghum, resistant (RIL 521) and susceptible (RIL 609) to SCA. Taken together, data generated from phytohormone expression and in silico analysis suggests the putative role of SbJAZ9 in JA-ABA crosstalk and SbJAZ16 in JA-ABA and JA-GA crosstalk to regulate certain physiological processes. Notably, upregulation of SbJAZ1, SbJAZ5, SbJAZ13 and SbJAZ16 in resistant RIL during JA treatment and SCA infestation suggests putative functions in stress-related defense and to balance the plant defense to promote growth. Overall, this report provides valuable insight into the organization and functional characterization of the sorghum JAZ gene family.