|KRONMILLER, BRENT - Oregon State University|
|RHODES, ADELAIDE - Oregon State University|
Submitted to: BMC Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/25/2019
Publication Date: 5/28/2019
Citation: Dombrowski, J.E., Kronmiller, B.A., Hollenbeck, V.G., Rhodes, A., Henning, J.A., Martin, R.C. 2019. Transcriptome analysis of the model grass Lolium temulentum exposed to green leaf volatiles. Biomed Central (BMC) Plant Biology. 19:222. https://doi.org/10.1186/s12870-019-1799-6.
Interpretive Summary: Grasses are routinely cut and grazed upon throughout their life cycle. Previously it has been shown that grass plants exposed to chemicals released from cut/damaged grasses, known as green leaf volatiles (GLV), rapidly activated specific biochemical signals 3 minutes after exposure. Since GLV are released during wounding, we wanted to investigate what genes and signaling pathways would be induced in undamaged plants exposed to GLV. Sequencing of gene expression libraries generated from grass plants exposed to GLV identified 4308 up- and 2794 down-regulated genes. Analysis of these sequences revealed genes known for signaling, response to stimulus and stress, with sequences identified that are involved in the biosynthesis of stress hormones, and proteins for growth and stress related pathways. Detailed expression analyses of selected genes showed a direct correlation between their activation by GLV and wounding. These results coupled with previously collected data indicated that volatile compounds released from damaged plants (not only grasses) transiently prime the grass’ response for the potential oncoming wound stress, and may have a dual role for inter- as well as intra-plant signaling. These identified gene sequences provide a valuable molecular resource that will be used to develop approaches that can improve the recovery, regrowth and long-term fitness of forage and turf grasses before/after cutting or grazing.
Technical Abstract: Forage and turf grasses are routinely cut and grazed upon throughout their life cycle. When grasses are cut or damaged, they rapidly release a volatile chemical cocktail called green leaf volatiles (GLV). Previously we have shown that mechanical wounding or exposure to GLV released from cut grass, activated a Lt 46 kDa mitogen-activated protein kinase (MAPK) within 3 minutes and a 44 kDa MAPK within 15-20 minutes in the model grass species Lolium temulentum (Lt). Currently very little is known concerning the perception, signaling or molecular responses associated with wound stress in grasses. Since GLV are released during wounding, we wanted to investigate what genes and signaling pathways would be induced in undamaged plants exposed to GLV. RNA-Seq generated transcriptome of Lolium plants exposed to GLV identified 4308 up- and 2794 down- down-regulated distinct differentially expressed sequences (DES). Gene Ontology analysis revealed a strong emphasis on signaling, response to stimulus and stress related categories. Transcription factors and kinases comprise over 13% of the total DES found in the up-regulated database. The analysis showed a strong initial burst within the first hour of GLV exposure with over 60% of the up-regulated DES being induced. Specifically sequences annotated for enzymes involved in the biosynthesis of jasmonic acid and other plant hormones, mitogen-activated protein kinases and WRKY transcription factors were identified. Interestingly, eleven DES for ferric reductase oxidase, an enzyme involve in iron uptake and transport, were exclusively found in the down-regulated database. Twelve DES of interest were selected for qRT-PCR analysis, all displayed a rapid induction one hour after GLV exposure and were also strongly induced by mechanical wounding. The information gained from the analysis of this transcriptome and previous studies indicated that GLV released from cut grasses transiently primes an undamaged plants’ wound stress pathways for potential oncoming damage, and may have a dual role for inter- as well as intra-plant signaling.