Transcriptome analysis of wounding in the model grass Lolium temulentum

Authors: Dombrowski, James; KRONMILLER, BRENT - Oregon State University; Hollenbeck, Vicky; Martin, Ruth

Submitted to: Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/19/2020
Publication Date: 6/21/2020
Citation: Dombrowski, J.E., Kronmiller, B.A., Hollenbeck, V.G., Martin, R.C. 2020. Transcriptome analysis of wounding in the model grass Lolium temulentum. Plants. 9(6):780. https://doi.org/10.3390/plants9060780.
DOI: https://doi.org/10.3390/plants9060780

Interpretive Summary: Grasses are subjected to a variety of stresses on any given day. For forage and turf grasses, wound stress is one of the most predominate stresses that they are exposed to on a continual basis. Damage or loss of plant tissue occurs when plants are crushed by treading, grazing, feeding insects, or cutting by mowing or hay production. Most of these wound stresses result in extensive loss of vegetative tissues and rapid regrowth. Very little is known concerning the molecular responses to wound stress in these valuable and extensively used plants. Sequencing of gene expression libraries generated from grass plants exposed to severe wounding identified 9413 up- and 7704 down-regulated distinct 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. 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: Wounding is the most predominant stress forage and turf grasses are exposed to on a continual basis. Damage or loss of plant tissue occurs when plants are crushed by treading, grazing, feeding insects, or cutting by mowing or harvesting hay. Most of these wound stresses result in extensive loss of vegetative tissues followed by rapid regrowth. This type of damage and response is predominantly associated with forage and turf grass species. RNA-Seq generated transcriptome of Lolium plants subjected to severe wounding revealed 9413 up- and 7704 down-regulated distinct differentially-expressed sequences (DES). Gene Ontology analysis revealed a strong emphasis on cell and metabolic processes, and categories associated with binding and organelles. Signaling, transporter activity and photosynthesis related categories were enriched for up-regulated DES, and protein folding and reproduction categories were enriched in down-regulated DES. Kinases comprised over 6.8% of the total DES found in the up-regulated DES dataset, of which 44% were receptor kinases. Chloroplast, transport, and transferase related DES each represented between 6.5 and 7% of the total up-regulated DES. Specifically, sequences annotated for enzymes involved in the biosynthesis of jasmonic acid and other plant hormones, mitogen-activated protein kinases, WRKY transcription factors, proteinase inhibitors, cell wall modifying enzymes and brassinosteroid receptors were identified. Furthermore, a variety of pathogen defense related DES were also found to be induced by wounding. Surprisingly heat shock and chaperone DES were three times more prevalent in the down-regulated DES when compared to the up-regulated DES. The analysis of this wound transcriptome is the first step at identifying the molecular components and pathways used by grasses to respond to wounding. The information gained from the analysis will 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.