A splicing regulator, SR45, suppresses plant immunity via regulating salicylic acid pathway in arabidopsis thaliana

Authors: BUI, AUDREY - St Bonaventure University; BUI, ARDEN - St Bonaventure University; GUJRAL, IESH - St Bonaventure University; FAN, SERENA - St Bonaventure University; LONG, ANTHONY - Bronx High School Of Science; HU, ANNA - St Bonaventure University; CHIN, CHRISTOPHER - St Bonaventure University; POWERS, JORDAN - St Bonaventure University; Yang, Ronghui; GAO, MIN - University Of Maryland; ZHANG, CHING - University Of Maryland; LU, HUA - University Of Maryland; Cooper, Bret; ZHANG, XIAO-NING - St Bonaventure University

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/19/2025
Publication Date: 10/31/2025
Citation: Bui, A., Bui, A., Gujral, I., Fan, S., Long, A., Hu, A., Chin, C., Powers, J., Yang, R., Gao, M., Zhang, C., Lu, H., Cooper, B., Zhang, X. 2025. A splicing regulator, SR45, suppresses plant immunity via regulating salicylic acid pathway in arabidopsis thaliana. Frontiers in Plant Science. 16. Article e1704701. https://doi.org/10.3389/fpls.2025.1704701.
DOI: https://doi.org/10.3389/fpls.2025.1704701

Interpretive Summary: In plant cells, RNA message is made from DNA, the heritable genetic material. In turn, proteins, which have structural and enzymatic functions, are made from messenger RNA. In a cellular process called splicing, small parts of messenger RNA are cut away from larger RNA molecules such that the smaller RNA encodes a protein that is different (smaller) than the protein from the larger RNA. It has been demonstrated in plants that splicing helps make different proteins that then have different functions. How splicing affects disease resistance in plants is not fully resolved. It is known that a protein called SR45 is important for splicing in the model plant Arabidopsis. SR45 has two splice forms, SR45.1 and SR45.2. Research in this report revealed that mutants missing SR45.1 had increased amounts of pipecolic acid, a hormone that regulates disease resistance, had increased resistance to pathogens, and produced alternate spliced RNA for genes involved in disease resistance. In summary, SR45.1 regulates through splicing a set of genes involved in disease resistance. These data are most likely to influence scientists at universities, government agencies and companies who are studying disease resistance in important crops like corn, beans, tomatoes, and soybeans.

Technical Abstract: Facing constant challenges from various pathogens and pests, plants have evolved different strategies to defend themselves both locally and systemically. A global change in RNA metabolism is one of the necessary steps to mount on a long-lasting immunity against present and future invasions. Arabidopsis Serine/Arginine-rich 45(SR45) is an evolutionarily conserved RNA binding protein that regulates multiple steps of RNA metabolism. Out prior study suggests that SR45 acts as a negative regulator of plant immunity. To better understand the molecular mechanism for SR45’s defense role, we examined the metabolic profile in both Col-0 and sr45-1. The results showed a significant accumulation of pipecolic acid (Pip), salicylic acid (SA) and other potential defense compounds in sr45-1, indicating an increased systemic immunity. The sr45-1 mutant exhibited an elevated resistance to a wide-range of biotrophic pathogen species and its insensitivity to Pip, SA and pathogen-pretreatment. Between the two alternatively spliced isoforms, SR45.1 and SR45.2, SR45.1 seemed to be the culprit for the observed immune suppression. Upon examinations of the transcriptome profile between Col-0 and sr45-1 either under mock or P. syringae PmaDG3 challenge, 1125 genes were identified as SR45-suppressed and PmaDG3-induced. Genes function in SA biosynthesis and systemic acquired resistance was overrepresented, including the ones coding for WRKY, RLK, RLP, protein kinases and TIR-NBSLRR proteins. In addition, significant alternative splicing activity were identified in a list of genes either due to sr45-1 alone or both sr45-1 and PmaDG3 challenge. Among them, we characterized the effect of alternative splicing in two candidates, CBRLK1 and SRF1. Interestingly, alternative splicing in both of them exhibited a switch between receptor-like protein (RLP) and receptor-like kinase (RLK) in the predicted protein products. Overexpressing their sr45-1 dominant isoform in Col-0 led to a partial increase in immunity, suggesting the involvement of both alternative splicing events in SR45-conferred immune suppression. In summary, we hypothesize that SR45 regulates a subset of immune genes at either transcriptional or co-transcriptional pre-mRNA splicing levels to confer its function in a systemic immune suppression.