Talk abstracts

Talk on Saturday 09:15-09:30am submitted by Lichun Zhou

Cleavage and Polyadenylation Specificity Factor (CPSF30) involved in plant immunity system

Lichun Zhou (Department of Plant and Soil Sciences, University of Kentucky, Lexington KY 40546, USA), Huazhen Liu (Department of Plant Pathology, University of Kentucky, Lexington, KY 40546, USA), Pradeep Kachroo (Department of Plant Pathology, University of Kentucky, Lexington, KY 40546, USA), Arthur G. Hunt (Department of Plant and Soil Sciences, University of Kentucky, Lexington KY 40546, USA)

In plants, Systemic Acquired Resistance (SAR) is a form of systemic immunity that protects uninfected parts of a pathogen-inoculated plant against further disease. In a previous study, it was shown that a novel plant polyadenylation factor subunit, CPSF30, is required for resistance against a bacterial pathogen [1]. The Arabidopsis thaliana ortholog of the 30-kD subunit of the mammalian Cleavage and Polyadenylation Specificity Factor(CPSF30) gene encodes two proteins, CPSF30S and CPSF30L. To better understand how CPSF30 contributes to resistance to plant pathogens, we treated a set of mutant and complemented Arabidopsis lines with an avirulent strain of Pseudomonas syringae to induce SAR. The set of lines included a mutant (oxt6) that does not express CPSF30 as well as lines that express either CPSF30S, CPSF30L, or both proteins in the oxt6 background. The results show that lines that express CPSF30S can establish an SAR, but lines that do not express CPSF30S are deficient in SAR. All of the wild type, mutant, and transgenic plants have similar transcriptional responses in the inoculated leaf to the avirulent pathogen. However, they differ in the (immune) distal leaves, and the differences relate to the well-established transcriptional response in SAR. We conclude that CPSF30S is acting downstream from the initial challenge by the avirulent pathogen and outside of the inoculated leaf. In a recent study, it has shown that the non-coding RNA TAS3a is a precursor for tasi-RNAs D7 and D8, which are early mobile signals for SAR [2]. TAS3a transcripts undergo alternative polyadenylation, and poly(A) site choice affects the ability to generate the D7 and D8 tasi-RNAs. We observed TAS3a poly(A) site usage shift from distal to proximal in plants that do not make CPSF30S. We propose that CPSF30S-dependent usage of the distal TAS3a poly(A) site is the mechanism that links CPSF30 with SAR. Taken together, these studies provide new insights into the connections between mRNA polyadenylation and the plant immune system.

1. Bruggeman, Q., et al., The Polyadenylation Factor Subunit CLEAVAGE AND POLYADENYLATION SPECIFICITY FACTOR30: A Key Factor of Programmed Cell Death and a Regulator of Immunity in Arabidopsis. Plant Physiol, 2014. 165(2): p. 732-746.
2. Shine et al., Phased small RNA–mediated systemic signaling in plants. Science Advance, 2022.

Keywords: Plant RNA polyadenylation, Systemic Acquired Resistance, tasi-RNAs