Investigating interface-induced microRNA accumulation and regulation of the parasitic plant Cuscuta campestris
Open Access
- Author:
- Hudzik, Collin
- Graduate Program:
- Plant Biology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- June 05, 2023
- Committee Members:
- Cristina Rosa, Outside Unit & Field Member
Michael Axtell, Chair & Dissertation Advisor
Claude Depamphilis, Major Field Member
Gabriele Monshausen, Major Field Member
Teh-Hui Kao, Program Head/Chair - Keywords:
- microRNA
Cuscuta
Parasitic plants - Abstract:
- Small regulatory RNAs can move between organisms and regulate gene expression in the recipient. Several studies over the last decade have also shown that some small RNAs are exchanged between plants and their pathogens and parasites. The natural ability of plants to exchange small RNAs with invading eukaryotic organisms can be exploited to provide disease resistance. Conversely, pathogens can export small RNAs into their hosts in an attempt to increase their virulence. Whether the trans-species small RNAs being exported are distinguished from the normal endogenous small RNAs of the source organism is not known. The parasitic plant Cuscuta campestris (dodder) is a holoparasitic stem parasite which cannot sustain its own life without invading and growing on a host plant. Every year, Cuscuta campestris is responsible for damage to agriculturally important crops, often by reducing yield and acting as a vector for viruses to move from infected plants to healthy ones. Previous research has found that Cuscuta campestris produces many microRNAs that specifically accumulate at the host-parasite interface, several of which have been demonstrated to have trans-species activity. We have termed these as interface-induced microRNAs. Induction of C. campestris interface-induced microRNAs is similar regardless of host species and occurs in C. campestris haustoria produced in the absence of any host. It is likely that accumulation of interface-induced microRNAs is an inherent part of haustorium organogenesis. The loci-encoding C. campestris interface-induced microRNAs are distinguished by a common cis-regulatory element. This element is identical to a conserved upstream sequence element (USE) used by plant small nuclear RNA loci. The properties of the interface-induced microRNA primary transcripts strongly suggest that they are produced via U6-like transcription by RNA polymerase III. The USE promotes accumulation of interface-induced microRNAs (IIMs) in a heterologous system. This promoter element distinguishes C. campestris interface-induced microRNA loci from other plant small RNAs. These data suggests that C. campestris interface-induced microRNAs are produced in a manner distinct from canonical microRNAs. All confirmed C. campestris microRNAs with documented trans-species activity are interface-induced and possess these features. It is speculated that RNA polymerase III transcription of the interface-induced microRNAs may allow them to be exported to their hosts, while completely avoiding loading into the RNA induced silencing complexes in parasite tissues.