NATHAN R. Johnson
Penn State University
Cuscuta is a genus of vine-like parasitic plants which constrict and invade the stems of host plants, forming a symplastic interface through a specialized organ called a haustorium. We recently showed that Cuscuta campestris exerts influence on the host through this connection, producing a cohort of miRNAs that down-regulate numerous target Arabidopsis thaliana genes. The discovery of this exciting form of parasitic effector led us to investigate if these miRNAs are produced by a second species of Cuscuta, C. gronovii. We performed sRNA sequencing on C. gronovii attachments to A. thaliana, sampling both the parasite-host haustorial interface and adjacent tissues in both plants. Analysis revealed over 200 C. gronovii small RNAs which are up-regulated in the interface, most being sizes common to miRNAs (21 or 22 nucleotides in length). Surprisingly, none of these haustorially-induced C. gronovii small RNAs were identical in sequence to our previously identified set of C. campestris haustorially-induced microRNAs. We identified several A. thaliana mRNAs that were targeted by induced C. gronovii small RNAs based on complementarity and induced secondary siRNA accumulation during parasitism. Verified targets of induced C. gronovii small RNAs include MPK3, which encodes a kinase implicated in plant defense responses, and MYB103, which encodes a transcription factor involved in cell-wall biosynthesis. Interestingly, one confirmed A. thaliana mRNA target was shared between C. campestris and C. gronovii: SEOR1, which encodes a P-protein which affects leakage of sugars after wounding. However, the SEOR1-targeting small RNAs from C. campestris differ substantially from those of C. gronovii in sequence. We conclude that trans-species active small RNAs are present and functional in both of the Cuscuta species we’ve examined to date, but that their sequences have diverged substantially. This raises the hypothesis that trans-species active small RNAs may be a common but quickly evolving feature within the Cuscuta genus.
Penn State University
The asset you are trying to access is locked. Please enter your access key to unlock.