RT Journal Article SR Electronic T1 MicroRNAs from the parasitic plant Cuscuta campestris target host messenger RNAs JF bioRxiv FD Cold Spring Harbor Laboratory SP 180497 DO 10.1101/180497 A1 Saima Shahid A1 Gunjune Kim A1 Nathan R. Johnson A1 Eric Wafula A1 Feng Wang A1 Ceyda Coruh A1 Vivian Bernal-Galeano A1 Tamia Phifer A1 Claude W. dePamphilis A1 James H. Westwood A1 Michael J. Axtell YR 2017 UL http://biorxiv.org/content/early/2017/09/29/180497.abstract AB Dodders (Cuscuta spp.) are obligate parasitic plants that obtain water and nutrients from the stems of host plants via specialized feeding structures called haustoria. Dodder haustoria facilitate bi-directional movement of viruses, proteins, and mRNAs between host and parasite1, but the functional effects of these movements are not clear. Here we show that C. campestris haustoria accumulate high levels of many novel microRNAs (miRNAs) while parasitizing Arabidopsis thaliana hosts. Many of these miRNAs are 22 nts long, a usually rare size of plant miRNA associated with amplification of target silencing through secondary small interfering RNA (siRNA) production2. Several A. thaliana mRNAs are targeted by C. campestris 22 nt miRNAs during parasitism, resulting in mRNA cleavage, secondary siRNA production, and decreased mRNA accumulation levels. Hosts with mutations in two of the targets supported significantly higher growth of C. campestris. Homologs of target mRNAs from diverse plants also have predicted target sites to induced C. campestris miRNAs, and the same miRNAs are expressed and active against host targets when C. campestris parasitizes a different host, Nicotiana benthamiana. These data show that C. campestris miRNAs act as trans-species regulators of host gene expression, and suggest that they may act as virulence factors during parasitism.