RNA trafficking in parasitic plant systems

Abstract

RNA trafficking in plants contributes to local and long-distance coordination of plant development and response to the environment. However, investigations of mobile RNA identity and function are hindered by the inherent difficulty of tracing a given molecule of RNA from its cell of origin to its destination. Several methods have been used to address this problem, but all are limited to some extent by constraints associated with accurately sampling phloem sap or detecting trafficked RNA. Certain parasitic plant species form symplastic connections to their hosts and thereby provide an additional system for studying RNA trafficking. The haustorial connections of Cuscuta and Phelipanche species are similar to graft junctions in that they are able to transmit mRNAs, viral RNAs, siRNAs, and proteins from the host plants to the parasite. In contrast to other graft systems, these parasites form connections with host species that span a wide phylogenetic range, such that a high degree of nucleotide sequence divergence may exist between host and parasites and allow confident identification of most host RNAs in the parasite system. The ability to identify host RNAs in parasites, and vice versa, will facilitate genomics approaches to understanding RNA trafficking. This review discusses the nature of host–parasite connections and the potential significance of host RNAs for the parasite. Additional research on host–parasite interactions is needed to interpret results of RNA trafficking studies, but parasitic plants may provide a fascinating new perspective on RNA trafficking.

Conversations between kingdoms: small RNAs

“…Bidirectional transfer of thousands of mRNAs between Cuscuta and two hosts, Arabidopsis and tomato, has been observed [68,69]. Host mRNA transcripts were tracked back in the dodder parenchyma at a distance of up to 30 cm away from the tomato/dodder connection [70].…”

Analysis of Metabolites in Stem Parasitic Plant Interactions: Interaction of Cuscuta–Momordica versus Cassytha–Ipomoea

“…Metabolite analyses are therefore the most realistic approach to understanding these interactions. Based on a report that macromolecules (e.g., mRNA and peptides) can translocate between Cuscuta and host plants [15], certain metabolites or macromolecules in the parasite could translocate into the host, triggering hypertrophy and subsequent vascular induction. …”

Quantification of tomato and Arabidopsis mobile RNAs trafficking into the parasitic plant Cuscuta pentagona

“…The parasite initiates haustoria at the points of contact with hosts and these specialized organs link the two plants in a physiological continuum that allows the translocation of water, nutrients and metabolites into the parasite. In addition to small molecules, a range of macromolecules, including RNAs and proteins, are mobile into C. pentagona (LeBlanc et al, 2012). However, apart from initial reports of RNA mobility, nothing is known about the specifics of the trafficking, function and fate of host RNAs in C. pentagona.…”