During the past years it has been shown that RNA (ribonucleic acid) molecules, in addition to their roles as a molecular template for protein production, also play important roles in cell-to-cell and long distance signaling implants. RNAs have been implicated in the coordination of important physiological responses like nutrient partitioning, virus and pathogen defense and gene silencing. They are transmitted via the plant phloem (plant tissue that carries organic nutrients especially the sugar sucrose). A new review paper published by the Journal of Experimental Botany summarizes the current knowledge on the roles of phloem RNAs. RNAs that are transmitted in the phloem is known to be of three types.

• Small non-coding RNA, which are important in control of gene expression. They are classified in two types, short interfering (siRNA) and micro (miRNA) RNA
• RNA genomes of viruses transmitted during infection
• Cellular mRNA expressed in distant tissues

In depth understanding of long distance RNA transport can lead to the development of crops that are resistant to abiotic stresses or viral diseases.

The review is available to subscribers at http://jxb.oxfordjournals.org/cgi/content/full/59/1/85 Non subscribers can read the abstract at http://jxb.oxfordjournals.org/cgi/content/abstract/59/1/85http://jxb.oxfordjournals.org/cgi/content/full/59/1/85