Proteomic and transcriptomic analyses using the
growing resources of genomic information have been applied
to identification of macromolecules in exudates collected from
phloem. Most of the analyses rely on collection of exudate
following incisions made to the vasculature, but some limited
data are available for exudates collected from excised aphid
stylets. Species examined, to date, include a number of cereals
(rice, barley, and wheat), a number of cucurbits, castor bean,
members of the genus Lupinus, brassicas, and Arabidopsis.
As many as 1,100 proteins, some hundreds of transcripts, and
a growing number of small ribonucleic acids (RNAs),
including micro-RNAs, have been identified across the
species with a high degree of commonality. Questions
relating to the nature and extent of contamination of sieve
element contents with those of surrounding companion cells
and nonvascular cells are addressed together with likely
functions of identified macromolecules. The review considers
likely translocation and systemic signaling functions among
the macromolecular inventory of phloem exudates
