Poster: Signaling, long distance

Abs # 453: Comprehensive analysis of Perilla and Arabidopsis phloem exudate to characterize compounds involved in floral induction

Presenter:	Hoffmann-Benning, Susanne , hoffma16@msu.edu
Authors	Lydic, Todd  (B)   Shimojima, Mie  (B)   Zeevaart, Jan AD (A)   Hoffmann-Benning, Susanne  (B)
Affiliations:	(A): Michigan State University-DOE-Plant Research Laboratory (B): Michigan State University- Dept. of Biochemistry and Molecular Biology

The phloem is known to transport sugars, peptides/proteins, RNA, and other plant metabolites, many of which play an important role in signalling and/or plant growth and development. One of the signals known to be transported in the phloem is florigen. However, its identity remains one of the major mysteries in plant science. We have compared peptides and protein in the phloem exudates of flowering and non-flowering Perilla plants and identified several peptides/small proteins that appear to be induced upon the induction of flowering, including proteins with similarity to purine permease, AP2, hydroxyproline-rich glycoproteins, and protein kinases (Hoffmann-Benning et al., 2002). We created a Perilla leaf cDNA library and cloned the genes encoding several of the proteins of interest. Northern analysis will show whether these are indeed induced in flowering plants. One of the problems in identifying proteins in Perilla phloem sap is that only few sequences are available in public databases. For this reason, we started a comprehensive analysis of Arabidopsis phloem sap. So far, we have been able to identify 11 proteins. Since the chemical identity of florigen remains unknown, we started to characterize metabolites present in both Perilla and Arabidopsis phloem exudates. We are also growing and analyzing SALK knock-out plants for genes with homology to those first identified in Perilla. This work was supported by the MSU Research of Excellence Fund, Plant Products and Technologies to SHB.