Poster: Late and Moved Abstracts

Abs # 1431: Identification and characterization of TvPirin as a candidate gene for haustorium development in the parasitic plant Triphysaria

Presenter:	Ngo, Quy A, qango@ucdavis.edu
Authors	Ngo, Quy A (A) (B)  Yoder, John I (A) (C)
Affiliations:	(A): University of California - Davis (B): Genetics Graduate Group (C): Vegetable Crops Department

The parasitic plants Triphysaria use their haustoria at the subapical root tip regions to invade and withdraw water and nutrients from host plant roots via the xylem connection. The two most active haustorium inducers, 2,6-dimethoxybenzoquinone (DMBQ) and peonidin (Pn), differ in their phytotoxicity on Triphysaria roots. DMBQ causes root necrosis and decreases haustorium formation frequency at 50mM and above whereas Pn does not exhibit these effects at concentrations up to 1mM. We have identified the TvPirin gene upregulated by both these inducers but not by the non-inducer juglone, a quinone similar to DMBQ in its phytotoxicity. This upregulation pattern is strongest in the root region of the haustorium phenotype, less so in the remaining of the roots, and not detected in the shoots of Triphysaria. Using 5'- and 3'-RACE, we have cloned the TvPirin full-length cDNA containing an ORF of a 288aa protein and the genomic TvPirin with 6 introns organized differently from the introns of all four Arabidopsis Pirin homologs. TvPirin has homologs in other plant species, humans, rodents, and a variety of bacteria. The His(6x)-TvPirin protein overexpressed in E. coli on SDS-PAGE gels migrates to the predicted size of ~36kD. We are currently investigating TvPirin protein levels and its transcript tissue-specific localization in Triphysaria roots in the presence and absence of haustorium inducers. We are also testing TvPirin's involvement in haustorium development by gene silencing with RNAi and ectopic expression under a chemical inducible promoter in transgenic Triphysaria plants.