Poster: Seed Biology

Abs # 541: Characterization and expression of polyphenol oxidase in developing grain of wheat (Triticum aestivum L).

Presenter:	Anderson, James V, andersjv@fargo.ars.usda.gov
Authors	Anderson, James V (A)   Morris, Craig F (B)
Affiliations:	(A): USDA-ARS, BRL, Fargo, ND 58105-5674 (B): USDA-ARS, WWQL, WSU, Pullman, WA 99164-6394

Polyphenol oxidase (PPO) is implicated as the primary causative agent resulting in inferior color quality in Asian noodle and steamed bread production. To further study the properties of PPO on end-quality characteristics at the molecular level, degenerate oligonucleotides were designed based on conserved PPO sequences and/or amino acid sequences obtained from tryptic-digested fragments of purified wheat grain PPO (Anderson and Morris, Cereal Chem., 80(2), 2003). Using this approach, we have successfully PCR-amplified and cloned three partial genomic wheat PPOs. Two of the partial wheat genomic clones (TaPPO1 and TaPPO2) are 97.5% similar (over 1040 base pair) at the nucleotide level, contain two introns, and have different endonuclease restriction sites within the exon-coding region. BLASTX analysis showed that TaPPO1 and TaPPO2 have the greatest sequence identity to previously identified pineapple (Ananas comosus) PPO. BLASTX analysis resulting from our third partial genomic wheat PPO (TaPPO3) showed 96% similarity to a previously reported wheat PPO (accession# AF507945). Wheat TaPPO3 differs from TaPPO1 and TaPPO2 by having no identified introns and showing less than 50% sequence identity over common coding regions. RNA blots hybridized with TaPPO1 or TaPPO2 showed maximum PPO expression in developing wheat grain (cultivar Penawawa) between 14 and 21 days post-anthesis (dpa) whereas, RNA blots probed with TaPPO3 showed no hybridization in developing wheat grain between 0 to 35 dpa. Further characterization of the two distinctly different wheat PPOs and expression profiles from four cultivars of wheat grain with varying end-quality color characteristics will be presented.