Variation in two PPO genes associated with polyphenol oxidase activity in seeds of common wheat
Polyphenol oxidase (PPO) is often regarded as a major factor resulting in time dependent darkening and discoloration of Asian noodles and other wheat end products. To understand the relationship between variation of PPO genes and PPO activity of seed, the three PPO genes, which express in immature wheat grain, were investigated in 216 common wheat cultivars. The results indicated that only TaPPO A1 and TaPPO D1 showed high polymorphisms related to PPO activity. Two alleles in both TaPPO A1 (TaPPO A1a and TaPPO A1b) and TaPPO D1 (TaPPO D1a and TaPPO D1b) were detected using denaturing polyacrylamide gel electrophoresis. Wheat cultivars with TaPPO A1b usually showed higher PPO activity than those with TaPPO A1a. The TaPPO D1a allele was often found in lower PPO activity cultivars, compared with TaPPO D1b. The sequencing results of DNA fragments confirmed that two introns existed in TaPPO D1 like TaPPO A1. Some variation of introns was detected in the two alleles of TaPPO D1. During seed development, the high PPO activity cultivar, Yangmai 158 (TaPPO A1b/TaPPO D1b) showed higher transcription of the two PPO genes, in comparison to low activity cultivar, Yongchuanbaimai (TaPPO A1a/TaPPO D1a) These results suggested that variation in introns may influence the transcription of TaPPO A1 and TaPPO D1 in immature seeds of wheat.
Euphytica