I'm not sure where you get he 150-300,000 number, but when I go to the NCBI at look at their entries for the wheat genome, it seems to have about 27,000 protein

I'm not sure where you get he 150-300,000 number, but when I go to the NCBI at look at their entries for the wheat genome, it seems to have about 27,000 proteins, just like most other plants. Regardless of DNA content, most higher organisms seem to have between 10-30,000 protein coding genes.