That's complete bollocks. Pagerank is only affected by the quality and quantity of backlinks you have.
Niche, keywords, color of your template or anything else has absoltely no effect on Pagerank.
The only other parameter that could effect your pagerank is domain age due to it having latent backlinks from older sources.
Keep in mind however that Pagerank has absolutely nothing to do with how well you website will perform in the search engine. It doesn't matter for diddly squat.
I have a PR1 website that gets 1,500 organic users a day while one of my PR5 websites gets only 10.