Dear Robin and other yeast-netters,
the hypothesis about the importance of cell wall hardness is interesting
but there are two reasons why I am not inclined to believe it (in the
absence of hard data, it's just a guess):
1. Pombe is much more difficult to spheroplast than cerevisiae. The
cell wall of fission yeast is surely made from a different material
than that of budding yeast. I would expect that it may be harder,
since it is so difficult to find enzymes that would eat it (the snail
enzyme mix known as glusulase just makes little holes on the growing
end of S. pombe cells).
2. And what about plants? They are pretty hard, too.