A method of processing plant cellulose includes providing plant cellulose that is from a plant expressing a CESA polypeptide variant having at least one amino acid mutation in its carboxy-terminal transmembrane region; and saccharifying the plant cellulose to produce fermentable sugars. The method can also include fermenting the fermentable sugars to produce alcohol. A method of producing a plant having beneficial saccharification properties includes introducing into a plant a polynucleotide encoding a CESA polypeptide variant having at least one amino acid mutation in its carboxy-terminal transmembrane region; and expressing in the plant the CESA polypeptide variant, wherein plant cellulose of the plant expressing the CESA polypeptide variant has beneficial saccharification properties as compared to a wild-type plant.