The cellulose synthase gene PrCESA10 is involved in cellulose biosynthesis in developing tracheids of the gymnosperm Pinus radiata

One full length (PrCESA10) and seven other cDNA clones (PrCESA2, 3, 5-8, 11) encoding cellulose synthases (CESAs) were isolated from the coniferous gymnosperm Pinus radiata. PrCESA10 encodes a protein predicted to contain the same domains and regions as angiosperm CESA genes: a zinc finger domain, a hypervariable region 1 (HVR1), a plant-conserved region (CR-P), a class-specific region or hypervariable region 2 (HVR2), in addition to the four conserved domains U1-U4 that are characteristic of the family 2 processive β-glycosyltransferases. The P. radiata protein is also predicted to contain eight transmembrane domains. The zinc finger domain, the CR-P and the C-terminal portion of the proteins, are highly conserved between P. radiata and the nearest angiosperm CESA protein from Solanum tuberosum. Reverse transcriptase-PCR showed that all the P. radiata genes were expressed in all organs tested, although to different extents. In situ hybridization studies with PrCESA10 in stems of 2- and 12-month-old seedlings showed that it was expressed in the secondary xylem in the two-to-three most recently developed tracheids, which were laying down secondary cell walls.