Xyloglucan endotransglycosylases have a function during the formation of secondary cell walls of vascular tissues.
Xyloglucan transglycosylases (XETs) have been implicated in many aspects of cell wall biosynthesis, but their function in vascular tissues, in general, and in the formation of secondary walls, in particular, is less well understood. Using an in situ XET activity assay in poplar stems, we have demonstrated XET activity in xylem and phloem fibers at the stage of secondary wall formation. Immunolocalization of fucosylated xylogucan with CCRC-M1 antibodies showed that levels of this species increased at the border between the primary and secondary wall layers at the time of secondary wall deposition. Furthermore, one of the most abundant XET isoforms in secondary vascular tissues (PttXET16A) was cloned and immunolocalized to fibers at the stage of secondary wall formation. Together, these data strongly suggest that XET has a previously unreported role in restructuring primary walls at the time when secondary wall layers are deposited, probably creating and reinforcing the connections between the primary and secondary wall layers. We also observed that xylogucan is incorporated at a high level in the inner layer of nacreous walls of mature sieve tube elements.
Bourquin
Veronica
V
Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden.
Nishikubo
Nobuyuki
N
Abe
Hisashi
H
Brumer
Harry
H
Denman
Stuart
S
Eklund
Marlin
M
Christiernin
Maria
M
Teeri
Tunla T
TT
Sundberg
Björn
B
Mellerowicz
Ewa J
EJ
D000595:Amino Acid Sequence; D002454:Cell Differentiation / Q000235:genetics / Q000502:physiology; D002473:Cell Wall / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D003001:Cloning, Molecular; D016695:Glycosyltransferases / Q000235:genetics* / Q000378:metabolism*; D007150:Immunohistochemistry; D016253:Microscopy, Immunoelectron; D008969:Molecular Sequence Data; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D018514:Plant Structures / Q000201:enzymology / Q000235:genetics / Q000254:growth & development* / Q000648:ultrastructure; D032107:Populus / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development
D010940:Plant Proteins; D016695:Glycosyltransferases; C073693:xyloglucan endotransglycosylase