title: Biological implications of the occurrence of 32 members of the XTH (xyloglucan endotransglucosylase/hydrolase) family of proteins in the bryophyte Physcomitrella patens.
abstract: This comprehensive overview of the xyloglucan endotransglucosylase/hydrolase (XTH) family of genes and proteins in bryophytes, based on research using genomic resources that are newly available for the moss Physcomitrella patens, provides new insights into plant evolution. In angiosperms, the XTH genes are found in large multi-gene families, probably reflecting the diverse roles of individual XTHs in various cell types. As there are fewer cell types in P. patens than in angiosperms such as Arabidopsis and rice, it is tempting to deduce that there are fewer XTH family genes in bryophytes. However, the present study unexpectedly identified as many as 32 genes that potentially encode XTH family proteins in the genome of P. patens, constituting a fairly large multi-gene family that is comparable in size with those of Arabidopsis and rice. In situ localization of xyloglucan endotransglucosylase activity in this moss indicates that some P. patens XTH proteins exhibit biochemical functions similar to those found in angiosperms, and that their expression profiles are tissue-dependent. However, comparison of structural features of families of XTH genes between P. patens and angiosperms demonstrated the existence of several bryophyte-specific XTH genes with distinct structural and functional features that are not found in angiosperms. These bryophyte-specific XTH genes might have evolved to meet morphological and functional needs specific to the bryophyte. These findings raise interesting questions about the biological implications of the XTH family of proteins in non-seed plants.
authors.affiliation: Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences, Tohoku University, Sendai 980-8578, Japan.
authors.forename: Ryusuke
authors.initials: R
authors.lastname: Yokoyama
authors.forename: Yohei
authors.initials: Y
authors.lastname: Uwagaki
authors.forename: Hiroki
authors.initials: H
authors.lastname: Sasaki
authors.forename: Taro
authors.initials: T
authors.lastname: Harada
authors.forename: Yuji
authors.initials: Y
authors.lastname: Hiwatashi
authors.forename: Mitsuyasu
authors.initials: M
authors.lastname: Hasebe
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Nishitani
mesh_terms: D000595:Amino Acid Sequence; D019068:Bryopsida / Q000201:enzymology / Q000235:genetics*; D019143:Evolution, Molecular; D020869:Gene Expression Profiling; D017343:Genes, Plant; D016695:Glycosyltransferases / Q000235:genetics* / Q000378:metabolism; D007150:Immunohistochemistry; D008969:Molecular Sequence Data; D005810:Multigene Family; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D010940:Plant Proteins; D016695:Glycosyltransferases; C473049:xyloglucan - xyloglucosyltransferase