title: Alpha-expansins in the semiaquatic ferns Marsilea quadrifolia and Regnellidium diphyllum: evolutionary aspects and physiological role in rachis elongation.
abstract: To investigate the evolutionary history of expansins and their role in cell elongation in early land plants, we isolated two alpha-expansin genes, Mq-EXP1 and Rd-EXP1, respectively, from the semiaquatic ferns Marsilea quacdrifolia L. and Regnellidium diphyllum Lindm. The deduced amino acid sequences of the fern expansins exhibit a high degree of identity to those of seed plants, showing that expansin genes were conserved during the evolution of vascular plants. Gel-blot analysis of M. quadrifolia and R. diphyllum genomic DNA indicated that, in both ferns, alpha-expansins are encoded by multigene families. Expression of alpha-expansin genes probed with Mq-EXP1 was confined to the elongating region of the Marsilea rachis. Cell-wall proteins of M. quadrifolia induced in-vitro extension of acidified cucumber cell walls. In R. diphyllum, expression of Rd-EXP1 increased when elongation of the rachis was enhanced by submergence or ethylene. These results indicate that alpha-expansins act as wall-loosening proteins in ferns, as has been proposed for angiosperms. In addition, Rd-EXP1 may play a role in mediating elongation of the rachis in submerged plants.
authors.affiliation: MSU-DOE Plant  Research Laboratory, Michigan State University, East Lansing 48824-1312, USA.
authors.forename: J H
authors.initials: JH
authors.lastname: Kim
authors.forename: H T
authors.initials: HT
authors.lastname: Cho
authors.forename: H
authors.initials: H
authors.lastname: Kende
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D005075:Biological Evolution; D018744:DNA, Plant; D005030:Ethylenes / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D018521:Plant Physiological Phenomena; D010940:Plant Proteins / Q000145:classification / Q000235:genetics*; D010944:Plants / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism; D018749:RNA, Plant / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D018744:DNA, Plant; D005030:Ethylenes; D010940:Plant Proteins; D012333:RNA, Messenger; D018749:RNA, Plant; C095825:expansin protein, plant; C036216:ethylene