title: Water deficit modulates gene expression in growing zones of soybean seedlings. Analysis of differentially expressed cDNAs, a new beta-tubulin gene, and expression of genes encoding cell wall proteins.
abstract: Transfer of soybean seedlings to low-water-potential vermiculite (psi w = -0.3 MPa) results in a reversible decrease in hypocotyl growth and modulation of several polysomal mRNAs (Plant Physiol 92: 205-214). We report here the isolation of two cDNA clones (pGE16 and pGE95) which correspond to genes whose mRNA levels are increased, and one cDNA clone (pGE23) which corresponds to a gene whose mRNA level is decreased in the hypocotyl zone of cell elongation by water deficit. In well-watered seedlings mRNAs hybridizing to pGE16 and pGE95 are most abundant in mature regions of the seedling, but in water-deficient seedlings mRNA levels are reduced in mature regions and enhanced in elongating regions. RNA corresponding to soybean proline-rich protein 1 (sbPRP1) shows a similar tissue distribution and response to water deficit. In contrast, in well-watered seedlings, the gene corresponding to pGE23 was highly expressed in the hypocotyl and root growing zones. Transfer of seedlings to low-water-potential vermiculite caused a rapid decrease in mRNA hybridizing to pGE23. Sequence analysis revealed that pGE23 has high homology with beta-tubulin. Water deficit also reduced the level of mRNA hybridizing to JCW1, an auxin-modulated gene, although with different kinetics. Furthermore, mRNA encoding actin, glycine-rich proteins (GRPs), and hydroxyproline-rich glycoproteins (HRGPs) were down-regulated in the hypocotyl zone of elongation of seedlings exposed to water deficit. No effect of water deficit was observed on the expression of chalcone synthase. Decreased expression of beta-tubulin, actin, JCW1, HRGP and GRP and increased expression of sbPRP1, pGE95 and pGE16 in the hypocotyl zone of cell elongation could participate in the reversible growth inhibition observed in water-deficient soybean seedlings.
authors.affiliation: Department of Biochemistry and Biophysics, Texas A&M University, College Station 77843.
authors.forename: R A
authors.initials: RA
authors.lastname: Creelman
authors.forename: J E
authors.initials: JE
authors.lastname: Mullet
mesh_terms: D000199:Actins / Q000235:genetics; D000217:Acyltransferases / Q000235:genetics; D000595:Amino Acid Sequence; D001483:Base Sequence; D015152:Blotting, Northern; D002473:Cell Wall / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005786:Gene Expression Regulation / Q000187:drug effects*; D007700:Kinetics; D008969:Molecular Sequence Data; D010455:Peptides / Q000235:genetics; D010937:Plant Growth Regulators / Q000494:pharmacology; D010940:Plant Proteins / Q000235:genetics*; D016133:Polymerase Chain Reaction; D055232:Proline-Rich Protein Domains; D013025:Glycine max / Q000187:drug effects / Q000235:genetics / Q000254:growth & development*; D014404:Tubulin / Q000235:genetics*; D014867:Water / Q000378:metabolism*
chemical_list: D000199:Actins; C058257:GRP protein, Phaseolus vulgaris; D010455:Peptides; D010937:Plant Growth Regulators; D010940:Plant Proteins; D014404:Tubulin; D014867:Water; D000217:Acyltransferases; C020141:flavanone synthetase