Journal Article

Endoxyloglucan Transferase cDNA Isolated from Pea Roots and Its Fluctuating Expression in Hydrotropically Responding Roots

Mamoru Takano, Nobuharu Fujii, Atsushi Higashitani, Kazuhiko Nishitani, Tadashi Hirasawa and Hideyuki Takahashi

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 40, issue 2, pages 135-142
Published in print January 1999 | ISSN: 0032-0781
Published online January 1999 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/oxfordjournals.pcp.a029520
Endoxyloglucan Transferase cDNA Isolated from Pea Roots and Its Fluctuating Expression in Hydrotropically Responding Roots

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We isolated an endoxyloglucan transferase cDNA (Ps-EXGT1) from the roots of an agravitropic pea mutant, ageotropum. The putative product of the cDNA was 34.1 kDa and consisted of 293 amino acid residues. The predicted amino acid sequence was 75.1–88.6% identical to those of EXGT genes in other plants. The Ps-EXGT1 cDNA was strongly expressed in elongating roots and stems but not in either mature stems or young leaves. In roots, the transcription level of Ps-EXGT1 was most abundant in the rapidly growing region. When root elongation was inhibited by a water stress, Ps-EXGT1 transcription was repressed. The roots curved hydrotropically due to differential growth of the cortical cells in the elongation zone when the root cap was exposed to a gradient of water potential; the length of the cells on the side of lower water potential was much longer than those on the side of higher water potential. The expression pattern of Ps EXGT1 in the hydrotropically responding roots fluctuated between the side of the higher water potential and that of the lower water potential in the elongation zone. In other words, the accumulation of Ps-EXGT1 mRNA was much greater on the side of lower water potential than on that of higher potential just prior to the commencement of positive hydrotropism. When the roots started to curve slightly away from the side of higher water potential causing a rhythmic oscillatory movement [Take et al. (1995) Planta 197: 4101, there was more transcription of Ps EXGT1 on the side of higher water potential. These results suggest that the transcription of Ps-EXGT1 is involved in cell growth and that this regulation of transcription plays a role in the differential growth of hydrotropically responding roots.

Keywords: Ageotropum; Cell extension; EXGT (EC 2.4.1.-); Hydrotropism; Pisum sativum L.; Root

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Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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