Auxin-Induced Changes in the Cell Wall Xyloglucans: Effects of Auxin on the Two Different Subtractions of Xyloglucans in the Epicotyl Cell Wall of <italic>Vigna angularis</italic><xref ref-type="fn" rid="fn1"><sup>1</sup></xref>

Abstract

In order to study the IAA-induced modifications of the cell wall of azuki bean (Vigna angularis Ohwi et Ohashi cv. Takara) epicotyl segments, the xyloglucans were subfractionated into two components, i.e., 4K-U and 24K xyloglucans, which were obtained by extraction with 4% KOH solution containing 8 M urea and 24% KOH solution, respectively. The weight-average molecular weights of 4K-U and 24K xyloglucans were estimated to be 40 × 104 and 106 × 104, respectively. Complete acid hydrolysis of 4K-U and 24K xyloglucans gave glucose, xylose, galactose and fucose in mole % 48.3 : 33.5 : 13.8 : 4.4 and 45.3 : 30.9 : 19.6 : 4.3, respectively. Treatment of epicotyl segments with IAA (0.1 mM) caused a decrease in the amount of 24K xyloglucans and an increase in 4K-U xyloglucans, whereas the total amount of the two xyloglucans remained constant. Furthermore, IAA treatment caused a decrease in the molecular weight of 24K xyloglucans from 106 × 104 to 78 × 104 without causing changes in their sugar compositions. With 4K-U xyloglucans, IAA caused an increase in the mole % of xylose and a decrease in the mole % of galactose and fucose.