The auxin conjugate 1-O-indole-3-acetyl- -D-glucose is synthesized in immature legume seeds by IAGlc synthase and may be used for modification of some high molecular weight compounds

Abstract

Immature seeds of some dicotyledonous plants contain IAGlc synthase catalysing the synthesis of 1-O-IAGlc. This enzyme activity is comparable with 1-O-IAGlc synthase activity investigated earlier in liquid endosperm of Zea mays. Polyclonal antibodies against maize 1-O-IAGlc synthase cross-react with partially purified 1-O-IAGlc synthase from immature pea and rape seeds. Single immunoreactive bands were observed at a locus corresponding to 45.7 kDa and 43.7 kDa from pea and rape enzyme preparations, respectively, unlike that from the 50 kDa molecular mass of the maize enzyme. It was also observed that some high molecular weight compounds of pea seeds are labelled in vivo by [(14)C] IAA, and unlabelled 1-O-IAGlc inhibits that labelling. In immature pea seeds 43-49.8% of the IAA-modified high molecular weight compounds, obtained after ultracentrifugation, was found in the soluble fraction and 50.1-57% in the insoluble fraction. Ester-linked IAA accounted for about 6-9% and 38-45.6% in soluble and insoluble material, respectively, estimated after hydrolysis in 1 N NaOH. Enzymatic hydrolysis of IAA-labelled high molecular weight compounds gives free IAA and compound(s) corresponding to IAGlc isomers. These results suggest that 1-O-IAGlc synthesized in legume seeds may be used for the modification of some high molecular weight compounds.

Novel 1-O-indole-3-acetyl-β-d-glucose-dependent acyltransferase transferring indoleacetyl moiety to some mono- di- and oligosaccharides

“…In vitro experiments indicated that in maize seedlings and immature corn endosperm, the disproportionation of two 1-O-IAGlc molecules to generate di-O-(indole-3-acetyl)-D-glucose and the transfer of IAA moiety to some oligosaccharides from the raffinose family occur (Szmidt-Jaworska et al 1997;Leźnicki and Bandurski 2001). Furthermore, during the course of our previous studies, the transfer of IAA moiety from 1-O-IAGlc to high molecular acceptors was observed (Jakubowska and Kowalczyk 2004). On the other hand, the transfer of IAA moiety from IAInos to a monosaccharide (glucose, galactose, and mannose) as acceptor was demonstrated as well (Kowalczyk et al 2003).…”

“…More recently, the synthesis of di-O-(indole-3-acetyl)-D-glucose (disproportionation reaction) (Szmidt-Jaworska et al 1997), and the production of the ester conjugates with some sugars of the raffinose family have been reported (Leźnicki and Bandurski 2001). Moreover, the results of our earlier work suggested that 1-O-IAGlc synthesized in immature legume seeds may be a donor of IAA moiety for the modification of some high molecular weight compounds (Jakubowska and Kowalczyk 2004), supposedly 1 ? 4 cellulosic glucans or glycoproteins, earlier identified in maize and oat seeds (Piskornik and Bandurski 1972;Percival and Bandurski 1976).…”

“…one-half of the esters are the conjugates of IAA and cellulosic glucans (Piskornik and Bandurski 1972). The ester conjugates seem to predominate among monocotyledon plants (maize, rice), though their synthesis has also been found in Arabidopsis (Tam et al 2000), immature bean seeds (Bialek and Cohen 1989;Jakubowska and Kowalczyk 2004), Scots pine seeds (Ljung et al 2001), tomato pericarp (Catalá et al 1992), henbane cells (Oetiker and Aeschbacher 1997) or tobacco leaf protoplasts (Caboche et al 1984;Delbarre et al 1994).…”

A specific enzyme hydrolyzing 6-O(4-O)-indole-3-ylacetyl-β-d-glucose in immature kernels of Zea mays

“…Our preliminary feeding experiments indicated that [ 14 C] IAA is incorporated into a high molecular weight compounds, likely as in immature pea seeds (Jakubowska and Kowalczyk, 2004). They are hydrolyzed by endogenous hydrolytic enzymes to yield active auxin or lower molecular mass conjugates such as stable esters of IAA-glucose, IAAmyo-inositol and probably esters of IAA and trisaccharides from raffinose family.…”

Purification and Biochemical Characterization of Indole-3-acetyl-aspartic Acid Synthetase from Immature Seeds of Pea (Pisum sativum)

“…The highest activity of IAA-Asp synthetase remained in the supernatant after homogenate fractionation with 20% (w/v) concentration of PEG 6000. The failure of this enzyme to be precipitated by PEG can suggest a certain physical similarity to the enzyme catalyzing synthesis of the ester conjugate, 1-O-(indol-3-ylacetyl)-b-D-glucose (1-O-IAA-Glu) in maize kernels (Kowalczyk and Bandurski 1991) and legume seeds (Jakubowska and Kowalczyk 2004). Elution of the IAA-Asp synthetase activity at pH 7.6 required 250 mM NaCl concentration during DEAE-Sephacel anion-exchange chromatography, which points out a relatively low isoelectric point.…”