JOURNAL ARTICLE

Cloning, functional expression, and characterization of the raffinose oligosaccharide chain elongation enzyme, galactan:galactan galactosyltransferase, from common bugle leaves

Esther M Tapernoux-Lüthi, Andreas Böhm, Felix Keller
Plant Physiology 2004, 134 (4): 1377-87
15034167
Galactan:galactan galactosyltransferase (GGT) is a unique enzyme of the raffinose family oligosaccharide (RFO) biosynthetic pathway. It catalyzes the chain elongation of RFOs without using galactinol (alpha-galactosyl-myoinositol) by simply transferring a terminal alpha-galactosyl residue from one RFO molecule to another one. Here, we report the cloning and functional expression of a cDNA encoding GGT from leaves of the common bugle (Ajuga reptans), a winter-hardy long-chain RFO-storing Lamiaceae. The cDNA comprises an open reading frame of 1215 bp. Expression in tobacco (Nicotiana plumbaginifolia) protoplasts resulted in a functional recombinant protein, which showed GGT activity like the previously described purified, native GGT enzyme. At the amino acid level, GGT shows high homologies (>60%) to acid plant alpha-galactosidases of the family 27 of glycosylhydrolases. It is clearly distinct from the family 36 of glycosylhydrolases, which harbor galactinol-dependent raffinose and stachyose synthases as well as alkaline alpha-galactosidases. Physiological studies on the role of GGT confirmed that GGT plays a key role in RFO chain elongation and carbon storage. When excised leaves were exposed to chilling temperatures, levels of GGT transcripts, enzyme activities, and long-chain RFO concentrations increased concomitantly. On a whole-plant level, chilling temperatures induced GGT expression mainly in the roots and fully developed leaves, both known RFO storage organs of the common bugle, indicating an adaptation of the metabolism from active growth to transient storage in the cold.

Full Text Links

Find Full Text Links for this Article

Discussion

You are not logged in. Sign Up or Log In to join the discussion.

Related Papers

Remove bar
Read by QxMD icon Read
15034167
×

Save your favorite articles in one place with a free QxMD account.

×

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"