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Distinct regulation of sucrose: sucrose‐1‐fructosyltransferase (1‐SST) and sucrose: fructan‐6‐fructosyltransferase (6‐SFT), the key enzymes of fructan synthesis in barley leaves: 1‐SST as the pacemaker
Author(s) -
Nagaraj Vinay J.,
Altenbach Denise,
Galati Virginie,
Lüscher Marcel,
Meyer Alain D.,
Boller Thomas,
Wiemken Andres
Publication year - 2004
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.2004.00995.x
Subject(s) - fructan , sucrose , hordeum vulgare , biology , enzyme , biochemistry , poaceae , botany
Summary• Previously we have cloned sucrose: fructan‐6‐fructosyltransferase (6‐SFT) from barley ( Hordeum vulgare ) and proposed that synthesis of fructans in grasses depends on the concerted action of two main enzymes: sucrose: sucrose‐1‐fructosyltransferase (1‐SST), as in other fructan producing plants, and 6‐SFT, found only in grasses. • Here we report the cloning of barley 1‐SST, verifying the activity of the encoded protein by expression in Pichia pastoris . As expected, the barley 1‐SST is homologous to invertases and fructosyltransferases, and in particular to barley 6‐SFT. • The gene expression pattern of 1‐SST and 6‐SFT, along with the corresponding enzyme activities and fructan levels, were investigated in excised barley leaves subjected to a light–dark regime known to sequentially induce fructan accumulation and mobilization. The turnover of transcripts and enzyme activities of 1‐SST and 6‐SFT was compared, using appropriate inhibitors. • We found the 1‐SST transcripts and enzymatic activity respond quickly, being subject to a rapid turnover. By contrast, the 6‐SFT transcripts and enzymatic activity were found to be much more stable. The much higher responsiveness of 1‐SST to regulatory processes, as compared with 6‐SFT, clearly indicates that 1‐SST plays the role of the pacemaker enzyme of fructan synthesis in barley leaves.