Sucrose synthase is involved in the conversion of sucrose to polysaccharides in filamentous nitrogen-fixing cyanobacteria

L. CURATTI; L. GIARROCCO; A. CUMINO; G.L. SALERNO

PLANTA

Springer-Verlag

Lugar: Berlin Heidelberg; Año: 2008 vol. 228 p. 617 - 625

0032-0935

<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; mso-bidi-font-size:10.0pt; font-family:Arial; mso-fareast-font-family:"Times New Roman"; mso-bidi-font-family:"Times New Roman"; mso-ansi-language:ES; mso-fareast-language:EN-US;} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> Higher plants and cyanobacteria metabolize sucrose (Suc) by a similar set of enzymes. Suc synthase (SuS, UDP-glucose: D-fructose 2-a-D-glucosyl transferase, EC 2.4.1.13) catalyses the synthesis and cleavage of Suc and in higher plants, has an important role in polysaccharides biosynthesis and carbon allocation. In this work, we have studied the function of SuS regarding the metabolism of polysaccharides in filamentous nitrogen-fixing cyanobacteria. We show that the nitrogen and carbon sources and light regulate the expression of SuS encoding gene (susA), in a way that fits the pattern of polysaccharide content. Furthermore, the accumulation of glycogen was lower in an Anabaena sp. mutant strain with an insertion inactivation of susA under diazotrophic conditions while both glycogen and polysaccharides were higher in a mutant strain constitutively overexpressing susA. We also show that there are two forms of SuS in Anabaena, a soluble and a membrane-bound form. Taken together, these results strongly suggest that SuS is involved in the Suc to polysaccharides conversion according to nutritional and environmental signals in filamentous N2–fixing cyanobacteria.