Role of alkaline/neutral invertases in Nostoc sp. PCC 7120

C.N. NISHI; L.E. GIARROCCO; W.A. VARGAS; G.L. SALERNO

Villa Carlos Paz, Cordoba, Argentina

Congreso; VI CONGRESO ARGENTINO DE MICROBIOLOGÍA GENERAL; 2009

Sociedad Argentina de Microbiología General SAMIGE

Sucrose (Suc), a key sugar in plant life, is also metabolized in cyanobacteria. These photosynthetic oxygen-evolving prokaryotes were shown to present proteins for Suc synthesis and degradation similar to enzymes from plants. Particularly, the hydrolysis of Suc can be performed by Alkaline/Neutral Invertases (A/N-Invs). Two A/N-Inv isoforms were biochemically characterized in Nostoc sp. PCC 7120, a filamentous nitrogen-fixing strain, and their encoding genes (invA and invB) were identified and functionally characterized. To elucidate the role of both proteins, insertional mutants lacking either InvA (invA- mutant) or InvB (invB- mutant) activity were generated. The phenotype of the mutants were studied and compared. Whereas invA- cultures were not affected, invB- cells stopped growing under diazotrophic conditions. On the other hand, a differential response to a salt treatment was obtained for both mutant strains. The localization of A/N-Invs in nitrogen-fixing filament cells was evidenced with transcriptional fusions of an optimized version of the green fluorescent protein (GFP) gene (gfp-mut2) to putative promoters of invA and invB. Contrary to previous report that proposed an exclusive heterocyst location (Schilling & Ehrnsperger, 1985), A/N-Invs were shown to locate in both the heterocysts and vegetative cells. Taken together these results show that InvA and InvB play distinct physiological functions, and that Suc hydrolysis by A/N-Inv is important for nitrogen fixation and to cope with sodium chloride stress. <!-- /* Font Definitions */ @font-face {font-family:"Cambria Math"; panose-1:2 4 5 3 5 4 6 3 2 4; mso-font-charset:0; mso-generic-font-family:roman; mso-font-pitch:variable; mso-font-signature:-1610611985 1107304683 0 0 159 0;} @font-face {font-family:Calibri; panose-1:2 15 5 2 2 2 4 3 2 4; mso-font-charset:0; mso-generic-font-family:swiss; mso-font-pitch:variable; mso-font-signature:-1610611985 1073750139 0 0 159 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-unhide:no; mso-style-qformat:yes; mso-style-parent:""; margin-top:0cm; margin-right:0cm; margin-bottom:10.0pt; margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-fareast-font-family:Calibri; mso-bidi-font-family:"Times New Roman"; mso-fareast-language:EN-US;} .MsoChpDefault {mso-style-type:export-only; mso-default-props:yes; font-size:10.0pt; mso-ansi-font-size:10.0pt; mso-bidi-font-size:10.0pt;} @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;} -->