Tobacco Transgenic Lines That Express Fenugreek Galactomannan Galactosyltransferase Constitutively Have Structurally Altered Galactomannans in Their Seed Endosperm Cell Walls1

AUTOR(ES)

Reid, J.S. Grant

FONTE

American Society of Plant Biologists

RESUMO

Galactomannans [(1→6)-α-d-galactose (Gal)-substituted (1→4)-β-d-mannans] are major cell wall storage polysaccharides in the endosperms of some seeds, notably the legumes. Their biosynthesis in developing legume seeds involves the functional interaction of two membrane-bound glycosyltransferases, mannan synthase (MS) and galactomannan galactosyltransferase (GMGT). MS catalyzes the elongation of the mannan backbone, whereas GMGT action determines the distribution and amount of Gal substitution. Fenugreek (Trigonella foenum-graecum) forms a galactomannan with a very high degree of Gal substitution (Man/Gal = 1.1), and its GMGT has been characterized. We now report that the endosperm cell walls of the tobacco (Nicotiana tabacum) seed are rich in a galactomannan with a very low degree of Gal substitution (Man/Gal about 20) and that its depositional time course is closely correlated with membrane-bound MS and GMGT activities. Furthermore, we demonstrate that seeds from transgenic tobacco lines that express fenugreek GMGT constitutively in membrane-bound form have endosperm galactomannans with increased average degrees of Gal substitution (Man/Gal about 10 in T1 generation seeds and about 7.5 in T2 generation seeds). Membrane-bound enzyme systems from transgenic seed endosperms form galactomannans in vitro that are more highly Gal substituted than those formed by controls under identical conditions. To our knowledge, this is the first report of structural manipulation of a plant cell wall polysaccharide in transgenic plants via a biosynthetic membrane-bound glycosyltransferase.

Documentos Relacionados

• The Seeds of Lotus japonicus Lines Transformed with Sense, Antisense, and Sense/Antisense Galactomannan Galactosyltransferase Constructs Have Structurally Altered Galactomannans in Their Endosperm Cell Walls1
• Transfer Specificity of Detergent-Solubilized Fenugreek Galactomannan Galactosyltransferase
• Studies of Streptococcal Cell Walls VII. Carbohydrate Composition of Group B Cell Walls1
• Lines of BPV-transformed murine cells that constitutively express influenza virus hemagglutinin.
• Protection against tobacco mosaic virus in transgenic plants that express tobacco mosaic virus antisense RNA.