OVEREXPRESSION OF THE CARBOHYDRATE BINDING MODULE OF STRAWBERRY EXPANSIN2 IN ARABIDOPSIS THALIANA MODIFIES PLANT GROWTH AND CELL WALL METABOLISM

CRISTINA F. NARDI; NATALIA M. VILLARREAL; FRANCO ROSSI; SANTIAGO M. MARTÍNEZ ALONSO

PLANT MOLECULAR BIOLOGY

SPRINGER

Lugar: Berlin; Año: 2015 vol. 88 p. 101 - 117

0167-4412

Several cell wall enzymes are carbohydrateactive enzymes that contain a putative Carbohydrate BindingModule (CBM) in their structures. The main functionof these non-catalitic modules is to facilitate the interactionbetween the enzyme and its substrate. Expansins are nonhydrolyticproteins present in the cell wall, and their structureincludes a CBM in the C-terminal that bind to cell wallpolymers such as cellulose, hemicelluloses and pectins. Westudied the ability of the Expansin2 CBM (CBMFaEXP2)from strawberry (Fragaria x ananassa, Duch) to modifythe cell wall of Arabidopsis thaliana. Plants overexpressingCBMFaEXP2 were characterized phenotypically andbiochemically. Transgenic plants were taller than wild type,possibly owing to a faster growth of the main stem. Cellwalls of CBMFaEXP2-expressing plants were thicker andcontained higher amount of pectins. Lower activity of a setof enzymes involved in cell wall degradation (PG, β-Gal,β-Xyl) was found, and the expression of the correspondinggenes (AtPG, Atβ-Gal, Atβ-Xyl5) was reduced also.In addition, a decrease in the expression of two A. thalianaExpansin genes (AtEXP5 and AtEXP8) was observed.Transgenic plants were more resistant to Botrytis cinereainfection than wild type, possibly as a consequence ofhigher cell wall integrity. Our results support the hypothesisthat the overexpression of a putative CBM is able to modifyplant cell wall structure leading to modulation of wall looseningand plant growth. These findings might offer a tool tocontrolling physiological processes where cell wall disassemblyis relevant, such as fruit softening.