Overexpression of the carbohydrate binding module of strawberry expansin2 in Arabidopsis thaliana modifies plant growth and cell wall metabolism

NARDI CRISTINA F.; VILLARREAL NATALIA M.; ROSSI FRANCO R.; MARTÍNEZ SANTIAGO; MARTÍNEZ GUSTAVO A.; CIVELLO PEDRO M.

PLANT MOLECULAR BIOLOGY

SPRINGER

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

0167-4412

Several  cell  wall  enzymes  are  carbohydrate  active  enzymes  that  contain  a  putative  Carbohydrate Binding Module (CBM) in their structures. The main function of these non-catalitic modules is to facilitate  the  interaction  between  the  enzyme  and  its  substrate.  Expansins  are  non-hydrolytic proteins present in the cell wall, and their structure includes a CBM in the C-terminal that bind to cell  wall  polymers  such  as  cellulose,  hemicelluloses  and  pectins.  We  studied  the  ability  of  the Expansin2 CBM (CBMFaEXP2) from strawberry (Fragaria x ananassa, Duch) to  modify the cell wall  of  Arabidopsis  thaliana.  Plants  overexpressing  CBMFaEXP2  were  characterized phenotypically and biochemically. Transgenic plants were taller than wild type, possibly owing to a faster  growth  of  the  main  stem.  Cell  walls  of  CBMFaEXP2-expressing  plants  were  thicker  and contained  higher  amount  of  pectins.    Lower  activity  of  a  set  of  enzymes  involved  in  cell  wall degradation (PG, β-Gal, β-Xyl)  was  found,  and  the  expression  of  the  corresponding  genes  (AtPG, Atβ-Gal, Atβ-Xyl5)  was  reduced  also.  In  addition,  a  decrease  in  the  expression  of  two A.  thaliana Expansin  genes  (AtEXP5 and AtEXP8)  was  observed.  Transgenic  plants  were  more  resistant  to Botrytis  cinerea infection  than  wild  type,  possibly  as  a  consequence  of  higher  cell  wall  integrity. Our results support the hypothesis that the overexpression of a putative CBM is able to modify plant cell wall structure leading to modulation of wall loosening and plant growth. These findings might offer a tool to controlling physiological processes where cell wall disassembly is relevant, such as fruit softening.