Promiscuous, non-catalytic, tandem carbohydrate-binding modules modulate the cell-wall structure and development of transgenic tobacco (Nicotiana tabacum) plants.
We have compared heterologous expression of two types of carbohydrate binding module (CBM) in tobacco cell walls. These are the promiscuous CBM29 modules (a tandem CBM29-1-2 and its single derivative CBM29-2), derived from a non-catalytic protein1, NCP1, of the Piromyces equi cellulase/hemicellulase complex, and the less promiscuous tandem CBM2b-1-2 from the Cellulomonas fimi xylanase 11A. CBM-labelling studies revealed that CBM29-1-2 binds indiscriminately to every tissue of the wild-type tobacco stem whereas binding of CBM2b-1-2 was restricted to vascular tissue. The promiscuous CBM29-1-2 had much more pronounced effects on transgenic tobacco plants than the less promiscuous CBM2b-1-2. Reduced stem elongation and prolonged juvenility, resulting in delayed flower development, were observed in transformants expressing CBM29-1-2 whereas such growth phenotypes were not observed for CBM2b-1-2 plants. Histological examination and electron microscopy revealed layers of collapsed cortical cells in the stems of CBM29-1-2 plants whereas cellular deformation in the stem cortical cells of CBM2b-1-2 transformants was less severe. Altered cell expansion was also observed in most parts of the CBM29-1-2 stem whereas for the CBM2b-1-2 stem this was observed in the xylem cells only. The cellulose content of the transgenic plants was not altered. These results support the hypothesis that CBMs can modify cell wall structure leading to modulation of wall loosening and plant growth.
Obembe
Olawole O
OO
Graduate School Experimental Plant Sciences, Laboratory of Plant Breeding, Wageningen University, PO Box 386, 6700 AJ, Wageningen, The Netherlands.
Jacobsen
Evert
E
Timmers
Jaap
J
Gilbert
Harry
H
Blake
Anthony W
AW
Knox
J Paul
JP
Visser
Richard G F
RG
Vincken
Jean-Paul
JP
D050260:Carbohydrate Metabolism / Q000235:genetics*; D017796:Caulimovirus / Q000235:genetics; D002473:Cell Wall / Q000378:metabolism* / Q000648:ultrastructure*; D040143:Cellulomonas / Q000235:genetics; D002482:Cellulose / Q000378:metabolism; D020285:Cryoelectron Microscopy; D015870:Gene Expression; D005798:Genes, Bacterial; D008855:Microscopy, Electron, Scanning; D020089:Piromyces / Q000235:genetics; D018547:Plant Stems / Q000254:growth & development / Q000378:metabolism / Q000648:ultrastructure; D030821:Plants, Genetically Modified / Q000254:growth & development / Q000378:metabolism* / Q000648:ultrastructure; D011401:Promoter Regions, Genetic; D014026:Nicotiana / Q000502:physiology* / Q000648:ultrastructure / Q000821:virology; D014170:Transformation, Genetic
D002482:Cellulose