Overexpression of a grapevine R2R3-MYB factor in tomato affects vegetative development, flower morphology and flavonoid and terpenoid metabolism.
Although the terpenoid pathway constitutes, with the phenylpropanoid metabolism, the major pathway of secondary metabolism in plants, little is known about its regulation. Overexpression of a Vitis vinifera R2R3-MYB transcription factor (VvMYB5b) in tomato induced pleiotropic changes including dwarfism, modified leaf structure, alterations of floral morphology, pigmented and glossy fruits at the "green-mature" stage and impaired seed germination. Two main branches of secondary metabolism, which profoundly influence the organoleptic properties of the fruit, were affected in the opposite way by VvMYB5b overexpression. Phenylpropanoid metabolism was down regulated whereas the amount of beta-carotene was up regulated. This is the first example of the independent regulation of phenylpropanoid and carotenoid metabolism. The strongest modification concerns a decrease in beta-amyrin, the precursor of the oleanolic acid, which is the major component of grape waxes. Scanning electron microscopy analysis of fruits and leaves confirms the alteration of wax metabolism and a modification of cell size and shape. This may potentially impact resistance/tolerance to biotic and abiotic stresses. The results are compared with a similar approach using heterologous expression of VvMYB5b in tobacco.
Mahjoub
Ali
A
UMR 1287 Ecophysiology and Grape Functional Genomics, University of Bordeaux, INRA, Institut des Sciences de la Vigne et du Vin, 210 Chemin de Leysotte, CS 50008, 33883 Villenave d'Ornon, France.
Hernould
Michel
M
Joubès
Jérôme
J
Decendit
Alain
A
Mars
Mohamed
M
Barrieu
François
F
Hamdi
Saïd
S
Delrot
Serge
S
D005419:Flavonoids / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D018551:Solanum lycopersicum / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D009828:Oleanolic Acid / Q000031:analogs & derivatives / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018514:Plant Structures / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D020005:Propanols / Q000378:metabolism*; D013729:Terpenes / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D014885:Waxes / Q000378:metabolism; D019207:beta Carotene / Q000235:genetics / Q000378:metabolism*
D005419:Flavonoids; D010940:Plant Proteins; D020005:Propanols; D013729:Terpenes; D014157:Transcription Factors; D014885:Waxes; D019207:beta Carotene; C439395:1-phenylpropanol; D009828:Oleanolic Acid