Impact of brassinosteroids and ethylene on ascorbic acid accumulation in tomato leaves

LUIS MIGUEL MAZORRA MORALES; MARÍA EUGENIA SENN; GUSTAVO ESTEBAN GERGOFF GROZEFF; DIEGO DARÍO FANELLO; CRISTIAN ANTONIO CARRIÓN; MIRIAM NÚÑEZ; GERARD JAMES BISHOP; CARLOS GUILLERMO BARTOLI

PLANT PHYSIOLOGY AND BIOCHEMISTRY

ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER

Lugar: Paris; Año: 2014 vol. 74

0981-9428

Plant steroid hormones brassinosteroids (BRs) and the gaseous hormone ethylene (ET) alter the ascorbicacideglutathione (AAeGSH) levels in tomato (Solanum lycopersicum L.) plants. The interaction of thesehormones in regulating antioxidant metabolism is however unknown. The combined use of genetics (BRmutants)and chemical application (BR/ET-related chemicals) shows that BRs and ET signalling pathwaysinteract, to regulate leaf AA content and synthesis. BR-deficient (dx) leaves display low total AA but BRaccumulating(35S:D) leaves show normal total AA content. Leaves with either BR levels lower or higherthan wild type plants showed a higher oxidised AA redox state. The activity of L-galactono-1,4-lactonedehydrogenase (L-GalLDH), the mitochondrial enzyme that catalyses the last step in AA synthesis islower in dx and higher in 35S:D plants. BR-deficient mutants show higher ET production but it is restoredto normal levels when BR content is increased in 35S:D plants. Suppression of ET signalling using 1-methylcyclopropene in dx and 35S:D plants restored leaf AA content and L-GalLDH activity, to thevalues observed in wild type. The suppression of ET action in dx and 35S:D leaves leads to the respectivedecreasing and increasing respiration, indicating an opposite response compared to AA synthesis. Thisinverse relationship is lacking in ET suppressed dx plants in response to external BRs. The modificationsin the in vivo activity of L-GalLDH activity do not correlate with changes in the level of the enzyme. Takentogether, these data suggest that ET suppresses and BRs promote AA synthesis and accumulation.