Interlink between brassinosteroids and ethylene for the control of mitochondrial respiratory pathways in papaya fruit

MAZORRA, LUIS MIGUEL; GOES OLIVEIRA, MARCOS; FERNANDES SOUZA, ANDERSON; BATISTA DA SILVA, WILIAN; DOS SANTOS, GLÁUCIA M; ALMEIDA DA SILVA, LIGIA R; GOMES DA SILVA, MARCELO; BARTOLI, CARLOS GUILLERMO; GONCALVES DE OLIVEIRA, JURANDI

Rosario

Congreso; 8th International Conference for Plant Mitochondria Biology; 2013

The plant hormones brassinosteroids (BR) and ethylene (ET) act together regulating plant metabolism. We used BR and 1-methylcyclopropene (1-MCP, an inhibitor of ET action) to elucidate the interactions between both hormones for the regulation of mitochondrial respiratory pathways in papaya fruit. The exogenous application of the BR, 24-epibrasinolide (EBL), inhibited the activity of the cytochrome c oxidase (COX) in papaya fruit on either the first or the fifth day after treatment. By contrast, the EBL application enhanced the activity of the alternative oxidase (AOX) pathway. Treatment with brz2001 (BRZ, a specific inhibitor of BR synthesis) also reduced the COX activity and enhanced the AOX pathways. However, these effects were reduced in fruit treated simultaneously with EBL plus BRZ. Changing the BR level have no effect on the ET emission rate at the first 24 hours but a reduction in the emission of ET was observed in BRZ-treated fruit on the fifth day. EBL in combination with BRZ greatly increased ET production on the fifth day following the day on which the treatment was carried out. When ET sensitivity of fruit was inhibited by the application of 1-MCP, the effects of EBL and BRZ on the fruit were opposite to those obtained without 1-MCP. EBL increased the activity of the COX and slightly inhibited the AOX pathways in fruit pre-treated with 1-MCP. Ours data suggest that BR and ET act antagonistically to regulating the COX and AOX pathways during papaya fruit ripening.