Putative role of cytokinin in differential ethylene response of twolines of antisense ACC oxidase cantaloupe melons

Ciane Xavier Goncalves (1) , Aline Tiecher (1) , Fábio Clasen Chaves (1) , Leonardo Nora (1) , Li Zhengguo (2) , Alain Latché (3) , Jean-Claude Pech (3) , César Valmor Rombaldi (1)

1 UFPel - Universidade Federal de Pelotas = Federal University of Pelotas
2 Chongqing University [Chongqing]
3 GBF - Génomique et Biotechnologie des Fruits

Two transgenic lines of 'Cantaloupe' melon derived from the same wild type genotype were previouslygenerated using ACC oxidase antisense constructs from melon (pMEL1AS) and apple (pAP4AS). Both linesyielded fruit with reduced ethylene production and low ACC oxidase (ACCO) expression. ACCO antisensefruit also exhibited lower expression of ACC synthase genes, ACCS1 and ACCS3, indicating that these genesare positively regulated by ethylene and participate in the autocatalytic ethylene production process. Incontrast, a higher expression of ACCS5 was observed in antisense lines when compared to the wild typeindicating a negative feedback regulation of ACCS5 by ethylene. Fruit of both transformed lines exhibiteddelayed ripening and reduction in ester volatile production but differed in their response to exogenousethylene supply. While postharvest ethylene application fully restored the ripening process in pMEL1ASmelon, it only restored flesh softening of pAP4AS melon but not rind color change or aroma volatile pro-duction. Up-regulation of lipoxygenase pathway associated genes (hydroxyperoxide lyase, lipoxygenase,and alcohol acyl transferases 1, 3 and 4) occurred in ethylene-treated pMEL1AS fruit but not in pAP4ASmelons. Polygalacturonase1 gene transcript accumulation increased in pMEL1AS and pAP4AS fruit uponethylene supply. Zeatin and zeatin riboside content of roots and fruit (rind and flesh) of pAP4AS plantswere 5-fold higher than the wild type and pMEL1AS counterparts. Higher relative transcript accumula-tion of a gene involved in the cytokinin synthesis and a gene involved in cytokinin response were alsofound in the roots and fruit of pAP4AS. In addition, polyamines, which are known to reduce sensitiv-ity to ethylene, remained unchanged in all fruit. Collectively the results suggest a putative role for theincreased endogenous cytokinin content in counteracting ethylene action in some aspects of the fruitripening process.

Mots clés: Cucumis melo; Hormones; Fruit quality; Aroma; ACC synthase; ACC oxidasea

Domaines: Génétique

Ciane Xavier Goncalves, Aline Tiecher, Fábio Clasen Chaves, Leonardo Nora, Li Zhengguo, et al.. Putative role of cytokinin in differential ethylene response of twolines of antisense ACC oxidase cantaloupe melons. Postharvest Biology and Technology, 2013, vol. 86, pp. 511-519. ⟨10.1016/j.postharvbio.2013.07.040⟩. ⟨hal-00984967⟩