Indole-3-acetic acid, ethylene, and abscisic acid metabolism in developing muskmelon (Cucumis melo L.) fruit

Abstract

Hormonal metabolism associated with fruit development in muskmelon was investigated by measuring IAA, ABA, and ACC levels in several tissues at various stages of development. In addition, levels of conjugated IAA and ABA were determined in the same tissues. Ethylene production, which is believed to signal the ripening and senescence of mature fruit, was also measured. Ethylene production was highest in the outer tissue near the rind and gradually declined during maturation, except for a dramatic increase in all fruit tissues at the climacteric. In contrast to ethylene production, ACC levels increased during maturation and remained equal throughout the fruit until the climacteric, when levels in the outer tissues increased nearly 5-fold over levels in the inner tissues. The consistent presence of ACC indicates that ACC oxidase rather than the availability of ACC regulates ethylene production in developing fruits. ABA and ABA esters generally declined during maturation, however an increase in ABA esters associated with the outer mesocarp tissue was observed in fully mature, climacteric fruit. IAA and IAA conjugates were only found in the outer tissue near the rind, and their levels remained low until the fruit was fully mature and entering the climacteric. At that time, increased levels of conjugates were detected. The late burst of hormonal metabolism in the outer mesocarp tissue appeared to signal its degeneration and the deterioration that typically occurs in ripening fruit. The tissue-specific conjugation of IAA and ABA, in addition to the production of climacteric ethylene, may represent part of the signaling mechanism initiating ripening and eventual deterioration of tissues in muskmelon fruits.Abbreviations: ABA = abscisic acid; ACC = 1 -aminocylopropane-1 -carboxylic acid; DAP = days after pollination; IAA = indole-3-acetic acid

Chlorophenoxyacetic acid and chloropyridylphenylurea accelerate translocation of photoassimilates to parthenocarpic and seeded fruits of muskmelon (Cucumis melo)

“…Therefore the effect of CPPU was not maintained, indicating that normal seeds were important for fruit development. No further information is available about endogenous hormones in melon seeds, although Dunlap et al (1996) has reported about IAA, ethylene and ABA metabolism in developing muskmelon fruit. In earlier studies we reported that CPPU treatment increases endogenous IAA content and decreases endogenous ABA content and also that CPPU promotes invertase activity in seeded melon fruit during the early growth stage (Hayata et al, 2001a).…”

Interactions between ethylene and auxin are crucial to the control of grape (Vitis vinifera L.) berry ripening

“…In all four fruit species mentioned above, as well as in many other climacteric and non-climacteric fruit, the application of natural or synthetic auxins during the pre-ripening stage of fruit development has often been found to lead to a ripening delay (reviewed by [ 6 ]) and therefore auxins are widely viewed as ripening inhibitors [ 24 , 26 , 29 , 33 ]. In contrast IAA-amide conjugates have been reported to accumulate in ripening bananas [ 26 ], muskmelons ( Cucumis melo L.) [ 34 ] and strawberries [ 27 ]. More detailed studies in grape berries have revealed that the concentration of IAA-Asp, an IAA-amide conjugate linked to IAA degradation [ 35 ] and formed by the action of IAA-amido synthetases (Gretchen Hagen (GH3) proteins) [ 36 ], increased sharply at veraison and remained at high concentrations throughout the ripening phase [ 29 ].…”

Partial Purification and Characterization of an Inducible Indole-3-Acetyl-L-Aspartic Acid Hydrolase from Enterobacter agglomerans

“…IAA-Asp is known to be an endogenous component of soybean seeds (Cohen, 1982), and available evidence indicates that it is present in many other plant species (Row et al, 1961;Olney, 1968;Tillberg, 1974;Andersson and Sandberg, 1982;Cohen and Ernstsen, 1991;Dunlap et al, 1996). However, despite its widespread existence in plants and two hopeful preliminary reports (Lantican and Muir, 1967;Higgins and Barnett, 1976), an in vitro system for IAA-Asp synthesis or hydrolysis by an enzymatic mechanism has yet to be achieved (Bandurski et al, 1995).…”