| 20237022 |
Tacken E, Ireland H, Gunaseelan K, Karunairetnam S, Wang D, Schultz K, Bowen J, Atkinson RG, Johnston JW, Putterill J, Hellens RP, Schaffer RJ: The role of ethylene and cold temperature in the regulation of the apple POLYGALACTURONASE 1 gene and fruit softening. Plant Physiol. 2010 Mar 17.
Fruit softening in apples is associated with an increase in the ripening hormone ethylene. Here we show that in 'Royal Gala' apples that have the ethylene biosynthetic gene ACC OXIDASE1 (ACO1) suppressed, a cold treatment pre-conditions the apples to soften independently of added ethylene. When a cold treatment is followed by an ethylene treatment, a more rapid softening occurs than in apples that have not had a cold treatment. Apple fruit softening has been associated with the increase in expression of cell wall hydrolase genes. One such gene POLYGALACTURONASE 1 (PG1) increases in expression with both ethylene and following a cold treatment. Transcriptional regulation of PG1 through the ethylene pathway is likely to be through an ETHYLENE INSENSITIVE 3-like (EIN3-like) transcription factor, which increases in expression during apple fruit development and transactivates the PG1 promoter in transient assays in the presence of ethylene. A cold-related gene that resembles a COLD BINDING FACTOR (CBF) class of gene also transactivates the PG1 promoter. The transactivation by the CBF-like gene is greatly enhanced by the addition of exogenous ethylene. These observations give a possible molecular mechanism for the cold- and ethylene-regulated control of fruit softening, and suggest that either these two pathways act independently and synergistically with each other, or cold enhances the ethylene response such that background levels of ethylene in the ethylene-suppressed apples is sufficient to induce fruit softening in apples. |
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