Effects Of Chilling On Tomato Fruit Ripening
The alteration of fruit ripening is a common chilling injury (CI) symptom in tomato. To evaluate whether tomato can be used as a model study for an altered fruit ripening associated with CI, the effect of chilling on fruit ripening have been investigated in tomato fruit cv. Trust (Solanum lycopersicum L.cv Trust) and tomato introgression line 11-2 (IL 11-2). Tomato fruit were harvested at breaker stage of maturity and ripened at 20 oC for up to 14 d, or stored at 3 oC for up to 4 weeks, and then ripened at 20 degrees C. In Trust tomato, the effects of chilling on fruit ripening were small, and the mealiness disorder was not detected. Chilling had a marked effect on gene expression, total activity, and protein accumulation of PG. However, pectin solubilization and depolymerization did not seem to be affected much by chilling. The expression of LeEXP1 was reduced by chilling, but LeEXP1 protein accumulation level was not affected. Post-transcriptional regulation of PG and LeEXP1 affected by chilling was observed. In IL 11-2 tomato, the effects of chilling on fruit ripening and the expression of ripening-related genes were investigated. Genes involved in color development: PSY1, CRTISO, GGPPS2, and DXS; cell-wall modification: PG, PE1, TBG4, LeEXP1, and XTH5; and volatile biosynthesis: TomloxC, ADH2, and ATT, were down-regulated by chilling. The alteration of ethylene production correlated with the altered ACS2, ACS4, and ACO1 expression. The expression of genes involved in ethylene signal transduction pathway such as LeETR1, NR, LeETR4, LeCTR1, LeEIL3, LeEIL4, and LeERF3 was altered by chilling. The gene expression of LeMADS-RIN, a ripening-regulated transcription factor, was down-regulated by chilling. The microarray analysis suggested other transcription factors may be involved in altered fruit ripening associated with CI. In conclusion, IL 11-2 tomato had the potential of being used as a model to study of the effects of chilling in fruit ripening. How chilling affects fruit ripening at the transcriptional and posttranscriptional levels should be studied in this tomato.
dissertation or thesis