Transcriptome profiling of grapefruit flavedo following exposure to low temperature and conditioning treatments uncovers principal molecular components involved in chilling tolerance and susceptibility.

A pre-storage conditioning (CD) treatment of 16 degrees C for 7 d enhanced chilling tolerance of grapefruit and reduced the development of chilling injuries during storage at 5 degrees C. To gain a better understanding of the molecular mechanisms involved in the responses of citrus fruit to low temperatures, we performed genome-wide transcriptional profiling analysis of RNA isolated from grapefruit flavedo using the newly developed Affymetrix Citrus GeneChip microarray. Utilizing very restrictive cut-off criteria, including pair-wise anova comparisons significantly different at P < or = 0.

Postharvest heat and conditioning treatments activate different molecular responses and reduce chilling injuries in grapefruit.

A combination of hot water (a rinse at 62 degrees C for 20 s) and conditioning (pre-storage at 16 degrees C for 7 d) treatments synergistically reduced chilling injury development in grapefruit (Citrus paradisi, cv. "Star Ruby") during cold storage at 2 degrees C, suggesting that the treatments may activate different chilling tolerance responses. To study the molecular mechanisms involved, chilling- and conditioning-responsive genes were isolated by polymerase chain reaction (PCR) cDNA subtraction, cDNA libraries were constructed from hot water- and conditioning-treated fruit, and cDNA sequencing was used to identify putative stress-responsive and chilling tolerance genes.