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 = 0.05 and induction or repression of transcript levels by at least fourfold, we found that out of 30 171 probe sets on the microarray, 1345 probe sets were significantly affected by chilling in both control and CD-treated fruits, 509 probe sets were affected by chilling specifically in the CD-treated fruits, and 417 probe sets were specifically expressed in chilling-sensitive control fruits. Overall, exposure to chilling led to expression arrest of general cellular metabolic activity, including concretive down-regulation of cell wall, pathogen defence, photosynthesis, respiration, and protein, nucleic acid and secondary metabolism. On the other hand, chilling enhanced adaptation processes that involve changes in the expression of transcripts related to membranes, lipid, sterol and carbohydrate metabolism, stress stimuli, hormone biosynthesis, and modifications in DNA binding and transcription factors.

Transcript and metabolite profiling during cold acclimation of Arabidopsis reveals an intricate relationship of cold-regulated gene expression with modifications in metabolite content.

Exposure of Arabidopsis to low temperatures results in cold acclimation where freezing tolerance is enhanced. To achieve a wider view of the role of transcriptome to biochemical changes that occur during cold acclimation, analyses of concurrent transcript and metabolite changes during cold acclimation was performed revealing the dynamics of selected gene-metabolite relationships. Exposure to low temperature resulted in broad transcriptional and metabolite responses. Principal component analysis revealed sequentially progressive, global changes in both gene expression and metabolite profiles during cold acclimation. Changes in transcript abundance for many metabolic processes, including protein amino acid biosynthetic pathways and soluble carbohydrates, during cold acclimation were observed. For some metabolic processes, changes in transcript abundance temporally correlated with changes in metabolite levels. For other metabolic processes, changes in transcript levels were not correlated with changes in metabolite levels. The present findings demonstrate that regulatory processes independent of transcript abundance represent a key part of the metabolic adjustments that occur during cold acclimation.

Exogenous glucosamine globally protects chondrocytes from the arthritogenic effects of IL-1beta.

The effects of exogenous glucosamine on the biology of articular chondrocytes were determined by examining global transcription patterns under normal culture conditions and following challenge with IL-1beta. Chondrocytes isolated from the cartilage of rats were cultured in several flasks either alone or in the presence of 20 mM glucosamine. Six hours later, one-half of the cultures of each group were challenged with 10 ng/ml IL-1beta. Fourteen hours after this challenge, RNA was extracted from each culture individually and used to probe microarray chips corresponding to the entire rat genome. Glucosamine alone had no observable stimulatory effect on the transcription of primary cartilage matrix genes, such as aggrecan, collagen type II, or genes involved in glycosaminoglycan synthesis; however, glucosamine proved to be a potent, broad-spectrum inhibitor of IL-1beta. Of the 2,813 genes whose transcription was altered by IL-1beta stimulation (P < 0.0001), glucosamine significantly blocked the response in 2,055 (approximately 73%). Glucosamine fully protected the chondrocytes from IL-1-induced expression of inflammatory cytokines, chemokines, and growth factors as well as proteins involved in prostaglandin E2 and nitric oxide synthesis. It also blocked the IL-1-induced expression of matrix-specific proteases such as MMP-3, MMP-9, MMP-10, MMP-12, and ADAMTS-1. The concentrations of IL-1 and glucosamine used in these assays were supraphysiological and were not representative of the arthritic joint following oral consumption of glucosamine. They suggest, however, that the potential benefit of glucosamine in osteoarthritis is not related to cartilage matrix biosynthesis, but is more probably related to its ability to globally inhibit the deleterious effects of IL-1beta signaling. These results suggest that glucosamine, if administered effectively, may indeed have anti-arthritic properties, but primarily as an anti-inflammatory agent.