|Fung, Raymond W|
Submitted to: Journal of Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/9/2005
Publication Date: 4/1/2006
Citation: Fung, R.M., Wang, C.Y., Smith, D.L., Gross, K.C., Tao, Y., Tian, M. 2006. Characterization of leaox gene expression in response to mesa and meja pre-treatment and low temperature in pink tomatoes (lycopersicon esculentum). Journal of Plant Physiology. 163:1049-1060. Interpretive Summary: Tomatoes are susceptible to chilling injury when stored below 10°C. Damage caused by low temperatures can severely reduce the quality and storage life of these products. We found that treatments with some natural volatile compounds increased the resistance of tomatoes and peppers to chilling injury. Because of the potential usefulness of volatile vapors in extending postharvest longevity of produce, it is important to understand the mechanisms involved. We found that volatile vapor treatments increased the levels of transcripts of antioxidative enzymes. These results suggest that the treatment of tomatoes with volatile vapors induces the synthesis of some stress proteins, which leads to increased chilling tolerance and resistance to decay. The genes for one group of these enzymes were identified, sequenced and characterized. Understanding the function of these genes is one method to help identify more and optimize existing treatments to alleviate chilling injury. The work presented here points to the possibility of using plant-derived compounds to naturally activate fruit protection before low temperature storage. This information is useful to other scientist as well as the produce industry, and will ultimately benefit consumers.
Technical Abstract: Methyl salicylate (MeSA) vapour increased resistance against chilling injury (CI) in freshly harvested pink tomatoes (Lycopersicon esculentum L. cv. Beefsteak). The expression patterns of alternative oxidase (AOX) before and during the chilling period demonstrated that pre-treatment of tomato fruit with MeSA vapor increased the transcript levels of AOX. We used 4 EST tomato clones of AOX from the public database that belong to two distinctly related families, 1 and 2 defined in plants. Three clones were designated as LeAOX1a, 1b and 1c and the fourth clone as LeAOX2. Using RT-PCR, 1a and 1b clones were expressed in leaf, root and fruit tissues, but 1c was expressed preferentially in roots. RNA transcript from LeAOX1a of AOX subfamily 1 was present in much greater abundance than 1b or 1c. The presence of longer AOX transcripts detected by Northern analysis in cold-stored tomato fruit was confirmed to be the un-spliced pre-mRNA transcripts of LeAOX1a and LeAOX1b genes. Intron splicing of LeAOX1c gene was also affected by cold storage when it was detected in roots. Altered intron splicing of AOX pre-mRNAs did not relate to mRNA abundance. Transcript levels of key genes involved in RNA processing (splicing factors: 9G8-SR and SF2-SR, fibrillarin and DEAD box RNA helicase) were altered by changes in storage temperature. The inhibition of AOX intron splicing and its relationship with the change in expression of RNA processing enzymes in cold stored tomato fruit was discussed.