Submitted to: Plant Cell Tissue and Organ Culture
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/23/2009
Publication Date: 8/4/2009
Citation: Bae, H., Sicher Jr, R.C., Natarajan, S.S., Bailey, B.A. 2009. In situ expression of trehalose synthesizing genes, TPS1 and TPPB, in Arabidopsis thaliana using the GUS reporter gene. Plant Cell Tissue And Organ Culture. 98:311-319. Interpretive Summary: Plants use photosynthesis to make sugars from carbon dioxide, water and sunshine. However, due to rising carbon dioxide levels in the atmosphere there is a danger that many crop plants will make more sugars than can be used for their growth and energy needs. This condition is known as satiety. In contrast, low light and cold temperatures result in an inadequate sugar supply leading to starvation. Plants need to adjust to environmental conditions causing satiety or starvation by altering the activity of genes affecting the synthesis and use of sugars. Many scientists speculate that trehalose, which is similar to malt sugar and is present in trace amounts in higher plants, regulates rates of sugar formation and use in plants. In this study genetically modified plants were made that release a blue dye to indicate where genes for trehalose synthesis are located. These genes occurred at low levels throughout the plant but were concentrated in very young tissues and in flowers. This study also examined the effects of added sugars and of stress treatments on the activity of genes involved in trehalose synthesis and breakdown. The results showed that, in general, genes affecting trehalose levels in plants increased or decreased in response to the same stress treatments. These findings are consistent with the suggestion that the trehalose pathway in higher plants is involved in adjusting to stress. These results should be of interest to investigators interested in plant genetics and plant stress mechanisms.
Technical Abstract: Trehalose, a disaccharide of glucose that exists in most living organisms, functions as a storage carbohydrate and as a stress protectant in many microbionts. The function of trehalose in higher plants has yet to be determined. Trehalose 6-phosphate synthetase (TPS), trehalose 6-phosphate phosphatase (TPP) and the hydrolytic enzyme, altha-trehalase (TRE) are three specific enzymes that are involved in trehalose metabolism in higher plants. In the current study transgenic Arabidopsis lines were constructed that expressed the beta-glucuronidase (GUS) reporter gene using promoters for either AtTPS1 (At1g78580) or AtTPPB (At1g78090). GUS staining for both AtTPS1 and AtTPPB was detected in etiolated and in light grown seedlings. Both genes were expressed throughout the development of Arabidopsis. However, GUS staining was most visible in young, actively dividing tissues, in flowers and in tissues associated with assimilate transport. Quantitative real-time PCR (Q-PCR) techniques were used to examine the expression of AtTPS1, AtTPPB and AtTRE transcripts in response to various chemical and abiotic stress treatments. All three genes were either unchanged or were repressed by feeding sucrose, glucose, fructose and trehalose to seedlings in liquid culture. As opposed to sugars, sorbitol strongly induced AtTPPB expression. Also, transcripts for all three trehalose pathway genes were induced by ABA, mannitol and NaCl. These findings suggested that the expression of genes involved in trehalose synthesis was coordinated in Arabidopsis both during development and in response to specific chemical or stress treatments.