Genetic Engineering of the Biosynthesis of Glycinebetaine Enhances Photosynthesis against High Temperature Stress in Transgenic Tobacco Plants

Abstract

Genetically engineered tobacco (Nicotiana tabacum) with the ability to synthesis glycinebetaine was established by introducing the BADH gene for betaine aldehyde dehydrogenase from spinach (Spinacia oleracea). The genetic engineering enabled the plants to accumulate glycinebetaine mainly in chloroplasts and resulted in enhanced tolerance to high temperature stress during growth of young seedlings. Moreover, CO 2 assimilation of transgenic plants was significantly more tolerant to high temperatures than that of wild-type plants. The analyses of chlorophyll fluorescence and the activation of Rubisco indicated that the enhancement of photosynthesis to high temperatures was not related to the function of photosystem II but to the Rubisco activase-mediated activation of Rubisco. Western-blotting analyses showed that high temperature stress led to the association of Rubisco activase with the thylakoid membranes from the stroma fractions. However, such an association was much more pronounced in wild-type plants than in transgenic plants. The results in this study suggest that under high temperature stress, glycinebetaine maintains the activation of Rubisco by preventing the sequestration of Rubisco activase to the thylakoid membranes from the soluble stroma fractions and thus enhances the tolerance of CO 2 assimilation to high temperature stress. The results seem to suggest that engineering of the biosynthesis of glycinebetaine by transformation with the BADH gene might be an effective method for enhancing high temperature tolerance of plants.High temperature stress is one of the environmental factors that limit plant growth (Levitt, 1980;Boyer, 1982;Frova, 1997). Photosynthesis is one of the physiological processes that are most sensitive to high temperature stress (Berry and Bjö rkman, 1980). Inhibition of photosynthesis by high temperature stress is a common occurrence for plants in tropical and subtropical regions and the temperate zones where plants are exposed periodically to high temperatures (Larcher, 1995). It is well documented that high temperature stress causes damage to photosynthetic electron transport (Berry and Björkman, 1980). For many years, PSII has long been considered the most heatsensitive component of the photosynthetic apparatus (Berry and Bjö rkman, 1980). However, it appears that PSII is unaffected at temperatures that inhibit CO 2 fixation (Weis, 1981a(Weis, , 1981b, and that PSII is only inhibited by severe heat stress when the temperature is higher than 45°C (Havaux, 1993(Havaux, , 1996. Recent studies seem to support that PSII activity is not limiting at temperatures that inhibit CO 2 fixation and that CO 2 fixation is most sensitive to heat stress due to the inhibition of activation of Rubisco via a direct effect on Rubisco activase (Feller et al., 1998; Crafts-Brandner, 2004a, 2004b;Haldimann and Feller, 2004).Glycinebetaine (GB) is one of the organic compatible solutes that can accumulate rapidly in many plants under salinity stress, drought, and low temperature (McCue and Hanson, 1990...

Genetic engineering of glycine betaine biosynthesis to enhance abiotic stress tolerance in plants

“…It is possible that the extreme-temperature tolerance induced in transgenic Arabidopsis is due to the protection of Rubisco activase by GB. This finding was further supported by the increased photosynthetic activity in BADH-transgenic tobacco (Yang et al 2005). The physiological basis for the enhanced tolerance of growth to high-temperature stress (25-45°C) in transgenic tobacco might be associated with an increased tolerance of photosynthesis to high temperatures.…”

“…The physiological basis for the enhanced tolerance of growth to high-temperature stress (25-45°C) in transgenic tobacco might be associated with an increased tolerance of photosynthesis to high temperatures. Moderately high temperatures do not affect the activity or efficiency of PSII, and the enhanced CO 2 assimilation rate induced by GB is associated with the Rubisco activase-mediated activation of Rubisco (Yang et al 2005). The accumulation of GB increases the tolerance of Rubisco activase to high temperatures that results in enhanced tolerance of CO 2 assimilation in transgenic plants as compared to the wild type controls.…”

“…Recently, Yang et al (2005) reported that exogenous application of GB improved growth and CO 2 assimilation in maize plants under salt stress. Salt stress induced a significant decrease in the actual efficiency of PSII, whereas GB application resulted in a smaller decrease in the efficiency of PSII in salt-stressed maize plants.…”

Genetic engineering for heat tolerance in plants

“…Overproduction of glycinebetaine also provided significant advantage to the growth of young transgenic seedlings at supra-optimal temperature in this study. Yang et al (2005) overexpressed betaine aldehyde dehydrogenase protein from spinach into tobacco plants, to increase glycinebetaine levels. Tobacco transformants in this study showed increased thermotolerance in terms of growth of young seedlings as well as CO 2 assimilation rates.…”

Raising salinity tolerant rice: recent progress and future perspectives

“…In contrast to each of these two pathways that involved two enzymes, the biosynthesis of GB is catalysed by a single flavoenzyme choline oxidase (COD) in certain microorganisms such as the soil bacterium Arthrobacter globiformis (Ikuta et al, 1977). To achieve tolerance against various abiotic stresses, overexpression of BADH (Moghaieb et al, 2000;Kumar et al, 2004;Yang et al, 2005), CDH (Lilius et al, 1996;Quan et al, 2004) has been carried out in several plant species. Overexpression of coda gene encoding COD has been most widely attempted to develop abiotic stress tolerant transgenic plants (Hayashi et al, 1997;Alia et al, 1998;Huang et al, 2000, Sulpice et al, 2003Parvanova et al, 2004;Prasad and Pardha-Saradhi, 2004).…”