Submitted to: Plant Physiology and Biochemistry
Publication Type: Abstract Only
Publication Acceptance Date: July 15, 2000
Publication Date: N/A
Technical Abstract: In tomato, impaired reductive activation of the stromal bisphosphatases appears to be the dominating factor limiting carbon assimilation following chilling in the light. The illumination-dependent activation of at least seven different chloroplast enzymes involves the reversible thiol/disulfide exchange between thioredoxin and the photosynthetic enzyme. The thermodynamics of the thiol/disulfide exchange between thioredoxin and the regulatory sulfhydryl groups of the various light-regulated chloroplast enzymes explains the differential responses among the various thioredoxin-regulated enzymes to the effects of chilling in the light (Hutchison et al. 2000). In the case of dark chilling, an intriguing effect of low temperature on the circadian regulation of transcription indicates that the low-temperature induced inhibition of photosynthesis in tomato may result from the loss of coordination in the expression of critical enzymes controlling photosynthetic metabolism. In tomato, low-temperature treatment delays the progress of the circadian clock regulating the transcription of certain nuclear-encoded genes including those for cab and rca. The clock stops for the duration of the chilling treatment and resumes upon rewarming, but the affected rhythms are then out of phase with the actual time of day.